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Chapter 4
A Tour of the Cell
PowerPoint Lectures
Campbell Biology: Concepts & Connections, Eighth Edition
REECE •TAYLOR • SIMON•DICKEY• HOGAN
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Lecture by Edward J. Zalisko
INTRODUCTION TO THE CELL
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4.3 Prokaryotic cells are structurally simpler
than eukaryotic cells
• Bacteria and archaea are prokaryotic cells.
• All other forms of life are composed of eukaryotic
cells.
• Eukaryotic cells are distinguished by having
• a membrane-enclosed nucleus and
• many membrane-enclosed organelles that perform
specific functions.
• Prokaryotic cells are smaller and simpler in
structure.
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4.3 Prokaryotic cells are structurally simpler
than eukaryotic cells
• Prokaryotic and eukaryotic cells have
• a plasma membrane,
• an interior filled with a thick, jellylike fluid called the
cytosol,
• one or more chromosomes, which carry genes
made of DNA, and
• ribosomes, tiny structures that make proteins
according to instructions from the genes.
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4.3 Prokaryotic cells are structurally simpler
than eukaryotic cells
• The inside of both types of cells is called the
cytoplasm.
• However, in eukaryotic cells, this term refers only
to the region between the nucleus and the plasma
membrane.
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4.3 Prokaryotic cells are structurally simpler
than eukaryotic cells
• In a prokaryotic cell,
• the DNA is coiled into a region called the nucleoid
(nucleus-like) and
• no membrane surrounds the DNA.
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4.3 Prokaryotic cells are structurally simpler
than eukaryotic cells
• Outside the plasma membrane of most prokaryotes
is a fairly rigid, chemically complex cell wall, which
• protects the cell and
• helps maintain its shape.
• Some prokaryotes have surface projections.
• Short projections help attach prokaryotes to each
other or their substrate.
• Longer projections called flagella (singular,
flagellum) propel a prokaryotic cell through its liquid
environment.
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Figure 4.3-0
Fimbriae
Ribosomes
Nucleoid
Plasma
membrane
Cell wall
Bacterial
chromosome
A typical rod-shaped
bacterium
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Capsule
A colorized TEM of the
bacterium Escherichia coli
Flagella
4.4 Eukaryotic cells are partitioned into
functional compartments
• A eukaryotic cell contains
• a membrane-enclosed nucleus and
• various other organelles (“little organs”), which
perform specific functions in the cell.
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4.4 Eukaryotic cells are partitioned into
functional compartments
• The structures and organelles of eukaryotic cells
perform four basic functions.
1. The nucleus and ribosomes are involved in the
genetic control of the cell.
2. The endoplasmic reticulum, Golgi apparatus,
lysosomes, vacuoles, and peroxisomes are
involved in the manufacture, distribution, and
breakdown of molecules.
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4.4 Eukaryotic cells are partitioned into
functional compartments
3. Mitochondria in all cells and chloroplasts in plant
cells are involved in energy processing.
4. Structural support, movement, and
communication between cells are functions of
the cytoskeleton, plasma membrane, and cell
wall.
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4.4 Eukaryotic cells are partitioned into
functional compartments
• The internal membranes of eukaryotic cells
partition it into compartments.
• Cellular metabolism, the many chemical activities
of cells, occurs within organelles.
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4.4 Eukaryotic cells are partitioned into
functional compartments
• Almost all of the organelles and other structures of
animals cells are present in plant cells.
• A few exceptions exist.
• Lysosomes and centrosomes containing centrioles
are not found in plant cells.
• Only the sperm cells of a few plant species have
flagella.
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4.4 Eukaryotic cells are partitioned into
functional compartments
• Plant but not animal cells have
• a rigid cell wall that contains cellulose,
• plasmodesmata, cytoplasmic channels through cell
walls that connect adjacent cells,
• chloroplasts, where photosynthesis occurs, and
• a central vacuole, a compartment that stores water
and a variety of chemicals.
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Figure 4.4a
Rough
endoplasmic
reticulum
NUCLEUS
Nuclear envelope
Nucleolus
Chromatin
Ribosomes
CYTOSKELETON
Microtubule
Microfilament
Intermediate
filament
Peroxisome
Smooth
endoplasmic
reticulum
Plasma
membrane
Golgi apparatus
Lysosome
Mitochondrion
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Centrosome
with pair of
centrioles
Figure 4.4b
Smooth
endoplasmic
reticulum
NUCLEUS
Nuclear envelope
Nucleolus
Chromatin
Rough
endoplasmic
reticulum
Mitochondrion
CYTOSKELETON
Microfilament
Microtubule
Central
vacuole
Ribosomes
Chloroplast
Cell wall
Plasmodesma
Cell wall of
adjacent cell
Golgi
apparatus
Peroxisome
Plasma
membrane
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THE NUCLEUS AND RIBOSOMES
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4.5 The nucleus contains the cell’s genetic
instructions
• The nucleus
• contains most of the cell’s DNA and
• controls the cell’s activities by directing protein
synthesis by making messenger RNA (mRNA).
• DNA is associated with many proteins and is
organized into structures called chromosomes.
• When a cell is not dividing, this complex of proteins
and DNA, called chromatin, appears as a diffuse
mass within the nucleus.
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4.5 The nucleus contains the cell’s genetic
instructions
• The double membrane nuclearenvelope has
pores that
• regulate the entry and exit of large molecules and
• connect with the cell’s network of membranes
called the endoplasmic reticulum.
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4.5 The nucleus contains the cell’s genetic
instructions
• The nucleolus is
• a prominent structure in the nucleus and
• the site of ribosomal RNA (rRNA) synthesis.
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Figure 4.5
Nuclear
envelope
Endoplasmic
reticulum
Ribosome
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Nucleolus
Pore
Chromatin
4.6 Ribosomes make proteins for use in the
cell and export
• Ribosomes are involved in the cell’s protein
synthesis.
• Ribosomes are the cellular components that use
instructions from the nucleus, written in mRNA, to
build proteins.
• Cells that make a lot of proteins have a large
number of ribosomes.
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4.6 Ribosomes make proteins for use in the
cell and export
• Some ribosomes are free ribosomes; others are
bound.
• Free ribosomes are suspended in the cytosol.
• Bound ribosomes are attached to the outside of the
endoplasmic reticulum or nuclear envelope.
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Figure 4.6
Rough ER
Bound ribosome
Endoplasmic
reticulum
Protein
Ribosome
Free ribosome
mRNA
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THE ENDOMEMBRANE SYSTEM
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4.7 Many organelles are connected in the
endomembrane system
• Many of the membranes within a eukaryotic cell
are part of the endomembrane system.
• Some of these membranes are physically
connected, and others are linked when tiny
vesicles (sacs made of membrane) transfer
membrane segments between them.
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4.7 Many organelles are connected in the
endomembrane system
• Many of these organelles interact in the
•
•
•
•
synthesis,
distribution,
storage, and
export of molecules.
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4.7 Many organelles are connected in the
endomembrane system
• The endomembrane system includes the
•
•
•
•
•
•
nuclear envelope,
endoplasmic reticulum (ER),
Golgi apparatus,
lysosomes,
vacuoles, and
plasma membrane.
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4.7 Many organelles are connected in the
endomembrane system
• The largest component of the endomembrane
system is the endoplasmic reticulum (ER), an
extensive network of flattened sacs and tubules.
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4.8 The endoplasmic reticulum is a
biosynthetic workshop
• There are two kinds of endoplasmic reticulum,
which differ in structure and function.
1. SmoothER lacks attached ribosomes.
2. RoughERhas bound ribosomes that stud the
outer surface of the membrane.
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Figure 4.8a
Rough ER
Smooth ER
Ribosomes
Rough ER
Smooth ER
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Figure 4.8b
Transport vesicle
buds off
4
Secretory
protein
inside transport vesicle
mRNA
Bound ribosome
3
Sugar
chain
1
2
Growing
polypeptide
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Glycoprotein
Rough ER
4.8 The endoplasmic reticulum is a
biosynthetic workshop
• Smooth ER is involved in a variety of metabolic
processes, including
• the production of enzymes important in the
synthesis of lipids, oils, phospholipids, and steroids,
• the production of enzymes that help process drugs,
alcohol, and other potentially harmful substances,
and
• the storage of calcium ions.
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4.8 The endoplasmic reticulum is a
biosynthetic workshop
• Rough ER makes
• additional membrane for itself and
• secretory proteins.
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4.9 The Golgi apparatus modifies, sorts, and
ships cell products
• The Golgi apparatus serves as a molecular
warehouse and processing station for products
manufactured by the ER.
• Products travel in transport vesicles from the ER to
the Golgi apparatus.
• One side of the Golgi stack serves as a receiving
dock for transport vesicles produced by the ER.
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4.9 The Golgi apparatus modifies, sorts, and
ships cell products
• Products of the ER are modified as a Golgi sac
progresses through the stack.
• The “shipping” side of the Golgi functions as a
depot, where products in vesicles bud off and travel
to other sites.
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2015
Pearson
Education,
Inc.
2012
Pearson
Education,
Inc.
Figure 4.9
“Receiving” side of Golgi apparatus
Transport vesicle
from the ER
1
2
3
Golgi apparatus
4
Transport
vesicle from
the Golgi
“Shipping” side of
Golgi apparatus
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4.10 Lysosomes are digestive compartments
within a cell
• A lysosome is a membrane-enclosed sac of
digestive enzymes
• made by rough ER and
• processed in the Golgi apparatus
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4.10 Lysosomes are digestive compartments
within a cell
• Lysosomes
• fuse with food vacuoles and digest food,
• destroy bacteria engulfed by white blood cells, or
• fuse with other vesicles containing damaged
organelles or other materials to be recycled within a
cell.
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Figure 4.10b-3
Lysosome
Digestion
Vesicle containing
damaged mitochondrion
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4.11 Vacuoles function in the general
maintenance of the cell
• Vacuoles are large vesicles that have a variety of
functions.
• Some protists have contractile vacuoles, which help
to eliminate water from the protist.
• In plants, vacuoles may
• have digestive functions,
• contain pigments, or
• contain poisons that protect the plant.
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Figure 4.11a
Contractile
vacuoles
Nucleus
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Figure 4.11b
Central vacuole
Chloroplast
Nucleus
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4.12 A review of the structures involved in
manufacturing and breakdown
• The following figure summarizes the relationships
among the major organelles of the endomembrane
system.
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Figure 4.12
Nucleus
Smooth ER
Nuclear envelope
Rough ER
Golgi apparatus
Transport vesicle
Plasma
membrane
Lysosome
Transport
vesicle
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4.12 A review of the structures involved in
manufacturing and breakdown
• Peroxisomes are metabolic compartments that do
not originate from the endomembrane system.
• How they are related to other organelles is still
unknown.
• Some peroxisomes break down fatty acids to be
used as cellular fuel.
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ENERGY-CONVERTING
ORGANELLES
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4.13 Mitochondria harvest chemical energy
from food
• Mitochondria are organelles that carry out cellular
respiration in nearly all eukaryotic cells.
• Cellular respiration converts the chemical energy
in foods to chemical energy in ATP (adenosine
triphosphate).
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4.13 Mitochondria harvest chemical energy
from food
• Mitochondria have two internal compartments.
1. The intermembrane space is the narrow region
between the inner and outer membranes.
2. The mitochondrialmatrix contains
• the mitochondrial DNA,
• ribosomes, and
• many enzymes that catalyze some of the reactions
of cellular respiration.
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4.13 Mitochondria harvest chemical energy
from food
• Folds of the inner mitochondrial membrane, called
cristae, increase the membrane’s surface area,
enhancing the mitochondrion’s ability to produce
ATP.
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Figure 4.13
Mitochondrion
Intermembrane
space
Outer
membrane
Inner
membrane
Crista
Matrix
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4.14 Chloroplasts convert solar energy to
chemical energy
• Photosynthesis is the conversion of light energy
from the sun to the chemical energy of sugar
molecules.
• Chloroplasts are the photosynthesizing
organelles of plants and algae.
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4.14 Chloroplasts convert solar energy to
chemical energy
• Chloroplasts are partitioned into compartments.
• Between the outer and inner membrane is a thin
intermembrane space.
• Inside the inner membrane is a thick fluid called
stroma, which contains the chloroplast DNA,
ribosomes, many enzymes, and a network of
interconnected sacs called thylakoids, where green
chlorophyll molecules trap solar energy.
• In some regions, thylakoids are stacked like poker
chips. Each stack is called a granum.
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Figure 4.14
Chloroplast
Granum
Stroma
Inner and
outer membranes
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Thylakoid
4.15 EVOLUTION CONNECTION:
Mitochondria and chloroplasts evolved by
endosymbiosis
• Mitochondria and chloroplasts contain
• DNA and
• ribosomes.
• The structure of this DNA and these ribosomes is
very similar to that found in prokaryotic cells.
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4.15 EVOLUTION CONNECTION:
Mitochondria and chloroplasts evolved by
endosymbiosis
• The endosymbionttheory states that
• mitochondria and chloroplasts were formerly small
prokaryotes and
• they began living within larger cells.
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Figure 4.15
Endoplasmic
reticulum
Nucleus
Engulfing of oxygenusing prokaryote
Ancestor of
eukaryotic cells (host cell)
Mitochondrion
Engulfing of
photosynthetic
prokaryote
Mitochondrion
At least
one cell
Nonphotosynthetic
eukaryote
Chloroplast
Photosynthetic eukaryote
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THE CYTOSKELETON AND
CELL SURFACES
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4.16 The cell’s internal skeleton helps
organize its structure and activities
• Cells contain a network of protein fibers, called the
cytoskeleton, which organize the structures and
activities of the cell.
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4.16 The cell’s internal skeleton helps
organize its structure and activities
• Microtubules (made of tubulin)
• shape and support the cell and
• act as tracks along which organelles equipped with
motor proteins move.
• In animal cells, microtubules grow out from a
region near the nucleus called the centrosome,
which contains a pair of centrioles, each composed
of a ring of microtubules.
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4.16 The cell’s internal skeleton helps
organize its structure and activities
• Intermediatefilaments
• are found in the cells of most animals,
• reinforce cell shape and anchor some organelles,
and
• are often more permanent fixtures in the cell.
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4.16 The cell’s internal skeleton helps
organize its structure and activities
• Microfilaments (actin filaments)
• support the cell’s shape and
• are involved in motility.
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Figure 4.16-0
Nucleus
Nucleus
10 nm
7 nm
25 nm
Intermediate filament
Microtubule
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Microfilament
4.17 SCIENTIFIC THINKING: Scientists
discovered the cytoskeleton using the tools
of biochemistry and microscopy
• In the 1940s, biochemists first isolated and
identified the proteins actin and myosin from
muscle cells.
• In 1954, scientists, using newly developed
techniques of microscopy, established how
filaments of actin and myosin interact in muscle
contraction.
• In the next decade, researchers identified actin
filaments in all types of cells.
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4.17 SCIENTIFIC THINKING: Scientists
discovered the cytoskeleton using the tools
of biochemistry and microscopy
• In the 1970s, scientists were able to visualize actin
filaments using fluorescent tags and in living cells.
• In the 1980s, biologists were able to record the
changing architecture of the cytoskeleton.
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Figure 4.17
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4.18 Cilia and flagella move when
microtubules bend
• The short, numerous appendages that propel
protists such as Paramecium are called cilia
(singular, cilium).
• Other protists may move using flagella, which are
longer than cilia and usually limited to one or a few
per cell.
• Some cells of multicellular organisms also have
cilia or flagella.
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Figure 4.18b
Flagellum
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4.18 Cilia and flagella move when
microtubules bend
• A flagellum, longer than cilia, propels a cell by an
undulating, whiplike motion.
• Cilia work more like the oars of a boat.
• Although differences exist, flagella and cilia have a
common structure and mechanism of movement.
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4.18 Cilia and flagella move when
microtubules bend
• Both flagella and cilia are composed of
microtubules wrapped in an extension of the
plasma membrane.
• In nearly all eukaryotic cilia and flagella, a ring of
nine microtubule doublets surrounds a central pair
of microtubules.
• This arrangement is called the 9  2 pattern.
• The microtubule assembly is anchored in a basal
body with nine microtubule triplets arranged in a
ring.
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Figure 4.18c-0
Outer
microtubule
doublet
Central
microtubules
Cross-linking
proteins
Motor proteins
(dyneins)
Plasma membrane
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4.18 Cilia and flagella move when
microtubules bend
• Cilia and flagella move by bending motor proteins
called dynein feet.
• These feet attach to and exert a sliding force on an
adjacent doublet.
• This “walking” causes the microtubules to bend.
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4.19 The extracellular matrix of animal cells
functions in support and regulation
• Animal cells synthesize and secrete an elaborate
extracellularmatrix (ECM), which
• helps hold cells together in tissues and
• protects and supports the plasma membrane.
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4.19 The extracellular matrix of animal cells
functions in support and regulation
• The ECM may attach to the cell through other
glycoproteins that then bind to membrane proteins
called integrins.
• Integrins
• span the membrane and
• attach on the other side to proteins connected to
microfilaments of the cytoskeleton.
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Figure 4.19
Glycoprotein
complex with long
polysaccharide
EXTRACELLULAR FLUID
Collagen fiber
Connecting
glycoprotein
Integrin
Plasma
membrane
CYTOPLASM
Microfilaments
of cytoskeleton
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4.20 Three types of cell junctions are found in
animal tissues
• Adjacent cells adhere, interact, and communicate
through specialized junctions between them.
• Tight junctions prevent leakage of fluid across a
layer of epithelial cells.
• Anchoring junctions fasten cells together into
sheets.
• Gap junctions are channels that allow small
molecules to flow through protein-lined pores
between cells.
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Figure 4.20
Tight junctions
prevent fluid from
moving across a
layer of cells
Tight junction
Anchoring
junction
Gap junction
Plasma membranes
of adjacent cells
Ions or small molecules
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Extracellular matrix
4.21 Cell walls enclose and support plant
cells
• A plant cell, but not an animal cell, has a rigid
cellwall that
• protects and provides skeletal support that helps
keep the plant upright and
• is primarily composed of cellulose.
• Plant cells have cell junctions called
plasmodesmata that allow plants tissues to share
• water,
• nourishment, and
• chemical messages.
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Figure 4.21
Plant cell
walls
Vacuole
Plasmodesmata
Primary cell wall
Secondary cell wall
Plasma membrane
Cytosol
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4.22 Review: Eukaryotic cell structures can
be grouped on the basis of four main
functions
• Eukaryotic cell structures can be grouped on the
basis of four functions:
1. genetic control,
2. manufacturing, distribution, and breakdown of
materials,
3. energy processing, and
4. structural support, movement, and intercellular
communication.
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Table 4-22-0
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