ASSIGMENT DISCUSSION
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Mader_Essentials_7e_LecturePPT_Ch04_ACCESS.pptxChapter 4
Inside the Cell
Essentials of Biology
SEVENTH EDITION
Sylvia S. Mader Michael Windelspecht
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4.1 Cells Under the Microscope
Cells
Are extremely diverse
Each type in our body is specialized for a particular function.
Nearly, all require a microscope to be seen.
Light microscope
Invented in the seventeenth century
Limited by properties of light
Electron microscope
Invented in 1930s
Overcomes limitation by using beam of electrons
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Figure 4.1 Using Microscopes to See Cells
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(using TEM): The Center for Electron Microscopy and Analysis (CEMAS) at The Ohio State University/McGraw Hill; (epithelial cell): Dr. Kath White, photographer/EM Research Services, Newcastle University/McGraw Hill; (pluripotent stem cell): Steve Gschmeissner/Alamy Stock Photo; (using light microscope): Fuse/Corbis/Getty Images; (Euglena): Richard Gross/McGraw Hill
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Figure 4.2 Relative Sizes of Some Living Things and Their Components
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The Limit to Cell Size
Why are cells so small?
Need surface areas large enough for entry and exit of materials
Surface-area-to-volume ratio
Small cells have more surface area for exchange.
Adaptations to increase surface area
Microvilli in the small intestine increase surface area for absorption of nutrients
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Figure 4.3 Surface-Area-to-Volume Relationships
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4.2 The Plasma Membrane
Marks boundary between outside and inside of a cell
Regulates passage in and out of a cell
Phospholipid bilayer with embedded proteins
Polar heads (hydrophilic) of phospholipids face into watery medium
Nonpolar tails (hydrophobic) face each other
Fluid mosaic model—the structure of the plasma membrane
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Figure 4.4 A Model of the Plasma Membrane
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Figure 4.5a Membrane Protein Diversity—Channel Protein
Membrane proteins
Channel proteins
Form tunnel for specific molecules
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Figure 4.5b Membrane Protein Diversity—Transport Protein
Transport proteins
Involved in passage of molecules through the membrane, sometimes requiring input of energy
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Figure 4.5c Membrane Protein Diversity—Cell Recognition Protein
Cell recognition proteins
Enable our body to distinguish between our own cells and cells of other organisms
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Figure 4.5d Membrane Protein Diversity—Receptor Protein
Receptor proteins
Allow signal molecules to bind, causing a cellular response
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Figure 4.5e Membrane Protein Diversity—Enzymatic Proteins
Enzymatic proteins
Directly participate in metabolic reactions
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Figure 4.5f Membrane Protein Diversity—Junction Proteins
Junction proteins
Form junctions between cells
Cell-to-cell adhesion and communication
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4.3 The Two Main Types of Cells
Cell theory
All organisms are composed of cells.
All cells come only from preexisting cells.
All cells have:
A plasma membrane to regulate movement of material
Cytoplasm where chemical reactions occur
Genetic material for growth and reproduction
Two main types of cells
Based on organization of genetic material
Prokaryotic cells—lack membrane-bounded nucleus
Eukaryotic cells—have nucleus housing DNA
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Prokaryotic Cells
Prokaryotic cells
Organisms from the domains Bacteria and Archaea
Generally smaller and simpler in structure than eukaryotic cells
Allows them to reproduce very quickly and effectively
Extremely successful group of organisms
Bacteria
Well known because some cause disease
Others have roles in the environment
Some are used to manufacture chemicals, food, drugs, and so on.
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Bacterial Structure
Bacterial structure:
Cytoplasm surrounded by plasma membrane and cell wall
Sometimes a capsule—protective layer
Plasma membrane is the same as eukaryotes
Cell wall maintains the shape of a cell
DNA—single circular, coiled chromosome located in nucleoid (region—not membrane enclosed)
Ribosomes—site of protein synthesis
Appendages
Flagella—propulsion
Fimbriae—attachment to surfaces
Conjugation pili—DNA transfer
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Figure 4.6 A Prokaryotic Cell
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4.4 A Tour of the Eukaryotic Cell
Protists, fungi, plants, and animals
Have a membrane-bounded nucleus housing DNA
Much larger than prokaryotic cells
Compartmentalized and contain organelles
Four categories of organelles:
Nucleus and ribosomes
Endomembrane system
Energy-related
Cytoskeleton
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Figure 4.7 Structure of a Typical Animal Cell
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Figure 4.8a Structure of a Typical Plant Cell
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Figure 4.8b Structure of a Typical Plant Cell
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Nucleus and Ribosomes
Nucleus and ribosomes:
Nucleus
Stores genetic information
Chromatin—diffuse DNA, protein, some RNA
Prior to cell division, DNA compacts into chromosomes
DNA organized into genes, which specify a polypeptide
Relayed to ribosome using messenger RNA (mRNA)
Nucleolus—region where ribosomal RNA (rRNA) is made
Nuclear envelope—double membrane
Nuclear pores permit passage in and out
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Figure 4.9 Structure of the Nucleus
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Ribosomes
Ribosomes
Carry out protein synthesis in the cytoplasm
Found in both prokaryotes and eukaryotes
Composed of two subunits
Mix of proteins and rRNA
Receive mRNA as instructions sequence of amino acids in a polypeptide
In eukaryotes:
Some ribosomes free in cytoplasm
Many attached to endoplasmic reticulum
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Figure 4.10 The Nucleus, Ribosomes, and Endoplasmic Reticulum (ER)
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Endomembrane System 1
Endomembrane system:
Consists of nuclear envelope, membranes of endoplasmic reticulum, Golgi apparatus, and numerous vesicles
Helps compartmentalize cell
Restricts certain reactions to specific regions
Transport vesicles carry molecules from one part of the system to another.
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Endoplasmic Reticulum
Endoplasmic reticulum:
Complicated system of membranous channels and saccules
Physically continuous with outer membrane of nuclear envelope
Rough ER
Studded with ribosomes
Modifies proteins in lumen
Forms transport vesicles going to Golgi apparatus
Smooth ER
Continuous with rough ER
No ribosomes
Synthesizes lipids like phospholipids and steroids
Function depends on cell
Produces testosterone, detoxifies drugs
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Figure 4.11 Endoplasmic Reticulum (ER)
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Figure 4.12 Endomembrane System
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Endomembrane System 2
Golgi apparatus
Stack of flattened saccules
Transfer station
Receives vesicles from ER
Modifies molecules within the vesicles
Sorts and repackages for new destination
Some are lysosomes.
Lysosomes
Vesicles that digest molecules or portions of the cell
Digestive enzymes
Tay-Sachs disease
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Vacuoles
Vacuoles:
Membranous sacs
Larger than vesicles
Rid a cell of excess water
Digestion
Storage
Plant pigments
Animal adipocytes
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Figure 4.13 Vacuoles
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(a): micro_photo/iStock/Getty Images; (b): Biophoto Associates/Science Source
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Energy-Related Organelles
Energy-related organelles:
Mitochondria
Found in both plants and animals
Usually only visible under an electron microscope
Bounded by double membrane
Break down carbohydrates to produce adenosine triphosphate (ATP)
Cellular respiration—needs oxygen, produces carbon dioxide.
Inner membrane folds called cristae
Increase surface area
Inner membrane encloses matrix
Mixture of enzymes assisting in carbohydrate breakdown
Reactions permit ATP synthesis.
Matrix also contains its own DNA and ribosomes.
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Chloroplasts
Chloroplasts:
Use solar energy to synthesize carbohydrates through the process of photosynthesis
Plants and algae
Three-membrane system
Double membrane enclosing stroma
Thylakoids formed from third membrane.
Thylakoid membrane contains pigments that capture solar energy
Chloroplasts have their own DNA and ribosomes.
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Figure 4.14a Chloroplast Structure
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Figure 4.14b Electron Micrograph of a Chloroplast
(b): Omikron/Science Source
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Figure 4.15 Mitochondrion Structure
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The Cytoskeleton and Motor Proteins 1
The cytoskeleton and motor proteins:
Cytoskeleton—network of interconnected protein filaments and tubules
Extends from the nucleus to the plasma membrane
Only in eukaryotes
Maintains cell shape
Motor proteins—allow cell and organelles to move
Myosin, kinesin, and dynein
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The Cytoskeleton and Motor Proteins 2
Motor proteins:
Instrumental in allowing cellular movements
Myosin
Interacts with actin
Cells move in amoeboid fashion
Muscle contraction
Kinesin and dynein
Move along microtubules
Transport vesicles from Golgi apparatus to final destination
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Figure 4.16a Motor Proteins
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Figure 4.16b Motor Proteins
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The Cytoskeleton and Motor Proteins—Microtubules and Intermediate Filaments
Microtubules
Small, hollow cylinders
Assembly controlled by centrosome
Help maintain cell shape and act as track for organelles and other materials to move
Intermediate filaments
Intermediate in size
Ropelike assembly
Run from nuclear envelope to plasma membrane
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Figure 4.17 Microtubules
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Figure 4.18 Actin Filaments
Actin filaments:
Two chains of monomers twisted in a helix
Forms a dense web to support the cell
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The Cytoskeleton and Motor Proteins—Centrioles
Centrioles:
Made of nine sets of microtubule triplets
Two centrioles lie at right angles
In animal cells; not present in plant cells
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Figure 4.19 Centrioles
(photo): Don W. Fawcett/Science Source
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Cilia and Flagella
Cilia and flagella:
Eukaryotes
For movement of the cell or fluids past the cell
Similar construction in both
9+2 pattern of microtubules
Cilia shorter and more numerous than flagella
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Figure 4.20 Cilia and Flagella
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(a): (cilia): Cultura Creative Ltd/Alamy Stock Photo; (flagella of sperm): David M. Phillips/Science Source; (b): (flagellum cross section): Steve Gschmeissner/Science Source
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4.5 Outside the Eukaryotic Cell
Plant cell walls
Primary cell walls
Cellulose fibrils and noncellulose substances
Wall stretches when cell is growing
Secondary cell walls (some plant cells)
Forms inside primary cell wall
Woody plants
Lignin adds strength
Plasmodesmata
Plant cells connected by numerous channels that pass through cell walls
For exchange of water and small solutes between cells
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Figure 4.21 Animal Cell Extracellular Matrix
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Exterior Cell Surfaces in Animals
Exterior cell surfaces in animals:
No cell wall
Extracellular matrix (ECM)
Meshwork of fibrous proteins and polysaccharides
Collagen and elastin—well-known proteins
Matrix varies—flexible in cartilage, hard in bone
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Cell Wall
Cell wall provides support to cell in many nonanimal cells
plant
fungi
protists
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Extracellular Matrix
The extracellular matrix, found in animal cells, is a meshwork of fibrous proteins and polypeptides in close association with the cell that produced them.
Collagen—resists stretching
Elastin—provides resilience
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Figure 4.22 Junctions Between Cells of the Intestinal Wall
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Adhesion Junctions
Junctions between cells
Adhesion junctions
Internal cytoplasmic plaques joined by intercellular filaments
Sturdy but flexible sheet of cells
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Tight Junctions
Junctions between cells
Tight junctions
Impermeable barrier
Adjacent plasma membraned joined
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Gap Junctions
Junctions between cells
Gap junctions
Allow communication between two cells
Adjacent plasma membrane channels joined
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Figure 4.1 Using Microscopes to See Cells - Text Alternative
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The first photo shows a scientist using an electron microscope. The second photo shows a transmission electron micrograph (TEM) of a cell showing its numerous organelles. The third photo shows a scanning electron micrograph (SEM) of a stem cell at 4,000 times magnification. The stem cell has two types of projections, small and circular, and numerous finger-like projections. The fourth photo shows a scientist using a light microscope. The fifth photo shows a light microscopic view of a Euglena at 470 times magnification. Euglena is an elongated cell with a red eyespot and many organelles.
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Figure 4.2 Relative Sizes of Some Living Things and Their Components - Text Alternative
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The scale shows the following: atoms: 0.1 nm, amino acids: 1 nm, proteins: 10 nm, viruses: 100 nm, chloroplast: 1 μm, most bacteria: 10 μm, plant and animal cells: 100 μm, human egg: more than 100 μm. Frog egg: 1 mm, ant: 1 cm, mouse: 0.1 m, man: 1 m, blue whale: 10 m. Organisms below 100 μm are categorized under electron microscope, organisms between 100 nm and 1 mm are under light microscope, organisms between 100 μm and 1 km are categorized under unaided eye.
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Figure 4.4 A Model of the Plasma Membrane - Text Alternative
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A magnified image of the plasma membrane of a cell shows a thick phospholipid bilayer. It consists of a polar head which is hydrophilic and nonpolar tails which are hydrophobic. Protein molecule, cholesterol, and glycol proteins are embedded in the bilayer. A carbohydrate chain is attached to the glycol protein. Cytoskeleton membranes emerge from the bottom. The upper surface is labeled external membrane surface and the lower surface is labeled internal membrane surface.
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Figure 4.6 A Prokaryotic Cell - Text Alternative
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The cylindrical cross-sectional diagram of a prokaryotic cell shows the labels and their descriptions as follows:
Capsule: Gel-like coating outside the cell wall.
Nucleoid: Location of the bacterial chromosome.
Ribosome: Site of protein synthesis.
Plasma membrane: Sheet that surrounds the cytoplasm and regulates entrance and exit of molecules.
Cell wall: Structure that provides support and shapes the cell.
Cytoplasm: Semifluid solution surrounded by the plasma membrane; contains nucleoid and ribosomes.
Flagellum: Rotating filament that propels the cell.
The micrograph of Escherichia coli shares the same top six labels of the diagram of the prokaryotic cell, other than the flagellum.
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Figure 4.7 Structure of a Typical Animal Cell - Text Alternative
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a. The micrograph shows five different cellular components including mitochondrion, nucleus, chromatin, peroxisome, and endoplasmic reticulum.
b. The cross-section of an animal cell shows 19 parts, labeled clockwise from bottom left as follows, Golgi apparatus, plasma membrane, cytoplasm, lysosome, smooth ER (Endoplasmic Reticulum), ribosome (attached to rough ER), mitochondrion, rough ER (Endoplasmic Reticulum), centrioles (in centrosome), vesicle, vesicle formation, nuclear envelope, nuclear pore, nucleolus, chromatin, filaments, microtubules, polyribosome (in cytoplasm), and ribosome (in cytoplasm). The nuclear envelope, nuclear pore, chromatin, and nucleolus are parts of the nucleus while filaments and microtubules are parts of the cytoskeleton.
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Figure 4.8a Structure of a Typical Plant Cell - Text Alternative
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It has the following parts labeled: chloroplast, cell wall, plasma membrane, nucleus, ribosomes, mitochondrion, peroxisome, and central vacuole.
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Figure 4.8b Structure of a Typical Plant Cell - Text Alternative
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It has the following parts labeled: cell wall, plasma membrane, cytoplasm, cell wall of adjacent cell, plasmodesmata, cytoskeleton: microtubule filaments, endomembrane system: rough ER, smooth ER, lysosome, Golgi apparatus, vesicle, energy organelles: chloroplast, mitochondrion, nucleus: ribosome (attached to rough ER), nuclear pore, chromatin, nucleolus, nuclear envelope, centrosome, central vacuole, ribosome in cytoplasm.
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Figure 4.9 Structure of the Nucleus - Text Alternative
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The cross-sectional diagram of an animal cell points to the enlarged view of the nucleus. The enlarged view of the nucleus shows eight labeled parts as follows: nuclear envelope consisting of outer membrane and inner membrane, nucleolus, chromatin, nucleoplasm, ER (Endoplasmic Reticulum) lumen, ribosome, endoplasmic reticulum, and nuclear pores.
The micrograph at 30,000 times magnification shows nuclear envelope containing numerous nuclear pores.
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Figure 4.10 The Nucleus, Ribosomes, and Endoplasmic Reticulum (ER) - Text Alternative
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The steps are as follows:
1) mRNA is produced in the nucleus but moves through a nuclear pore into the cytoplasm.
2) In the cytoplasm, the mRNA and ribosomal subunits join, and polypeptide synthesis begins.
3) If a ribosome attaches to a receptor on the ER, the polypeptide enters the lumen of the ER.
4) At termination, the polypeptide becomes a protein. The ribosomal subunits disengage, and the mRNA is released.
The labels include DNA, mRNA, and nuclear pore in the nucleus; cytoplasm; large unit; small subunit; polypeptide; ribosome; receptor; lumen of the ER; and ER membrane.
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Figure 4.11 Endoplasmic Reticulum (ER) - Text Alternative
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The cross-sectional diagram of the animal cell points to the enlarged view of the endoplasmic reticulum, which is attached to the nuclear envelope. Rough ER with ribosomes on its surface and smooth ER without ribosomes are also labeled. The micrograph shows the smooth ER and rough ER.
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Figure 4.12 Endomembrane System - Text Alternative
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Rough ER: synthesizes proteins and packages them in vesicles, transport vesicles contain products coming from ER. Golgi apparatus modifies lipids and proteins; sorts them and packages them in vesicles. Secretory vesicles fuse with the plasma membrane as secretion occurs. Smooth ER: synthesizes lipids and performs other functions. Transport vesicles contain products coming from ER. Lysosomes digest molecules or old cell parts. Incoming vesicles bring substances into the cell.
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Figure 4.13 Vacuoles - Text Alternative
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The micrograph of a plant cell labeled B, shows a roughly oval-shaped mitochondrion, nucleus, peroxisome adhered to the circumference, spots of ribosomes across the surface, an irregularly circular and large central vacuole, plasma membrane, external circumference of cell wall, and chloroplast.
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Figure 4.14a Chloroplast Structure - Text Alternative
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The cross-sectional diagram of a plant cell points to the enlarged diagram of the chloroplast labeled a. The enlarged diagram shows an oval-shaped structure covered with a double membrane: an outer membrane and an inner membrane. There are two distinct regions found inside the chloroplast called the granum and stroma. The space inside the inner membrane is filled with the homogenous matrix labeled stroma. A granum is made up of tight stacks of disc-shaped structures labeled thylakoids. The cut section of the thylakoid shows thylakoid space and thylakoid membrane.
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Figure 4.15 Mitochondrion Structure - Text Alternative
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The capsule shaped mitochondrion has the following parts labeled: outer membrane, inner membrane, matrix, and cristae.
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Figure 4.20 Cilia and Flagella - Text Alternative
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The micrographs and the diagram are as follows:
a. The micrograph shows hair-like cilia in the bronchial wall of lungs. Another micrograph of the sperm cell shows flagella of sperm attached to the oval heads.
b. The diagram shows a three-dimensional view of the structure of the flagella with five labels as follows: thin, tail-like flagellum, central microtubules, microtubule pairs, motor proteins, and plasma membrane of a cell. The TEM micrograph at 20,000 times magnification shows the cross-section of a flagellum with three joint labels, central microtubules, microtubule pairs, and motor proteins.
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Figure 4.21 Animal Cell Extracellular Matrix - Text Alternative
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It consists of an elastic fiber, collagen, polysaccharide, receptor protein, plasma membrane, cytoskeleton filament, and cytoplasm.
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Figure 4.22 Junctions Between Cells of the Intestinal Wall - Text Alternative
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A, Adhesion junction: The diagram shows the adhesion junction which forms a bridge between the plasma membranes of two adjacent cells. The parts labeled are intercellular space, filaments of cytoskeleton, plasma membranes, and intercellular filaments.
B, Tight junction: The diagram shows the tight junction which forms a protein that seals the plasma membranes of two adjacent cells. The parts labeled are intercellular space, tight junction proteins, and plasma membranes.
C, Gap junction: The diagram shows the gap junction which forms gap channels that link the plasma membranes of two adjacent cells. The parts labeled are plasma membranes, membrane channel, and intercellular space.
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Adhesion Junctions - Text Alternative
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Adhesion junction forms a bridge between the plasma membranes of two adjacent cells. The parts labeled are plasma membranes, filaments of cytoskeleton, intercellular filaments, and intercellular space.
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Tight Junctions - Text Alternative
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Tight junction forms proteins that seal the plasma membranes of two adjacent cells. The parts labeled are plasma membranes, tight junction proteins, and intercellular space.
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Gap Junctions - Text Alternative
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Gap junction forms gap channels that link the plasma membranes of two adjacent cells. The parts labeled are plasma membranes, membrane channel, and intercellular space.
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