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Cell Architecture
“Of the things of nature there are … two kinds:
those which are brought into being and perish, and those which are
free from these processes throughout all ages. The latter are of the highest
worth and are divine…
Aristotle 384-322 BC from Parts of Animals
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-2
10 m
Human height
Length of some
nerve and
muscle cells
0.1 m
Chicken egg
1 cm
Unaided eye
1m
Frog egg
100 µm
Most plant and
animal cells
10 µm
Nucleus
Most bacteria
1 µm
PowerPoint Lectures for
Biology, Seventh Edition
Mitochondrion
Smallest bacteria
100 nm
Neil Campbell and Jane Reece
Viruses
Ribosomes
10 nm
Proteins
Lipids
1 nm
Small molecules
Lectures by Chris Romero
0.1 nm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Atoms
Electron microscope
Measurements
1 centimeter (cm) = 10–2 meter (m) = 0.4 inch
1 millimeter (mm) = 10–3 m
1 micrometer (µm) = 10–3 mm = 10–6 m
1 nanometer (nm) = 10–3 µm = 10–9 m
Light microscope
1 mm
LE 6a
Forms of Light Microscopy
Brightfield
50 µm
Brightfield
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Phase-contrast
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-3b
Differential-interference-contrast (DIC)
(Nomarski)
Fluorescence
50 µm
Confocal
PowerPoint Lectures for
Biology, Seventh Edition
(laser beam)
Neil Campbell and Jane Reece
Lectures by Chris Romero
Conventional fluorescence
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-4
Cilia
Scanning electron
microscopy (SEM)
1 µm
Surface of rabbit tracheal cells
Transmission electron
microscopy (TEM)
Longitudinal
section of
cilium
PowerPoint Lectures for
Section
of tracheal
Biology,
Seventh
Edition tissue
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cross section
of cilium
1 µm
Surface area increases while
Total volume remains constant
LE 6-7
5
1
1
Total surface area
(height x width x
number of sides x
number of boxes)
6
150
750
Total volume
(height x width x length
PowerPoint
Lectures for
X number of boxes)
1
125
125
6
1.2
6
Biology, Seventh Edition
Neil Campbell and Jane Reece
Surface-to-volume
ratio
(surface by
area
 volume)
Lectures
Chris
Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Isolating Organelles by Cell Fractionation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-5a
Homogenization
Tissue
cells
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Differential centrifugation
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Homogenate
LE 6-5b
1000 g
(1000 times the
force of gravity)
10 min
Supernatant poured
into next tube
20,000 g
20 min
80,000 g
60 min
Pellet rich in
nuclei and
cellular debris
150,000 g
3 hr
Pellet rich in
mitochondria
(and chloroplasts if cells
are from a plant)
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Pellet rich in
“microsomes”
(pieces of plasma
membranes and
cells’ internal
membranes)
Pellet rich in
ribosomes
Cells Exhibit Evolutionary Relatedness
by their Similarities & Differences
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-6
Pili
Nucleoid
Ribosomes
Plasma
membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 µm
Flagella
Prokaryote
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
A typical
rod-shaped
bacterium
Lectures
by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
A thin section through the
bacterium Bacillus
coagulans (TEM)
ENDOPLASMIC RETICULUM (ER
LE 6-9a
Nuclear envelope
Flagellum
Rough ER
Smooth ER
Nucleolus
NUCLEUS
Chromatin
Centrosome
Plasma membrane
CYTOSKELETON
Microfilaments
Intermediate filaments
Microtubules
Ribosomes:
Microvilli
PowerPoint Lectures for
Biology, Seventh Edition
Golgi apparatus
Peroxisome
Neil Campbell and Jane Reece
Mitochondrion
Non-plant
cell
Lectures
by Chriseukaryotic
Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Lysosome
In animal cells but not plant cells: Lysosomes
Centrioles
Flagella (in some plant sperm)
Nuclear
envelope
LE 6-9b
NUCLEUS
Nucleolus
Rough
endoplasmic
reticulum
Chromatin
Smooth
endoplasmic
reticulum
Centrosome
Ribosomes
(small brown dots)
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
CYTOSKELETON
Mitochondrion
Peroxisome
Chloroplast
Plasma
PowerPointmembrane
Lectures
for
Biology, SeventhCellEdition
wall
Neil Campbell and Jane Reece
Plasmodesmata
Wall of adjacent cell
Plant
cellRomero
Lectures
by Chris
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In plant cells but not animal cells: Chloroplasts
Central vacuole and tonoplast
Cell wall
Plasmodesmata
• Basic features of ALL cells:
– Plasma membrane
– Semifluid substance called the cytosol
– Chromosomes (carry genes)
– Ribosomes (make proteins)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-8
Plasma membrane
Outside of cell
Carbohydrate side chain
Hydrophilic
region
Inside of cell
0.1 µm
Hydrophobic
region
PowerPoint Lectures for
Biology, Seventh Edition
Hydrophilic
Neil Campbell and Jane Reece
region
TEM of aby
plasma
Lectures
Chrismembrane
Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Phospholipid
Proteins
Structure of the plasma membrane
LE 6-10
Nucleus
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Rough ER
Surface of nuclear envelope
PowerPoint Lectures for
0.25
µm
Biology,
Seventh Edition
Ribosome
Neil Campbell and Jane Reece
1 µm
Close-up of nuclear
envelope
Lectures by Chris Romero
Pore complexes (TEM)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nuclear lamina (TEM)
LE 6-12
Smooth ER
Nuclear
envelope
Rough ER
ER lumen
Cisternae
Ribosomes
Transitional ER
Transport vesicle
Smooth ER
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Rough ER
200 nm
Functions of Smooth ER
• The smooth ER
– Synthesizes lipids
– Metabolizes carbohydrates
– Stores calcium
– Detoxifies poison
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Functions of Rough ER
• The rough ER
– Has bound ribosomes that make proteins
targeted for membranes or to be transported
across membranes
– Is a membrane factory for the cell
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-11
Ribosomes
ER
Cytosol
Endoplasmic
reticulum (ER)
Free ribosomes
Bound ribosomes
Large
subunit
PowerPoint Lectures for
Biology, Seventh Edition
Small
subunit
0.5 µm
Neil Campbell and Jane Reece
TEM showing ER
Lectures by Chris Romeroand ribosomes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Ribosome
LE 6-13
Golgi Apparatus
Golgi
apparatus
cis face
(“receiving” side of
Golgi apparatus)
Vesicles also
transport certain
proteins back to ER
Vesicles move
from ER to Golgi
Vesicles coalesce to
form new cis Golgi cisternae
0.1 µm
Cisternae
Cisternal
maturation:
Golgi cisternae
move in a cisto-trans
direction
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Vesicles transport specific
proteins backward to newer
Golgi cisternae
Lectures by Chris Romero
Vesicles form and
leave Golgi, carrying
specific proteins to
other locations or to
the plasma membrane for secretion
trans face
(“shipping” side of
Golgi apparatus)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
TEM of Golgi apparatus
The Endomembrane System: A Review
• The endomembrane system is a complex and
dynamic player in the cell’s compartmental
organization
Animation: Endomembrane System
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Lysosomes: Digestive Compartments
• Membranous sacs of hydrolytic enzymes
• Hydrolyze (breaks down) proteins, fats,
polysaccharides, and nucleic acids
• Recycle organelles and macromolecules
(autophagy)
• Hydrolyze food taken up by the cell (phagocytosis)
Animation: Lysosome Formation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Lysosomes: Digestive Compartments
• Formation of lysosomes with hydrolytic enzyme
Animation: Lysosome Formation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-14a
1 µm
Nucleus
Lysosome
Lysosome contains
active hydrolytic
enzymes
Food vacuole
fuses with
lysosome
Hydrolytic
enzymes digest
food particles
Digestive
enzymes
Plasma
membrane
PowerPoint Lectures
for
Lysosome
Biology, Seventh Edition
Neil Campbell and Jane Reece
Food vacuole
Lectures by Chris Romero
Phagocytosis: lysosome digesting food
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Digestion
Lysosome containing
two damaged organelles
LE 6-14b
1 µm
Mitochondrion
fragment
Peroxisome
fragment
Hydrolytic enzymes
digest organelle
components
Lysosome fuses with
vesicle containing
damaged organelle
Lysosome
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Digestion
Vesicle containing
damaged mitochondrion
Autophagy:
Lectures
by Chrislysosome
Romerobreaking down
damaged organelle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vacuoles: Diverse Maintenance Compartments
• Vesicles and vacuoles (larger versions of vesicles)
are membrane-bound sacs with varied functions
• A plant cell or fungal cell may have one or several
vacuoles
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Food vacuoles: form by phagocytosis
• Contractile vacuoles: pump excess water out of
cells (in many freshwater protists)
• Central vacuoles (plant cells): hold organic
compounds and water, maintain turgor pressure
Video: Paramecium Vacuole
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-15
Central vacuole
Cytosol
Tonoplast
Nucleus
Central
vacuole
PowerPoint Lectures for
Biology, Seventh Edition
Cell wall
Neil Campbell and Jane Reece
Chloroplast
Lectures by Chris Romero
5 µm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 6.5: Mitochondria and chloroplasts
change energy from one form to another
• Mitochondria are the sites of cellular respiration
• Chloroplasts, found only in plants and algae, are
the sites of photosynthesis
• Mitochondria and chloroplasts are not part of the
endomembrane system
• Peroxisomes are oxidative organelles
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mitochondria: Chemical Energy Conversion
• Mitochondria are in nearly all eukaryotic cells
• They have a smooth outer membrane and an
inner membrane folded into cristae
• The inner membrane creates two compartments:
intermembrane space and mitochondrial matrix
• Some metabolic steps of cellular respiration are
catalyzed in the mitochondrial matrix
• Cristae present a large surface area for enzymes
that synthesize ATP
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-17
Mitochondrion
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Inner
membrane
Cristae
Matrix
Mitochondrial
Lectures
by Chris Romero
DNA
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
100 nm
Chloroplasts: Capture of Light Energy
• The chloroplast is a member of a family of
organelles called plastids
• Chloroplasts contain the green pigment
chlorophyll, as well as enzymes and other
molecules that function in photosynthesis
• Chloroplasts are found in leaves and other green
organs of plants and in algae
• Chloroplast structure includes:
– Thylakoids, membranous sacs
– Stroma, the internal fluid
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-18
Chloroplast
Ribosomes
Stroma
Chloroplast
DNA
Inner and outer
membranes
PowerPoint Lectures for
Biology, Seventh Edition
Granum
Neil Campbell and Jane Reece
Thylakoid
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1 µm
Peroxisomes: Oxidation
• Peroxisomes are specialized metabolic
compartments bounded by a single membrane
• Peroxisomes produce hydrogen peroxide and
convert it to water
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-19
Chloroplast
Peroxisome
Mitochondrion
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
1 µm
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Summary
-Microscopy and differential centrifugation are two powerful
methods to examine cellular structure and function.
-Optimal size for most cells is generally low to optimize
surface area:volume ratio.
-All cells have plasma membrane, cytosol, DNA and ribosomes.
-Prokaryotic cells tend to be smaller than eukaryotic,
and lack nuclei, cytoplasmic membranes
systems and organelles.
PowerPoint Lectures for
Biology, Seventh Edition
-Eukaryotic
have
Neil Campbellcells
and Jane
Reece evolved or acquired many membrane
bound compartments for specialized functions.
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Please,
ask questions.
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Eukaryotic Cell Structure: Part II
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Cytoskeleton
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Dynamic: shorten and lengthen
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-27b
Cortex (outer cytoplasm):
gel with actin network
Inner cytoplasm: sol
with actin subunits
Extending
pseudopodium
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Amoeboid movement
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-26
Microvillus
Intestinal cell
Plasma membrane
Microfilaments
(actin filaments)
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Intermediate filaments
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
0.25 µm
LE 6-27a
Muscle cell
Actin filament
Myosin filament
Myosin arm
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Myosin motors in muscle cell contraction
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-27c
Nonmoving
cytoplasm (gel)
Chloroplast
Streaming
cytoplasm
(sol)
Vacuole
Parallel actin
filaments
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Cytoplasmic streaming in plant cells
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cell wall
Dynamic: shorten and lengthen
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-21b
Microtubule
Vesicles
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
0.25 µm
LE 6-21a
Vesicle
ATP
Receptor for
motor protein
PowerPoint Lectures
for
Motor
Biology, Seventh Edition
protein
(ATP powered)
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Microtubule
of cytoskeleton
LE 6-23a
Motile sperm
Direction of swimming
flagellum
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Motion of flagella
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
5 µm
LE 6-23b
Direction of organism’s movement
Direction of
active stroke
Direction of
recovery stroke
Motion of
cilia for
PowerPoint
Lectures
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
protozoan
15 µm
Microtubules Power Flagella & Cilia
Movement
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-25a
Microtubule
doublets
ATPATP
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Dynein arm
Molecular motor
Dynein “walking”
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cross-linking
LE
6-25b
proteins inside
outer doublets
ATP
Anchorage
in cell
Effect of cross-linking proteins
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Wavelike motion
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-24
MT organization in Flagella and Cilia
0.1 µm
Outer microtubule
doublet
Dynein arms
Central
microtubule
Cross-linking
proteins inside
outer doublets
Microtubules
Plasma
membrane
Basal body
9+2
0.5 µm
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Radial
spoke
Plasma
membrane
Basal body
Microtubule-containing structure at base of flagellum
and cilium
Organization: Nine triplets
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-24
Basal body anchors each flagellum and cilium
9 doublets+2
Plasma
membrane
Basal body
0.5 µm
Basal Body
Triplet
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Cross section of basal body
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nine triplets
Centrioles
• Occur in pairs oriented at right angle
• Similar nine triplet organization as basal body
• Present in animal cells
• Contained in centrosome:microtubule organizing
center (MTOC)
• Note: plants cells have centrosomes but lack
centrioles
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-22
Centrosome
Microtubule
Centrioles
0.25 µm
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures
by Chris Romero
Longitudinal section
of one centriole
Microtubules
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cross section
of the other centriole
Concept 6.7: Extracellular components and connections
between cells help coordinate cellular activities
• Most cells synthesize and secrete materials that
are external to the plasma membrane
• These extracellular structures include:
–
Cell walls of plants
– The extracellular matrix (ECM) of animal cells
– Intercellular junctions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cell Walls of Plants
• extracellular structure that distinguishes plant cells
from animal cells
• protects the plant cell, maintains its shape, and
prevents excessive uptake of water
• made of cellulose fibers embedded in other
polysaccharides and protein
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cell Walls of Plants
• may have multiple layers:
– Primary cell wall: relatively thin and flexible
– Middle lamella: thin layer between primary
walls of adjacent cells
– Secondary cell wall (in some cells): added
between the plasma membrane and the
primary cell wall
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-28
Central
vacuole
of cell
Plasma
membrane
Secondary
cell wall
Primary
cell wall
Central
vacuole
of cell
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
PowerPoint Lectures for
Biology, Seventh Edition
Plant cell walls
Neil Campbell and Jane Reece
Lectures by Chris Romero
Plasmodesmata
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Plasmodesmata are channels between adjacent plant cells
channels that perforate plant cell walls
water and small solutes (and sometimes proteins and RNA)
can pass from cell to cell
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-30
Cell walls
Interior
of cell
Interior
of cell
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
0.5 µm
Plasmodesmata
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Plasma membranes
The Extracellular Matrix (ECM) of Animal Cells
• Animal cells lack cell walls but are covered by an
elaborate extracellular matrix (ECM)
• The ECM is made up of glycoproteins and other
macromolecules
• Functions of the ECM:
– Support
– Adhesion
– Movement
– Regulation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-29a
Collagen
fiber
EXTRACELLULAR FLUID
Fibronectin
Plasma
membrane
PowerPoint Lectures for
Biology, Seventh Edition
Integrin
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
CYTOPLASM
Microfilaments
Proteoglycan
complex
LE 6-29b
Proteoglycan
complex
Polysaccharide
molecule
Carbohydrates
Core
protein
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Proteoglycan
molecule
Intercellular Junctions
• Neighboring cells in tissues, organs, or organ
systems often adhere, interact, and communicate
through direct physical contact
• Three types of intercellular junctions facilitate this
contact
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Animals: Tight Junctions, Desmosomes, and Gap Junctions
• Tight junctions
–
membranes of neighboring cells are pressed together,
preventing leakage of extracellular fluid
• Desmosomes (anchoring junctions)
–
fasten cells together into strong sheets
• Gap junctions (communicating junctions)
–
provide cytoplasmic channels between adjacent cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-31
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
1 µm
Space
between
cells for
Lectures
Gap
junctions
PowerPoint
Biology, Seventh Edition
Plasma membranes
NeilofCampbell
and Jane Reece
adjacent cells
Gap junction
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Extracellular
matrix
0.1 µm
The Cell: A Living Unit Greater Than the Sum of Its Parts
• Cells rely on the integration of structures and
organelles in order to function
• For example, a macrophage’s ability to destroy
bacteria involves the whole cell, coordinating
components such as the cytoskeleton, lysosomes,
and plasma membrane
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
5 µm
LE 6-32
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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