Organization of the Cell
Chapter 4
Learning Objective 1
•
What is cell theory?
•
How does cell theory relate to the
evolution of life?
Cell Theory
(1)
Cells are basic units of organization
and function in all living organisms
(2)
All cells come from other cells
All living cells have evolved from a
common ancestor
Learning Objective 2
•
What is the relationship between cell
organization and homeostasis?
Homeostasis
•
Cells have many organelles, internal
structures that carry out specific
functions, that help maintain
homeostasis
KEY CONCEPTS
•
Cell organization and size are critical in
maintaining homeostasis
Plasma Membrane
•
Plasma membrane
•
•
•
•
surrounds the cell
separates cell from external environment
maintains internal conditions
allows the cell to exchange materials with
outer environment
KEY CONCEPTS
•
Eukaryotic cells are divided into
compartments by internal membranes
•
Membranes provide separate, small
areas for specialized activities
Learning Objective 3
•
What is the relationship between cell
size and homeostasis?
Biological Size
Mitochondrion
Protein
Amino
Atom acids
0.1 nm 1 nm
Red blood
cells
Chloroplast Typical
bacteria
Human
egg
Chicken
egg
Virus
Nucleus
Ribosomes Smallest
bacteria
10 nm 100 nm
Epithelial
cell
1 μm
10 μm 100 μm
Frog egg
1 mm
Some
nerve cells
10 mm
100 mm
Adult
human
1m
10 m
Electron microscope
Light microscope
Human eye
Measurements
1 meter = 1000 millimeters (mm)
1 millimeter = 1000 micrometers (μm)
1 micrometer = 1000 nanometers (nm)
Fig. 4-1, p. 75
Surface to Volume Ratio
•
SVR
ratio of plasma membrane (surface area)
to cell’s volume
• regulates passage of materials into and out
of the cell
•
•
Critical factor in determining cell size
SVR
1 mm
2 mm
2 mm
Surface Area
(mm2)
Surface area =
height width
number of sides
number of cubes
Volume
(mm3)
Volume =
height width
length
number of cubes
Surface Area/
Volume Ratio
Surface area/
volume
24
(2 2 6 1)
8
(2 2 2 1)
3
(24 :8)
1 mm
48
(1 1 6 8)
8
(1 1 1 8)
6
(48 :8)
Fig. 4-2, p. 76
Learning Objective 4
•
What methods do biologists use to
study cells?
•
How are microscopy and cell
fractionation used?
Microscopes
•
Light microscopes
•
Electron microscopes
•
superior resolving power
Microscopes
Light
microscope
Light beam
Ocular lens
Objective lens
Specimen
Condenser lens
Light source
(a) A phase contrast
light microscope can be
used to view stained or
living cells, but at
relatively low resolution.
100 μm
Fig. 4-4a, p. 79
Transmission
electron
microscope
Electron gun
Electron beam
First condenser lens
(electromagnet)
Specimen
Projector lens
(electromagnetic)
Film or screen
(b) The transmission
electron microscope
(TEM) produces a highresolution image
that can be greatly
magnified. A small
part of a thin slice
through the
Paramecium is shown.
1 μm
Fig. 4-4b, p. 79
Electron gun
Electron beam
First condenser lens
(electromagnet)
Secondary
electrons
Scanning
electron
microscope
Second condenser
lens
Scanning coil
Final (objective)
lens
Cathode ray tube
synchronized with
scanning coil
Specimen
Electron
detector
(c) The scanning
electron microscope
(SEM) provides a clear
view of surface
features.
100 μm
Fig. 4-4c, p. 79
Cell Fractionation
•
Cell fractionation
•
•
purifies organelles
to study function of cell structures
Cell Fractionation
Centrifuge rotor
Centrifugal force
Centrifugal force
Hinged bucket
containing tube
(a) Centrifugation. Due to centrifugal force, large or very dense particles
move toward the bottom of a tube and form a pellet.
Fig. 4-5a, p. 80
Centrifuge
600 x G
10
minutes
Disrupt
cells in
buffered
solution
30
minutes
Nuclei in
pellet
Centrifuge
supernatant
100,000 x G
90
minutes
Low sucrose
concentration
Resuspend
pellet layer
on top of
sucrose
gradient
Mitochondria,
chloroplasts
Microsomal pellet
in pellet
(contains ER, Golgi,
plasma membrane)
Sucrose density
gradient
Centrifuge
supernatant
20,000 x G
Layered
microsomal
suspension
Plasma
membrane
Density
gradient
centrifugation
100,000 x G
High
Golgi
sucrose
concentration
ER
(b) Differential centrifugation. Cell structures can be separated into various fractions by spinning the
suspension at increasing revolutions per minute. Membranes and organelles from the re-suspended
pellets can then be further purified by density gradient centrifugation (shown as last step). G is the
force of gravity. ER is the endoplasmic reticulum.
Fig. 4-5b, p. 80
Layered
microsomal
suspension
Centrifuge
supernatant
100,000 x G
Centrifuge
600 x G
10
minutes
Disrupt
cells in
buffered
solution
Nuclei in
pellet
30
minutes
90
minutes
Plasma
membrane
Resuspend
pellet layer
on top of
sucrose
gradient
Mitochondria,
chloroplasts Microsomal pellet
(contains ER, Golgi,
in pellet
plasma membrane)
Sucrose density
gradient
Centrifuge
supernatant
20,000 x G
Low sucrose
concentration
Density
gradient
centrifugation
100,000 x G
Golgi
High sucrose
concentration
ER
Stepped Art
Fig. 4-5b, p. 80
Learning Objective 5
•
How do the general characteristics of
prokaryotic and eukaryotic cells differ?
•
How are plant and animal cells
different?
Prokaryotes
•
Prokaryotic cells
•
•
•
•
•
No internal membrane organization
nuclear area (not nucleus)
cell wall
ribosomes
flagella
Prokaryotes
Pili
Storage granule
Flagellum
Ribosome
Cell wall
DNA
Plasma
membrane
Nuclear
area
Capsule
0.5 μm
Fig. 4-6, p. 81
Eukaryotes
•
Eukaryotic cells
•
•
•
membrane-enclosed nucleus
cytoplasm contains organelles
cytosol (fluid component)
Animal Cells
Chromatin
Membranous
sacs of
Golgi
Nuclear
envelope
Nucleolus
Nuclear
pores
Nucleus
Golgi complex
Plasma
membrane
Lysosome
Nuclear
envelope
Cristae
Ribosomes
Rough
ER
Rough and smooth
endoplastic reticulum (ER)
Smooth ER
Centrioles
Mitochondrion
Fig. 4-8, p. 83
Plant Cells
•
Plant cells
•
•
•
•
rigid cell walls
plastids
large vacuoles
no centrioles
Plant Cells
Mitochondrion
Cristae
Membranous
sacs
Golgi complex
Cell wall
Plasma membrane
Vacuole
Chloroplast
Granum
Nucleus
Smooth ER
Nuclear envelope
Stroma
Nucleolus
Nuclear pores
Rough ER
Ribosomes
Chromatin
Rough and smooth
endoplasmic reticulum (ER)
Fig. 4-7, p. 82
Learning Objective 6
•
What are the three functions of cell
membranes?
Cell Membranes
•
Divide cell into compartments
•
Vesicles transport materials between
compartments
•
Important in energy storage and
conversion
•
Endomembrane system
Learning Objective 7
•
What are the structures and functions of
the nucleus?
The Nucleus
•
Control center of cell
•
•
Nuclear envelope
•
•
genetic information coded in DNA
double membrane
Nuclear pores
•
communicate with cytoplasm
Nuclear Structures
•
Chromatin
•
•
Chromosomes
•
•
DNA and protein
DNA condensed for cell division
Nucleolus
•
•
ribosomal RNA synthesis
ribosome assembly
The Nucleus
Rough ER
Nuclear
pores
Chromatin
Nucleolus
(b)
0.25 μm
Nuclear
envelope
Nuclear
pore
Nucleoplasm
ER continuous
with outer membrane
of nuclear envelope
Outer
nuclear
envelope Nuclear pore
2 μm
(a)
Nuclear
pore
(c) proteins
Inner nuclear
envelope
Fig. 4-11, p. 88
KEY CONCEPTS
•
Eukaryotic cells have nuclei containing
genetic information coded in DNA
Learning Objective 8
•
What are the structural and functional
differences between smooth ER and
rough ER?
Endoplasmic Reticulum (ER)
•
Network of folded membranes
•
•
Smooth ER
•
•
•
•
in cytosol
lipid synthesis
calcium ion storage
detoxifying enzymes
Rough ER
•
•
ribosomes on outer surface
assembles proteins
ER
ER lumen
Mitochondrion
Ribosomes
Rough
ER
1 μm
Smooth ER
Fig. 4-12, p. 90
Learning Objective 9
•
Trace the path of protein synthesis:
synthesis in the rough ER
processing, modification, and sorting by
the Golgi complex
• transportation to specific destinations
•
•
The Golgi Complex
•
Processes proteins synthesized by ER
•
Manufactures lysosomes
•
Cisternae
•
stacks of flattened membranous sacs
Transport Vesicles
•
Formed by membrane budding
•
Move glycoproteins
•
•
from ER to cis face of Golgi complex
Carry modified proteins from trans face to
specific destination
Protein Synthesis
Polypeptides synthesized
on ribosomes are inserted
into ER lumen.
Ribosomes
Sugars are added,
forming glycoproteins.
Rough ER
Transport vesicles
Glycoprotein
deliver glycoproteins
to cis face of Golgi.
Glycoproteins modified
further in Golgi.
Glycoproteins move to trans
face where they are packaged
in transport vesicles.
Glycoproteins transported to
plasma membrane (or other
organelle).
Contents of transport vesicle
released from cell.
Plasma
membrane
cis
face
trans
face
Golgi complex
Fig. 4-14, p. 92
KEY CONCEPTS
•
Proteins are
•
•
•
•
synthesized on ribosomes
processed in the endoplasmic reticulum
processed by the Golgi complex
transported by vesicles
Learning Objective 10
•
What are the functions of lysosomes,
vacuoles, and peroxisomes?
Other Organelles
•
Lysosomes
•
•
Vacuoles
•
•
enzymes break down structures
store materials in plant cells
Peroxisomes
•
produce and degrade hydrogen peroxide
(catalase)
Learning Objective 11
•
Compare the functions of mitochondria
and chloroplasts
•
How is ATP synthesized by each of
these organelles?
Mitochondria
•
Site of aerobic respiration
•
Double membrane
•
•
•
inner membrane folded (cristae)
matrix (cristae and inner compartment)
Important in apoptosis
•
programmed cell death
Mitochondria
Outer
mitochondrial Inner
mitochondrial
membrane
membrane
Matrix
Cristae
0.25 μm
Fig. 4-19, p. 95
Aerobic Respiration
•
Breaks down nutrients using oxygen
•
Energy from nutrients packaged in ATP
•
CO2, H2O produced as by-products
Plastids
•
Plastids
•
•
•
organelles that produce and store food
in cells of plants and algae
Chloroplasts
•
plastids that carry out photosynthesis
Chloroplast Structure
•
Stroma
•
•
fluid-filled space enclosed by inner
membrane of chloroplast
Grana
•
•
stacks of membranous sacs (thylakoids)
suspended in stroma
Chloroplasts
Outer
membrane
Inner
membrane
Stroma
1 μm
Intermembrane Thylakoid
space
membrane
Thylakoid
lumen
Granum
(stack of
thylakoids)
Fig. 4-20, p. 96
Photosynthesis
•
Chlorophyll
•
•
•
green pigment in thylakoid membranes
traps light energy
Light energy converted to chemical
energy in ATP
•
used to synthesize carbohydrates from
carbon dioxide and water
Mitochondria and
Chloroplasts
Aerobic respiration
Mitochondria (most eukaryotic cells)
Glucose
Photosynthesis
Chloroplasts (some plant and
algal cells)
Light
Glucose
Fig. 4-18, p. 95
KEY CONCEPTS
•
Mitochondria and chloroplasts convert
energy from one form to another
Learning Objective 12
•
What are the structures and functions of
the cytoskeleton?
The Cytoskeleton
•
Microtubules
•
•
•
Microfilaments
•
•
•
hollow tubulin cylinders
MTOCs and MAPs
actin filaments
important in cell movement
Intermediate filaments
•
•
strengthen cytoskeleton
stabilize cell shape
Microtubules
α-Tubulin
Dimer on
Plus end
β-Tubulin
Minus end
Dimers
off
(a) Microtubules are manufactured in the cell by adding dimers of α-tubulin
and β-tubulin to an end of the hollow cylinder. Notice that the cylinder has
polarity. The end shown at the top of the figure is the fast-growing, or plus,
end; the opposite end is the minus end. Each turn of the spiral requires 13
dimers.
Fig. 4-22a, p. 98
Intermediate Filaments
Protofilament
Protein subunits
Intermediate filament
(a) Intermediate filaments are flexible rods about
10 nm in diameter. Each intermediate filament
consists of components, called protofilaments,
composed of coiled protein subunits.
Fig. 4-27a, p. 101
100 μm
(b) Intermediate filaments are stained green in
this human cell isolated from a tissue culture.
Fig. 4-27b, p. 101
Microfilaments
(a) A microfilament consists of two intertwined strings of beadlike
actin molecules.
Fig. 4-26a, p. 101
100 μm
(b) Many bundles of microfilaments (green) are evident in this
fluorescent LM of fibroblasts, cells found in connective tissue.
Fig. 4-26b, p. 101
Cytoskeleton
Plasma
membrane
Microfilament
Intermediate
filament
Microtubule
Fig. 4-21, p. 97
Centrosome
•
Main MTOC of animal cells
•
Usually contains two centrioles
•
Each centriole has 9 x 3 arrangement of
microtubules
Centrioles
MTOC
Centrioles
0.25 μm
(a) In the TEM, the centrioles are positioned at
right angles to each other, near the nucleus of
a nondividing animal cell.
Fig. 4-24a, p. 99
(b) Note the 9 x 3 arrangement of microtubules.
The centriole on the right has been cut transversely.
Fig. 4-24b, p. 99
A Kinesin Motor
Vesicle
Kinesin
receptor
Kinesin
ATP
ATP
Minus
end
Plus
end
Microtubule does not move
Fig. 4-23, p. 98
KEY CONCEPTS
•
The cytoskeleton is a dynamic internal
framework that functions in various
types of cell movement
Learning Objective 13
•
How do cilia and flagella differ in
structure and function?
Cilia and Flagella
•
Cilia and flagella
•
•
•
•
thin, movable structures
project from cell surface
function in movement
Cilia are short, flagella are long
Cilia
0.5 μm
(a) TEM of a longitudinal section through
cilia and basal bodies of the freshwater
protist Paramecium multimicronucleatum.
Some of the interior microtubules are
visible.
Fig. 4-25a, p. 100
0.5 μm
(b) TEM of cross sections
through cilia showing
9 + 2 arrangement of
microtubules.
Fig. 4-25b, p. 100
0.5 μm
(c) TEM of cross section
through basal body
showing 9 x 3 structure.
Fig. 4-25c, p. 100
Outer pair of microtubules
Dynein
Plasma membrane
Central microtubules
(d) This 3-D representation shows
nine attached microtubule pairs
(doublets) arranged in a cylinder,
with two unattached microtubules
in the center. The dynein “arms,”
shown widely spaced for clarity,
are actually much closer together
along the longitudinal axis.
Fig. 4-25d, p. 100
(e) The dynein arms move the
microtubules by forming and
breaking cross bridges on the
adjacent microtubules, so that
one microtubule “walks” along
its neighbor. Flexible linking
proteins between microtubule
pairs prevent microtubules from
sliding very far. Instead, the
motor action causes the
microtubules to bend, resulting
in a beating motion.
Microtubular
bend
Linking
proteins
Dynein
Pair of
microtubules
Fig. 4-25e, p. 100
Learning Objective14
•
Describe the glycocalyx, extracellular
matrix, and cell wall
Cell Coat
•
Glycocalyx (cell coat)
•
•
Surrounds cell
Polysaccharides extend from plasma
membrane
ECM
•
Extracellular matrix (ECM)
•
•
•
Fibronectins
•
•
•
Surrounds many animal cell
Carbohydrates and protein
glycoproteins of ECM
bind to integrins
Integrins
•
receptor proteins in plasma membrane
ECM
Collagen
Fibronectins
Extracellular
matrix
Integrin
Intermediate
filament
Microfilaments
Plasma
membrane
Cytosol
Fig. 4-28, p. 102
Cell Wall
•
Cellulose & other polysaccharides
•
•
form rigid cell walls
in bacteria, fungi, and plant cells
Cell 1
Middle
lamella
Primary cell wall
Multiple layers of
secondary cell wall
Cell 2
2.5 μm
Fig. 4-29, p. 102
Typical Prokaryotic Cell
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Plant Cell Walls
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Cytoskeletal Components
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Common Eukaryotic
Organelles
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Flagella Structure
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Motor Proteins
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The Endomembrane System
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