Organic Molecules and their Importance in Living Things
mattymatt121
Mason_UB3e_ch03_PPT_final_Accessible.pptxChapter 3 Lecture Outline
Understanding Biology
THIRD EDITION
Kenneth A. Mason
Tod Duncan
Jonathan B. Losos
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The Chemical Building Blocks of Life
Chapter 3
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Carbon
Framework of biological molecules consists primarily of carbon bonded to
Carbon
O, N, S, P or H
Can form up to 4 covalent bonds
Hydrocarbons – molecule consisting only of carbon and hydrogen
Nonpolar
Functional groups add chemical properties
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3
Figure 3.1
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Isomers
Molecules with the same molecular or empirical formula
Structural isomers
Stereoisomers – differ in how groups attached
Enantiomers
mirror image molecules
chiral
D-sugars and L-amino acids
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Figure 3.2
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Macromolecules 1
Four general classes
Carbohydrates
Lipids
Proteins
Nucleic acids
Polymer – built by linking monomers
Monomer – small, similar chemical subunits
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Macromolecules 2
TABLE 3.1 Macromolecules
| Macromolecule | Subunit | Function | Example |
| CARBOHYDRATES | |||
| Starch, glycogen | Glucose | Energy storage | Potatoes |
| Cellulose | Glucose | Structural support in plant cell walls | Paper; strings of celery |
| Chitin | Modified glucose | Structural support | Crab shells |
| PROTEINS | |||
| Functional | Amino acids | Catalysis; transport | Hemoglobin |
| Structural | Amino acids | Support | Hair; silk |
| NUCLEIC ACIDS | |||
| DNA | Nucleotides | Encodes genes | Chromosomes |
| RNA | Nucleotides | Needed for gene expression | Messenger RNA |
| LIPIDS | |||
| Fats | Glycerol and three fatty acids | Energy storage | Butter; corn oil; soap |
| Phospholipids | Glycerol, two fatty acids, phosphate, and polar R groups | Cell membranes | Phosphatidylcholine |
| Prostaglandins | Five-carbon rings with two nonpolar tails | Chemical messengers | Prostaglandin E (PGE) |
| Steroids | Four fused carbon rings | Membranes; hormones | Cholesterol; estrogen |
| Terpenes | Long carbon chains | Pigments; structural support | Carotene; rubber |
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Figure 3.3
Dehydration synthesis
Formation of large molecules by the removal of water
Monomers are joined to form polymers
Hydrolysis
Breakdown of large molecules by the addition of water
Polymers are broken down to monomers
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Carbohydrates
Molecules with a 1:2:1 ratio of carbon, hydrogen, oxygen
Empirical formula (CH2O)n
C—H covalent bonds hold much energy
Carbohydrates are good energy storage molecules
Examples: sugars, starch, glucose
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Monosaccharides
Simplest carbohydrate
6 carbon sugars play important roles
Glucose C6H12O6
Fructose is a structural isomer of glucose
Galactose is a stereoisomer of glucose
Enzymes that act on different sugars can distinguish structural and stereoisomers of this basic six-carbon skeleton
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Figure 3.4
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Figure 3.5
Structure of the glucose molecule.
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Figure 3.6
Structural isomers and stereoisomers.
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Disaccharides
Two monosaccharides linked together by dehydration synthesis
Used for sugar transport or energy storage
Examples: sucrose, lactose, maltose
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Polysaccharides
Long chains of monosaccharides
Linked through dehydration synthesis
Energy storage
Plants use starch
Animals use glycogen
Structural support
Plants use cellulose
Arthropods and fungi use chitin
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Figure 3.8
Access the text alternative for slide images.
(b): ©Asa Thoresen/Science Source; (c): ©J.L. Carson/CMSP Biology/Newscom
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Figure 3.9
(b): ©Asa Thoresen/Science Source; (c): ©J.L. Carson/CMSP Biology/Newscom
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Proteins
Protein functions include:
Enzyme catalysis
Defense
Transport
Support
Motion
Regulation
Storage
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Amino acids
Proteins are polymers
Composed of 1 or more long, unbranched chains
Each chain is a polypeptide
Amino acids are monomers
Amino acid structure
Central carbon atom
Amino group
Carboxyl group
Single hydrogen
Variable R group
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R Groups
R groups determine the chemistry of the amino acid:
Nonpolar - leucine
Polar uncharged - threonine
Charged - glutamic acid
Aromatic - phenylalanine
Unique – proline and cysteine
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Figure 3.12
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Figure 3.11
Amino acids joined by dehydration synthesis
Peptide bond
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Protein structure (primary and secondary)
The shape of a protein determines its function
Primary structure – sequence of amino acids
Secondary structure – interaction of groups in the peptide backbone
α helix
β sheet
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Protein structure (tertiary and quaternary)
Tertiary structure – final folded shape of a globular protein
Stabilized by a number of forces
Final level of structure for proteins consisting of only a single polypeptide chain
Quaternary structure – arrangement of individual chains (subunits) in a protein with two or more polypeptide chains
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Figure 3.13
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Additional structural characteristics
Motifs
Common elements of secondary structure seen in many polypeptides
Useful in determining the function of unknown proteins
Domains
Functional units within a larger structure
Most proteins made of multiple domains that perform different parts of the protein’s function
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Figure 3.16
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Chaperones
Once thought newly made proteins folded spontaneously
Chaperone proteins help protein fold correctly
Deficiencies in chaperone proteins implicated in certain diseases
Cystic fibrosis is a hereditary disorder
In some individuals, protein appears to have correct amino acid sequence but fails to fold
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Figure 3.17
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Denaturation
Protein loses structure and function
Due to environmental conditions
pH
Temperature
Ionic concentration of solution
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Nucleic acids
Polymer – nucleic acids
Monomers – nucleotides
sugar + phosphate + nitrogenous base
sugar is deoxyribose in DNA or ribose in RNA
Nitrogenous bases include
Purines: adenine and guanine
Pyrimidines: thymine, cytosine, uracil
Nucleotides connected by phosphodiester bonds
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Figure 3.21
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Figure 3.22
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Figure 3.20
DNA versus RNA
DNA forms a double helix, uses deoxyribose, and uses thymine among its nitrogenous bases.
RNA is usually single-stranded, uses ribose, and uses uracil in place of thymine.
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Deoxyribonucleic acid (DNA)
Encodes information for amino acid sequence of proteins
Sequence of bases
Double helix – 2 polynucleotide strands connected by hydrogen bonds
Base-pairing rules
A with T (or U in RNA)
C with G
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Figure 3.23
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Ribonucleic acid (RNA)
RNA similar to DNA except
Contains ribose instead of deoxyribose
Contains uracil instead of thymine
Single polynucleotide strand
RNA uses information in DNA to specify sequence of amino acids in proteins
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Other nucleotides
ATP adenosine triphosphate
Primary energy currency of the cell
NAD+ and FAD+
Electron carriers for many cellular reactions
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Lipids
Hydrophobic lipids form fats and membranes
Loosely defined group of molecules with one main chemical characteristic
They are insoluble in water
High proportion of nonpolar C—H bonds causes the molecule to be hydrophobic
Fats, oils, waxes, and even some vitamins
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Fats
Triglycerides
Composed of 1 glycerol and 3 fatty acids
Fatty acids
Need not be identical
Chain length varies
Saturated – no double bonds between carbon atoms
Higher melting point, animal origin
Unsaturated – 1 or more double bonds
Low melting point, plant origin
Trans fats produced industrially
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Figure 3.25
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Phospholipids
Composed of
Glycerol
2 fatty acids – nonpolar “tails”
A phosphate group – polar “head”
Form all biological membranes
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Figure 3.27
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Figure 3.28a
Micelles – lipid molecules orient with polar (hydrophilic) head toward water and nonpolar (hydrophobic) tails away from water
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Figure 3.28b
Phospholipid bilayer – more complicated structure where 2 layers form
Hydrophilic heads point outward
Hydrophobic tails point inward toward each other
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Figure 3.26
Other kinds of lipids
a. Terpenes are found in biological pigments, such as chlorophyll and retinal, and b. steroids play important roles in membranes and as hormones involved in chemical signaling.
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Accessibility Content: Text Alternatives for Images
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Figure 3.1 - Text Alternative
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Examples include hydroxyl, carbonyl, carboxyl, amino, sulfhydryl, phosphate, and methyl.
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Figure 3.2 - Text Alternative
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Left and right hands at the bottom of the picture and two mirror image chiral molecules at the top of the picture showing that the molecules have the same atoms, but arranged differently.
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Figure 3.3 - Text Alternative
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In a hydrolysis reaction water is used to break a larger molecule into two smaller molecules.
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Figure 3.5 - Text Alternative
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In the ring form if the hydroxyl group on carbon 1 is pointing up it is alpha-glucose but if it is pointing down it is beta-glucose.
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Figure 3.6 - Text Alternative
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Fructose is a structural isomer of glucose with a C=O in different locations. Glucose and galactose are steroisomers with an OH group on opposite sides of the sugar.
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Disaccharides - Text Alternative
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Maltose is a disaccharide of two glucose attached to each other.
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Figure 3.8 - Text Alternative
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These molecules vary in the amount of branching, from no branching to highly branched.
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Figure 3.13 - Text Alternative
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These molecules vary in the amount of branching, from no branching to highly branched.
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Figure 3.17 - Text Alternative
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The denatured protein is engulfed inside of the chaperone and ATP is used to provide energy to help the protein fold properly before being released from the chaperone.
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Figure 3.22 - Text Alternative
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The attached nitrogenous bases are either purines with two rings or pyrimidines with a single ring.
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Figure 3.20 - Text Alternative
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RNA is single stranded with the bases projecting out from the ribose-phosphate backbone.
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Other nucleotides - Text Alternative
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It consists of a ribose attached to three phosphates at its 5 prime carbon and a nitrogenous base at its 1 prime carbon.
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Figure 3.25 - Text Alternative
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Saturated fats do not have double bonds in the fatty acid tails and are straight and tightly packed, making them more solid. Unsaturated fats have double bonds within the fatty acid tails which make them bend and not pack as tightly so they are more fluid.
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Figure 3.28a - Text Alternative
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A micelle forms when the hydrophilic head groups of phospholipids point outward towards water and the hydrophobic tails point inward, forming a round lipid droplet.
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Figure 3.28b - Text Alternative
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A lipid bilayer forms when two rows of phospholipids are arranged with their hydrophilic head groups pointing outward towards water and the hydrophobic tails pointing inward towards those on the other row of phospholipids. This forms two layers of phospholipids.
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