Human Biology
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
Biologically speaking
Humans, like other living things, are highly organized. Cells form tissues, which form organs
that function in organ systems. Humans come into existence through reproduction, growth, and
development. Unlike other living things, humans have a cultural background that sometimes
hinders the belief that they are the product of an evolutionary process. Human beings are
vertebrates closely related to the apes. Human beings are also part of the biosphere where
populations interact with the physical environment and with each other. Human activities
threaten the existence of ecosystems like tropical rain forests. Biodiversity is now being
decreased at a rapid rate.
The process of science
When studying the world of living things, biologists, like other scientists, use the scientific
method, which consists of these steps: making an observation, formulating a hypothesis, carrying
out an experiment or simply making further observations, and coming to a conclusion.
Science and social responsibility
It is the responsibility of all to make ethical and moral decisions about how best to utilize the
results of scientific investigations.
Elements and atoms
All matter consists of some 92 elements. Each element is made of just one type of atom. An
atom has a weight, which is dependent on the number of protons and neutrons in the nucleus, and
its chemical properties are dependent on the number of electrons in the outer shell.
Molecules and compounds
Atoms react with each other through forming ionic bonds or covalent bonds. Ionic bonds are
an attraction between charged ions. Atoms share electrons in covalent bonds, which can be
single, double, or triple bonds.
Water and living things
Water, acids, and bases are important inorganic molecules. The polarity of water accounts for
it being the universal solvent; hydrogen bonding accounts for it boiling at 100°C and freezing at
0°C. Because it is slow to heat up and slow to freeze, water is liquid at the temperature of living
things. Pure water has a neutral pH; acids increase the hydrogen ion concentration [H+] but
lower the pH, and bases decrease the hydrogen ion concentration [H+] but increase the pH of
water.
Molecules of life
The chemistry of carbon accounts for the chemistry of organic compounds. Carbohydrates,
lipids, proteins, and nucleic acids are molecules with specific functions in cells.
Carbohydrates
Glucose is the 6-carbon sugar most used by cells for “quick” energy. Like the rest of the
macromolecules to be studied, condensation synthesis joins two or more sugars, and a hydrolysis
reaction splits the bond. Plants store glucose as starch, and animals store glucose as glycogen.
Humans cannot digest cellulose, which forms plant cell walls.
Lipids
Lipids are varied in structure and function. Fats and oils, which function in long-term energy
storage, contain glycerol and three fatty acids. Fatty acids can be saturated or unsaturated.
Plasma membranes contain phospholipids that have a polarized end. Certain hormones are
derived from cholesterol, a complex ring compound.
Proteins
The primary structure of a polypeptide is its own particular sequence of the possible 20 types
of amino acids. The secondary structure is often an alpha (α) helix. The tertiary structure occurs
when a polypeptide bends and twists into a three-dimensional shape. A protein can contain
several polypeptides, and this accounts for a possible quaternary structure.
Nucleic acids
Nucleic acids are polymers of nucleotides. Each nucleotide has three components: a sugar, a
base, and phosphate (phosphoric acid). DNA, which contains the sugar deoxyribose, is the
genetic material that stores information for its own replication and for the order in which amino
acids are to be sequenced in proteins. DNA, with the help of RNA, specifies protein synthesis.
ATP, with its unstable phosphate bonds, is the energy currency of cells. Hydrolysis of ATP to
ADP + P releases energy that is used by the cell to do metabolic work.
Cell size
Cells are quite small, and it usually takes a microscope to see them. Small cubes, like cells,
have a more favorable surface/volume ratio than do large cubes. Only inactive eggs are large
enough to be seen by the naked eye; once development starts, cell division results in small-size
cells.
Cellular organization
A cell is surrounded by a plasma membrane, which regulates the entrance and exit of
molecules and ions. Some molecules, such as water and gases, diffuse through the membrane.
The direction in which water diffuses is dependent on its concentration within the cell compared
to outside the cell. Table 3.1 lists the cell organelles we have studied in the chapter. The nucleus
is a large organelle of primary importance because it controls the rest of the cell. Within the
nucleus lies the chromatin, which condenses to become chromosomes during cell division.
Proteins are made at the rough ER before being modified and packaged by the Golgi apparatus
into vesicles for secretion. During secretion, a vesicle discharges its contents at the plasma
membrane. Golgi-derived lysosomes fuse with incoming vesicles to digest any material enclosed
within, and lysosomes also carry out auto digestion of old parts of cells. Mitochondria are the
powerhouses of the cell. During the process of cellular respiration, mitochondria convert
carbohydrate energy to ATP energy. Microtubules and actin filaments make up the cytoskeleton,
which maintains the cell’s shape and permits movement of cell parts. Centrioles are a part of the
microtubule organizing center, which is associated with the formation of microtubules in general
and the spindle that appears during cell division. Centrioles also produce basal bodies that give
rise to cilia and flagella.
Cellular metabolism
Cellular metabolism is the sum of all biochemical pathways of the cell. In a pathway, a series
of reactions proceeds in an orderly step-by-step manner. Each of these reactions requires a
specific enzyme. Sometimes enzymes require coenzymes, nonprotein portions that participate in
the reaction. NAD is a coenzyme. Cellular respiration (the breakdown of glucose to carbon
dioxide and water) includes three pathways: glycolysis, the Krebs cycle, and the electron
transport system. If oxygen is not available in cells, the electron transport system is inoperative,
and fermentation (an anaerobic process) occurs. Fermentation makes use of glycolysis only, plus
one more reaction in which pyruvate is reduced to lactate.
