Chapter 4 · 2015. 11. 12. · Introduction •In 1665, Hooke examined a piece of cork under a...
Transcript of Chapter 4 · 2015. 11. 12. · Introduction •In 1665, Hooke examined a piece of cork under a...
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Campbell Biology: Concepts & Connections, Eighth Edition REECE • TAYLOR • SIMON • DICKEY • HOGAN
Chapter 4
Lecture by Edward J. Zalisko
A Tour of the Cell
© 2015 Pearson Education, Inc.
Introduction
• Cells have a cytoskeleton that
• provides support and
• allows some cells to crawl and others to swim.
• Our understanding of nature often goes hand in
hand with the invention and refinement of
instruments that extend our senses.
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Introduction
• In 1665, Hooke examined a piece of cork under a
crude microscope and identified “little rooms” as
cells.
• Leeuwenhoek, working at about the same time,
used more refined lenses to describe living cells
from blood, sperm, and pond water.
• Since the days of Hooke and Leeuwenhoek,
improved microscopes have vastly expanded our
view of the cell.
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© 2015 Pearson Education, Inc.
Figure 4.0-1
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Figure 4.0-2
Introduction to the Cell
Chapter 4: Big Ideas
The Nucleus and
Ribosomes
The Endomembrane
System
Energy-Converting
Organelles
The Cytoskeleton and
Cell Surfaces
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INTRODUCTION TO THE CELL
4.1 Microscopes reveal the world of the cell
• A variety of microscopes have been developed for
a clearer view of cells and cellular structure.
• The first microscopes were light microscopes. In a
light microscope (LM), visible light passes
through a specimen, then through glass lenses,
and finally is projected into the viewer’s eye.
• Specimens can be magnified by up to 1,000 times.
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4.1 Microscopes reveal the world of the cell
• Magnification is the increase in an object’s image
size compared with its actual size.
• Resolution is a measure of the clarity of an image.
In other words, it is the ability of an instrument to
show two nearby objects as separate.
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4.1 Microscopes reveal the world of the cell
• Microscopes have limitations.
• The human eye and the microscope have limits of
resolution—the ability to distinguish between small
structures.
• Therefore, the light microscope cannot provide the
details of a small cell’s structure.
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4.1 Microscopes reveal the world of the cell
• Using light microscopes, scientists studied
• microorganisms,
• animal and plant cells, and
• some structures within cells.
• In the 1800s, these studies led to cell theory,
which states that
• all living things are composed of cells and
• all cells come from other cells.
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Figure 4.1a
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Figure 4.1b
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Figure 4.1c
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Figure 4.1d
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Figure 4.1e-0
Human height
Length of some
nerve and
muscle cells
Chicken egg
Frog egg
Paramecium
Human egg
Most plant and
animal cells
Nucleus
Most bacteria
Mitochondrion
Smallest bacteria
Viruses
Ribosome
Proteins
Lipids
Small
molecules
Atoms
Un
aid
ed
eye
Lig
ht
mic
ros
co
pe
Ele
ctr
on
mic
ros
co
pe
10 m
1 m
100 mm
(10 cm)
10 mm
(1 cm)
1 mm
100 nm
10 nm
1 nm
0.1 nm
100 μm
10 μm
1 μm
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Figure 4.1e-1
Human height
Length of some
nerve and
muscle cells
Chicken egg
Frog egg
Paramecium
Human egg U
na
ide
d e
ye
10 m
1 m
100 mm
(10 cm)
10 mm
(1 cm)
1 mm
100 μm
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Figure 4.1e-2
Frog egg
Paramecium
Human egg
Most plant and
animal cells
Nucleus
Most bacteria
Mitochondrion
Smallest bacteria
Viruses
Ribosome
Proteins
Lipids
Small
molecules
Atoms
Lig
ht
mic
ros
co
pe
Ele
ctr
on
mic
ros
co
pe
1 mm
100 nm
10 nm
1 nm
0.1 nm
100 μm
10 μm
1 μm
4.1 Microscopes reveal the world of the cell
• Beginning in the 1950s, scientists started using a
very powerful microscope called the electron
microscope (EM) to view the ultrastructure of
cells.
• Instead of light, EM uses a beam of electrons.
• Electron microscopes can
• resolve biological structures as small as 2
nanometers and
• magnify up to 100,000 times.
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4.1 Microscopes reveal the world of the cell
• Scanning electron microscopes (SEMs) study
the detailed architecture of cell surfaces.
• Transmission electron microscopes (TEMs)
study the details of internal cell structure.
• Differential interference light microscopes amplify
differences in density so that structures in living
cells appear almost three-dimensional.
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4.2 The small size of cells relates to the need to exchange materials across the plasma membrane
• Cell size must
• be large enough to house DNA, proteins, and
structures needed to survive and reproduce, but
• remain small enough to allow for a surface-to-
volume ratio that will allow adequate exchange with
the environment.
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© 2015 Pearson Education, Inc.
Figure 4.2a
Total volume
3
3
1
1
2 6
Total surface
area
Surface-to-
volume ratio
27 units3 27 units3
54 units2 162 units2
4.2 The small size of cells relates to the need to exchange materials across the plasma membrane
• The plasma membrane forms a flexible boundary
between the living cell and its surroundings.
• Phospholipids form a two-layer sheet called a
phospholipid bilayer in which
• hydrophilic heads face outward, exposed to water,
and
• hydrophobic tails point inward, shielded from water.
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4.2 The small size of cells relates to the need to exchange materials across the plasma membrane
• Membrane proteins are embedded in the lipid
bilayer.
• Some proteins form channels (tunnels) that shield
ions and other hydrophilic molecules as they pass
through the hydrophobic center of the membrane.
• Other proteins serve as pumps, using energy to
actively transport molecules into or out of the cell.
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Figure 4.2b
Outside cell
Inside cell
Hydrophilic
heads
Hydrophobic
tails
Phospholipid
Channel
protein
Hydrophilic
regions of
a protein
Hydrophobic
regions of
a protein
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Figure 4.UN01
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
Capsule Bacterial
chromosome
A typical rod-shaped
bacterium
A colorized TEM of the
bacterium Escherichia coli
Flagella
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Figure 4.3-1 Fimbriae
Ribosomes
Nucleoid
Plasma
membrane
Cell wall
Capsule Bacterial
chromosome
A typical rod-shaped
bacterium Flagella
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Figure 4.3-2
A colorized TEM of the
bacterium Escherichia coli
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
Smooth
endoplasmic
reticulum
Golgi apparatus
Lysosome
Mitochondrion
Centrosome
with pair of
centrioles
Plasma
membrane
Peroxisome
Intermediate
filament
Microfilament
Microtubule
CYTOSKELETON
NUCLEUS Nuclear envelope
Nucleolus Chromatin
Ribosomes
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Figure 4.4b
Rough
endoplasmic
reticulum
Smooth
endoplasmic
reticulum
NUCLEUS Nuclear envelope Nucleolus Chromatin
Ribosomes
Plasma
membrane
Peroxisome
Mitochondrion
Microfilament Microtubule
CYTOSKELETON
Cell wall of
adjacent cell Golgi
apparatus
Plasmodesma
Cell wall
Chloroplast
Central
vacuole
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THE NUCLEUS AND RIBOSOMES
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 nuclear envelope 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
Nucleolus Nuclear
envelope
Endoplasmic
reticulum
Ribosome
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
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. Smooth ER lacks attached ribosomes.
2. Rough ER has 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
mRNA
1
2
3
4
Bound ribosome
Transport vesicle
buds off
Secretory
protein
inside trans-
port vesicle
Sugar
chain
Rough ER
Glycoprotein
Growing
polypeptide
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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Figure 4.9
Golgi apparatus
1
2
3
4
“Receiving” side of Golgi apparatus
Transport vesicle
from the ER
Transport
vesicle from
the Golgi
“Shipping” side of
Golgi apparatus
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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Animation: Lysosome Formation
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© 2015 Pearson Education, Inc.
Figure 4.10a-1
Digestive
enzymes
Lysosome
Plasma membrane
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Figure 4.10a-2
Digestive
enzymes
Lysosome
Food vacuole
Plasma membrane
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Figure 4.10a-3
Digestive
enzymes
Lysosome
Food vacuole
Plasma membrane
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Figure 4.10a-4
Digestive
enzymes
Lysosome
Food vacuole
Plasma membrane
Digestion
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Figure 4.10b-1
Lysosome
Vesicle containing
damaged mitochondrion
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Figure 4.10b-2
Lysosome
Vesicle containing
damaged mitochondrion
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Figure 4.10b-3
Lysosome
Digestion Vesicle containing
damaged mitochondrion
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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Video: Paramecium Vacuole
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© 2015 Pearson Education, Inc.
Figure 4.11a
Contractile
vacuoles
Nucleus
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Figure 4.11b
Central vacuole
Chloroplast
Nucleus
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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© 2015 Pearson Education, Inc.
Figure 4.12
Nucleus
Smooth ER
Rough ER
Transport vesicle
Lysosome
Nuclear envelope
Golgi apparatus
Plasma
membrane
Transport
vesicle
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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© 2015 Pearson Education, Inc.
ENERGY-CONVERTING
ORGANELLES
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 mitochondrial matrix 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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© 2015 Pearson Education, Inc.
Figure 4.13
Mitochondrion
Intermembrane
space
Outer
membrane
Inner
membrane
Crista
Matrix
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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© 2015 Pearson Education, Inc.
Figure 4.14
Chloroplast
Granum
Stroma
Inner and
outer membranes
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 endosymbiont theory states that
• mitochondria and chloroplasts were formerly small
prokaryotes and
• they began living within larger cells.
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© 2015 Pearson Education, Inc.
Figure 4.15 Endoplasmic
reticulum Nucleus
Ancestor of
eukaryotic cells (host cell)
Mitochondrion
Engulfing of
photosynthetic
prokaryote
Mitochondrion
Photosynthetic eukaryote
Chloroplast
Nonphotosynthetic
eukaryote
At least
one cell
Engulfing of oxygen-
using prokaryote
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Figure 4.15-1 Endoplasmic
reticulum Nucleus
Ancestor of
eukaryotic cells (host cell)
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Figure 4.15-2 Endoplasmic
reticulum Nucleus
Ancestor of
eukaryotic cells (host cell)
Mitochondrion
Nonphotosynthetic
eukaryote
Engulfing of oxygen-
using prokaryote
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Figure 4.15-3 Endoplasmic
reticulum Nucleus
Ancestor of
eukaryotic cells (host cell)
Mitochondrion
Engulfing of
photosynthetic
prokaryote
Mitochondrion
Photosynthetic eukaryote
Chloroplast
Nonphotosynthetic
eukaryote
At least
one cell
Engulfing of oxygen-
using prokaryote
© 2015 Pearson Education, Inc.
THE CYTOSKELETON AND
CELL SURFACES
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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Video: Cytoplasmic Streaming
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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
• Intermediate filaments
• 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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© 2015 Pearson Education, Inc.
Figure 4.16-0
Nucleus
Nucleus
Microtubule
25 nm Intermediate filament
10 nm
Microfilament
7 nm
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Figure 4.16-1
Nucleus
Microtubule
25 nm
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Figure 4.16-2
Nucleus
Intermediate filament
10 nm
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Figure 4.16-3
Microfilament
7 nm
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Figure 4.16-4
Nucleus
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Figure 4.16-5
Nucleus
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Figure 4.16-6
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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© 2015 Pearson Education, Inc.
Figure 4.17
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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Video: Paramecium Cilia
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Video: Chlamydomonas
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© 2015 Pearson Education, Inc.
Figure 4.18a
Cilia
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Figure 4.18b
Flagellum
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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Animation: Cilia and Flagella
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© 2015 Pearson Education, Inc.
Figure 4.18c-0
Outer
microtubule
doublet
Central
microtubules
Cross-linking
proteins
Motor proteins
(dyneins)
Plasma membrane
© 2015 Pearson Education, Inc.
Figure 4.18c-1
Outer
microtubule
doublet
Central
microtubules
Cross-linking
proteins
Motor proteins
(dyneins)
© 2015 Pearson Education, Inc.
Figure 4.18c-2
Outer
microtubule
doublet
Central
microtubules
Cross-linking
proteins
Motor proteins
(dyneins)
Plasma
membrane
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
extracellular matrix (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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© 2015 Pearson Education, Inc.
Figure 4.19
Collagen fiber
EXTRACELLULAR FLUID
CYTOPLASM
Glycoprotein
complex with long
polysaccharide
Connecting
glycoprotein
Integrin
Plasma
membrane
Microfilaments
of cytoskeleton
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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Animation: Desmosomes
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Animation: Gap Junctions
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Animation: Tight Junctions
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© 2015 Pearson Education, Inc.
Figure 4.20
Tight junction
Anchoring
junction
Gap junction
Plasma membranes
of adjacent cells
Ions or small molecules Extracellular matrix
Tight junctions
prevent fluid from
moving across a
layer of cells
4.21 Cell walls enclose and support plant cells
• A plant cell, but not an animal cell, has a rigid cell
wall 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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© 2015 Pearson Education, Inc.
Figure 4.21
Vacuole
Plant cell
walls
Plasmodesmata
Primary cell wall
Secondary cell wall
Plasma membrane
Cytosol
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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© 2015 Pearson Education, Inc.
Table 4-22-0
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Table 4-22-1
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Table 4-22-2
You should now be able to
1. Describe the importance of microscopes in
understanding cell structure and function.
2. Describe the two parts of cell theory.
3. Distinguish between the structures of prokaryotic
and eukaryotic cells.
4. Explain how cell size is limited.
5. Describe the structure and functions of cell
membranes.
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You should now be able to
6. Explain why compartmentalization is important in
eukaryotic cells.
7. Compare the structures of plant and animal cells.
Note the function of each cell part.
8. Compare the structures and functions of
chloroplasts and mitochondria.
9. Describe the evidence that suggests that
mitochondria and chloroplasts evolved by
endosymbiosis.
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You should now be able to
10. Compare the structures and functions of
microfilaments, intermediate filaments, and
microtubules.
11. Relate the structure of cilia and flagella to their
functions.
12. Relate the structure of the extracellular matrix to
its functions.
13. Compare the structures and functions of tight
junctions, anchoring junctions, and gap
junctions.
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You should now be able to
14. Relate the structures of plant cell walls and
plasmodesmata to their functions.
15. Describe the four functional categories of
organelles in eukaryotic cells.
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© 2015 Pearson Education, Inc.
Table 4-1
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Figure 4.UN02
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Figure 4.UN03
a. b. c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
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Figure 4.UN04-0
Poles of dividing cell
Mark
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Figure 4.UN04-1
Poles of dividing cell
Mark
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Figure 4.UN04-2