Download Plant Cell - Wesleyan College Faculty

Chapter 6
A Tour of the 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
(d) Differential-interference-contrast (Nomarski).
Like phase-contrast microscopy, it uses optical
modifications to exaggerate differences in
density, making the image appear almost 3D.
(e) Fluorescence. Shows the locations of specific
molecules in the cell by tagging the molecules
with fluorescent dyes or antibodies. These
fluorescent substances absorb ultraviolet
radiation and emit visible light, as shown
here in a cell from an artery.
50 µm
(f) Confocal. Uses lasers and special optics for
“optical sectioning” of fluorescently-stained
specimens. Only a single plane of focus is
illuminated; out-of-focus fluorescence above
and below the plane is subtracted by a computer.
A sharp image results, as seen in stained nervous
tissue (top), where nerve cells are green, support
cells are red, and regions of overlap are yellow. A
standard fluorescence micrograph (bottom) of this
relatively thick tissue is blurry.
50 µm
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Figure 6.3 Research Method Light Microscopy
TECHNIQUE
RESULTS
(a) Brightfield (unstained specimen).
Passes light directly through specimen.
Unless cell is naturally pigmented or
artificially stained, image has little
contrast. [Parts (a)–(d) show a
human cheek epithelial cell.]
50 µm
(b) Brightfield (stained specimen). Staining
with various dyes enhances contrast, but
most staining procedures require that cells
be fixed (preserved).
(c) Phase-contrast. Enhances contrast
in unstained cells by amplifying
variations in density within specimen;
especially useful for examining living,
unpigmented cells.
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Figure 6.1 A cell and its skeleton viewed by
fluorescence microscopy
10 µm
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Figure 6.2 The size range of cells
10 m
Human height
Length of some
nerve and
muscle cells
Unaided eye
1m
0.1 m
Chicken egg
1 cm
Frog egg
Most plant and
animal cells
10 µm
1 µm
100 nm
nucleus
Nucleus
Most bacteria
Most bacteria
Mitochondrion
Smallest bacteria
Viruses
Ribosomes
10 nm
Electron microscope
100 µm
Light microscope
1 mm
Proteins
Lipids
1 nm
0.1 nm
Small molecules
Atoms
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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
Figure 6.6 A prokaryotic cell
Pili: attachment structures on
the surface of some prokaryotes
Nucleoid: region where
the cell’s DNA is located (not
enclosed by a membrane)
Ribosomes: organelles that
synthesize proteins
Plasma membrane: membrane
enclosing the cytoplasm
Cell wall: rigid structure outside
the plasma membrane
Capsule: jelly-like outer coating
of many prokaryotes
0.5 µm
(a) A typical
rod-shaped bacterium
Flagella: locomotion
organelles of
some bacteria
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(b) A thin section through the
bacterium Bacillus coagulans
(TEM)
Figure 6.7 Geometric relationships between
surface area and volume
Surface area increases while
total volume remains constant
5
1
1
Total surface area
(height  width 
number of sides 
number of boxes)
6
150
750
Total volume
(height  width  length
 number of boxes)
1
125
125
Surface-to-volume
ratio
(surface area  volume)
6
12
6
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Figure 6.8 The plasma membrane
Outside of cell
Carbohydrate side chain
Hydrophilic
region
Inside of cell
0.1 µm
Hydrophobic
region
(a) TEM of a plasma
membrane. The
plasma membrane,
here in a red blood
cell, appears as a
pair of dark bands
separated by a
light band.
Hydrophilic
region
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Phospholipid
Proteins
(b) Structure of the plasma membrane
Figure 6.9 Exploring Animal and Plant Cells Animal Cell
ENDOPLASMIC RETICULUM (ER)
Rough ER
Smooth ER
Nuclear envelope
Nucleolus
NUCLEUS
Chromatin
Flagelium
Plasma membrane
Centrosome
CYTOSKELETON
Microfilaments
Intermediate filaments
Ribosomes
Microtubules
Microvilli
Golgi apparatus
Peroxisome
Mitochondrion
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Lysosome
In animal cells but not plant cells:
Lysosomes
Centrioles
Flagella (in some plant sperm)
Animal and Plant Cells: Plant Cell
Nuclear envelope
Nucleolus
Chromatin
NUCLEUS
Centrosome
Rough
endoplasmic
reticulum Smooth
endoplasmic
reticulum
Ribosomes ( small brown dots )
Central vacuole
Tonoplast
Golgi apparatus
Microfilaments
Intermediate
filaments
CYTOSKELETON
Microtubules
Mitochondrion
Peroxisome
Plasma membrane
Chloroplast
Cell wall
Plasmodesmata
Wall of adjacent cell
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In plant cells but not animal cells:
Chloroplasts
Central vacuole and tonoplast
Cell wall
Plasmodesmata
Figure 6.10 The nucleus and its envelope
Nucleus
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Rough ER
Surface of nuclear envelope.
TEM of a specimen prepared by
a special technique known as
freeze-fracture.
0.25 µm
Ribosome
1 µm
Close-up of nuclear
envelope
Pore complexes (TEM). Each pore is ringed
by protein particles.
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Nuclear lamina (TEM). The netlike lamina
lines the inner surface of the nuclear envelope.
Figure 6.11 Ribosomes
Ribosomes
ER
Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Large
subunit
0.5 µm
TEM showing ER and ribosomes
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Small
subunit
Diagram of a ribosome
Figure 6.12 Endoplasmic reticulum (ER)
Smooth ER
Rough ER
Nuclear
envelope
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
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Transitional ER
Rough ER
200 µm
Figure 6.13 The Golgi apparatus
Golgi
apparatus
cis face
(“receiving” side of
Golgi apparatus)
1 Vesicles move 2 Vesicles coalesce to
6 Vesicles also
from ER to Golgi form new cis Golgi cisternae
transport certain
Cisternae
proteins back to ER
3 Cisternal
maturation:
Golgi cisternae
move in a cisto-trans
direction
5 Vesicles transport specific
proteins backward to newer
Golgi cisternae
0.1 0 µm
4 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)
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TEM of Golgi apparatus
Figure 6.14 Lysosomes
Nucleus
1 µm
Lysosome containing
two damaged organelles
1µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Lysosome contains Food vacuole fuses Hydrolytic
active hydrolytic
enzymes digest
with lysosome
enzymes
food particles
Digestive
enzymes
Lysosome fuses with
vesicle containing
damaged organelle
Lysosome
Plasma membrane
Lysosome
Lysosome
Hydrolytic enzymes
digest organelle
components
Digestion
Food vacuole
(a) Phagocytosis: lysosome digesting food
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Digestion
Vesicle containing
damaged mitochondrion
(b) Autophagy: lysosome breaking down damaged organelle
Figure 6.15 The plant cell vacuole
Central vacuole
Cytosol
Tonoplast
Nucleus
Central
vacuole
Cell wall
Chloroplast
5 µm
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Figure 6.16 Review: relationships among organelles of
the endomembrane system
1 Nuclear envelope is
connected to rough ER,
which is also continuous
with smooth ER
Nucleus
Rough ER
Smooth ER
Nuclear envelope
3
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Figure 6.16 Review: relationships among organelles of
the endomembrane system
1 Nuclear envelope is
connected to rough ER,
which is also continuous
with smooth ER
Nucleus
Rough ER
2 Membranes and proteins
produced by the ER flow in
the form of transport vesicles
to the Golgi
Smooth ER
cis Golgi
Nuclear envelope
Transport
vesicle
3 Golgi pinches off transport
vesicles and other vesicles that
give rise to lysosomes and
vacuoles
trans Golgi
4 Lysosome available 5 Transport vesicle carries
for fusion with another proteins to plasma
vesicle for digestion
membrane for secretion
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 6.16 Review: relationships among organelles of
the endomembrane system
1 Nuclear envelope is
connected to rough ER,
which is also continuous
with smooth ER
Nucleus
Rough ER
2 Membranes and proteins
produced by the ER flow in
the form of transport vesicles
to the Golgi
Smooth ER
cis Golgi
Nuclear envelope
Transport
vesicle
3 Golgi pinches off transport
vesicles and other vesicles that
give rise to lysosomes and
vacuoles
trans Golgi
Plasma
membrane
4 Lysosome available 5 Transport vesicle carries 6 Plasma membrane expands
for fusion with another proteins to plasma
by fusion of vesicles; proteins
vesicle for digestion
membrane for secretion
are secreted from cell
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Figure 6.17 The mitochondrion, site of cellular respiration
Mitochondrion
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
Inner
membrane
Cristae
Matrix
Mitochondrial
DNA
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100 µm
Figure 6.18 The chloroplast, site of photosynthesis
Chloroplast
Ribosomes
Stroma
Chloroplast
DNA
Inner and outer
membranes
Granum
1 µm
Thylakoid
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Figure 6.19 Peroxisomes
Chloroplast
Peroxisome
Mitochondrion
1 µm
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Figure 6.20 The cytoskeleton
Microtubule
0.25 µm
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Microfilaments
Figure 6.21 Motor proteins and the cytoskeleton
ATP
Vesicle
Receptor for
motor protein
Motor protein
(ATP powered)
Microtubule
of cytoskeleton
(a) Motor proteins that attach to receptors on organelles can “walk”
the organelles along microtubules or, in some cases, microfilaments.
Vesicles
Microtubule
0.25 µm
(b) Vesicles containing neurotransmitters migrate to the tips of nerve cell
axons via the mechanism in (a). In this SEM of a squid giant axon, two
vesicles can be seen moving along a microtubule. (A separate part of the
experiment provided the evidence that they were in fact moving.)
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Table 6.1 The Structure and Function of the Cytoskeleton
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Figure 6.22 Centrosome containing a pair of centrioles
Centrosome
Microtubule
Centrioles
0.25 µm
Longitudinal section Microtubules Cross section
of one centriole
of the other centriole
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Figure 6.23 A comparison of the beating of flagella and cilia
(a) Motion of flagella. A flagellum
usually undulates, its snakelike
motion driving a cell in the same
direction as the axis of the
flagellum. Propulsion of a human
sperm cell is an example of
flagellate locomotion (LM).
Direction of swimming
1 µm
(b) Motion of cilia. Cilia have a backand-forth motion that moves the
cell in a direction perpendicular
to the axis of the cilium. A dense
nap of cilia, beating at a rate of
about 40 to 60 strokes a second,
covers this colpidium, a
freshwater protozoan (SEM).
Direction of organism’s movement
Direction of
active stroke
Direction of
recovery stroke
15 µm
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Figure 6.24 Ultrastructure of a eukaryotic flagellum
or cilium
Outer microtubule
doublet
Dynein arms
0.1 µm
Central
microtubule
Outer doublet
cross-linking
proteins
Microtubules
Plasma
membrane
Basal body
Radial
spoke
(b) A cross section through the cilium shows the ”9 + 2“
arrangement of microtubules (TEM). The outer microtubule doublets and the two central microtubules are
held together by cross-linking proteins (purple in art),
including the radial spokes. The doublets also have
attached motor proteins, the dynein arms (red in art).
0.5 µm
(a) A longitudinal section of a cilium shows microtubules running the length of the structure (TEM).
0.1 µm
Triplet
(c) Basal body: The nine outer doublets of a
cilium or flagellum extend into the basal body,
where each doublet joins another microtubule
to form a ring of nine triplets. Each triplet is
connected to the next by non-tubulin proteins
(blue). The two central microtubules terminate
above the basal body (TEM).
Cross section of basal body
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Plasma
membrane
Figure 6.25 How dynein “walking” moves flagella and cilia
Microtubule
doublets
ATP
Dynein arm
(a) Powered by ATP, the dynein arms of one microtubule doublet
grip the adjacent doublet, push it up, release, and then grip again.
If the two microtubule doublets were not attached, they would slide
relative to each other.
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ATP
Outer doublets
cross-linking
proteins
Anchorage
in cell
(b) In a cilium or flagellum, two adjacent doublets cannot slide far because
they are physically restrained, so they bend. (Only two of the nine outer
doublets in Figure 6.24b are shown here.)
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1
3
2
(c) Localized, synchronized activation of many dynein arms probably
causes a bend to begin at the base of the Cilium or flagellum and
move outward toward the tip. Many successive bends, such as the
ones shown here to the left and right, result in a wavelike motion.
In this diagram, the two central microtubules and the cross-linking
proteins are not shown.
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Figure 6.26 A structural role of microfilaments
Microvillus
Plasma membrane
Microfilaments (actin
filaments)
Intermediate filaments
0.25 µm
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Figure 6.27 Microfilaments and motility
Muscle cell
Actin filament
Myosin filament
Myosin arm
(a) Myosin motors in muscle cell contraction.
Cortex (outer cytoplasm):
gel with actin network
Inner cytoplasm: sol
with actin subunits
Extending
pseudopodium
(b) Amoeboid movement .
Nonmoving
cytoplasm (gel)
Chloroplast
Streaming
cytoplasm
(sol)
Parallel actin
filaments
(b) Cytoplasmic streaming in plant cells.
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Cell wall
Figure 6.28 Plant cell walls
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
Plant cell walls
Plasmodesmata
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Figure 6.29 Extracellular matrix (ECM) of an animal cell
Collagen fibers
are embedded
in a web of
proteoglycan
complexes.
A proteoglycan
complex consists
of hundreds of
proteoglycan
molecules attached
noncovalently to a
single long polysaccharide molecule.
EXTRACELLULAR FLUID
Fibronectin
attaches the
ECM to
integrins
embedded in
the plasma
membrane.
Plasma
membrane
Integrin
Microfilaments
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CYTOPLASM
Integrins are membrane
proteins that are bound
to the ECM on one side
and to associated
proteins attached to
microfilaments on the
other. This linkage can
transmit stimuli
between the cell’s
external environment
and its interior and can
result in changes in cell
behavior.
Polysaccharide
molecule
Carbohydrates
Core
protein
Proteoglycan
molecule
Figure 6.30 Plasmodesmata between plant cells
Cell walls
Interior
of cell
Interior
of cell
0.5 µm
Plasmodesmata
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Plasma membranes
Figure 6.31 Exploring Intercellular Junctions in Animal Tissues
TIGHT JUNCTIONS
At tight junctions, the membranes of
neighboring cells are very tightly pressed
against each other, bound together by
specific proteins (purple). Forming continuous seals around the cells, tight junctions
prevent leakage of extracellular fluid across
a layer of epithelial cells.
Tight junction
Tight junctions prevent
fluid from moving
across a layer of cells
0.5 µm
DESMOSOMES
Desmosomes (also called anchoring
junctions) function like rivets, fastening cells
together into strong sheets. Intermediate
filaments made of sturdy keratin proteins
anchor desmosomes in the cytoplasm.
Tight junctions
Intermediate
filaments
Desmosome
Gap
junctions
Space
between Plasma membranes
cells
of adjacent cells
1 µm
Extracellular
matrix
Gap junction
0.1 µm
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GAP JUNCTIONS
Gap junctions (also called communicating
junctions) provide cytoplasmic channels from
one cell to an adjacent cell. Gap junctions
consist of special membrane proteins that
surround a pore through which ions, sugars,
amino acids, and other small molecules may
pass. Gap junctions are necessary for communication between cells in many types of tissues,
including heart muscle and animal embryos.
5 µm
Figure 6.32 The emergence of cellular functions from
the cooperation of many organelles
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