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Chapter 4
Cell Structure and
Function
Lectures by
Gregory Ahearn
University of North Florida
Copyright © 2009 Pearson Education, Inc..
4.1 What Features Are Shared By All Cells?
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Cells are the smallest unit of life.
Cells are enclosed by a plasma membrane.
Cells use DNA as a hereditary blueprint.
Cells contain cytoplasm, which is all the
material inside the plasma membrane and
outside the DNA-containing region.
 Cells obtain energy and nutrients from their
environment.
Copyright © 2009 Pearson Education Inc.
4.1 What Features Are Shared By All Cells?
Copyright © 2009 Pearson Education Inc.
4.1 What Features Are Shared By All Cells?
tallest trees
10 m
1m
10 cm
1 cm
adult human
visible with unaided
human eye
 Relative sizes
Diameter
100 m
chicken egg
frog embryo
10 mm
1 mm
Units of measurement:
1 meter (m) = 39.37 inches
1 centimeter (cm) = 1/100 m
1 millimeter (mm) = 1/1,000 m
1 micrometer (mm) = 1/1,000,000 m
1 nanometer (nm) = 1/1,000,000,000 m
10 nm
1 nm
0.1 nm
visible with
special electron
microscopes
100 nm
most eukaryotic cells
visible with conventional
electron microscope
100 mm
visible with
light microscope
1 mm
mitochondrion
most bacteria
virus
proteins
diameter of DNA double helix
atoms
Fig. 4-1
Copyright © 2009 Pearson Education Inc.
4.1 What Features Are Shared By All Cells?
 Cell function limits cell size.
• Diffusion of molecules across cell membranes
limits the diameter of cells.
• As cells get bigger, their nutrient and waste
elimination needs grow faster than the
membrane area to accommodate them.
Copyright © 2009 Pearson Education Inc.
4.1 What Features Are Shared By All Cells?
 The volume of cytoplasm grows faster than the
plasma membrane area.
Fig. 4-2
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4.2 How Do Prokaryotic And Eukaryotic
Cells Differ?
 There are two kinds of cells.
• Prokaryotic cells
• Are found only in two groups of singlecelled organisms—the bacteria and
archaea
• Eukaryotic cells
• Are structurally more complex cells
• Possess a membrane-enclosed nucleus
• Probably arose from prokaryotic cells
Copyright © 2009 Pearson Education Inc.
4.2 How Do Prokaryotic And Eukaryotic
Cells Differ?
PLAY
Animation—Cell Structure
Copyright © 2009 Pearson Education Inc.
4.3 What Are The Main Features Of
Eukaryotic Cells?
 Eukaryotic cells differ from prokaryotic cells
because the former possess a number of
membrane-enclosed organelles that perform
specific cell functions.
• Nucleus: contains DNA
• Mitochondria: produce energy
• Endoplasmic reticulum: synthesizes membrane
components and lipids
• Golgi apparatus: molecule sorting center
• Lysosomes: digest cellular membranes or defective
organelles
• Microtubules: make up the cytoskeleton
Copyright © 2009 Pearson Education Inc.
4.3 What Are The Main Features Of
Eukaryotic Cells?
 A generalized animal cell
flagellum
cytoplasm
rough endoplasmic
reticulum
ribosome
lysosome
nuclear pore
chromatin (DNA)
nucleus
nucleolus
nuclear envelope
centriole
intermediate
filaments
plasma
membrane
Golgi
apparatus
vesicle
microtubules
free ribosome
smooth
endoplasmic
reticulum
Copyright © 2009 Pearson Education Inc.
vesicle
mitochondrion
Fig. 4-3
Tour of an Animal Cell
Suggested Media Enhancement:
Tour of an Animal Cell
To access this animation go to folder C_Animations_and_Video_Files
and open the BioFlix folder.
Copyright © 2009 Pearson Education Inc.
4.3 What Are The Main Features Of
Eukaryotic Cells?
 A generalized plant cell
microtubules
(part of cytoskeleton)
mitochondrion
chloroplast
central
vacuole
Golgi
apparatus
plasmodesma
smooth
endoplasmic
reticulum
vesicle
cell wall
rough
endoplasmic
reticulum
plasma
membrane
nucleolus
nuclear pore
chromatin
nuclear
envelope
intermediate
filaments
nucleus
ribosomes
free ribosome
Fig. 4-4
Copyright © 2009 Pearson Education Inc.
Tour of a Plant Cell
Suggested Media Enhancement:
Tour of a Plant Cell
To access this animation go to folder C_Animations_and_Video_Files
and open the BioFlix folder.
Copyright © 2009 Pearson Education Inc.
4.4 What Role Does The Nucleus Play?
 The nucleus is the largest organelle
in the cell.
• It is bounded by a nuclear envelope.
• It contains granular-looking chromatin.
• It contains the nucleolus.
Copyright © 2009 Pearson Education Inc.
4.4 What Role Does The Nucleus Play?
 The nucleus
nuclear
envelope
nucleolus
nuclear
pores
nucleus
nuclear
pores
chromatin
(a) Structure of the nucleus
(b) Yeast cell
Fig. 4-5
Copyright © 2009 Pearson Education Inc.
4.4 What Role Does The Nucleus Play?
 The nuclear envelope is a double
membrane.
• The membrane is perforated with channels
called nuclear pores.
• Some smaller materials can move through the
pores, while others, such as DNA, are
excluded.
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4.4 What Role Does The Nucleus Play?
 The nucleus contains chromosomes.
• DNA and protein are closely associated in the nucleus
in chromatin.
• Chromatin can become condensed into
chromosomes.
chromatin
chromosome
Fig. 4-6
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4.4 What Role Does The Nucleus Play?
 Ribosomes are composed of RNA and
proteins, and serve as a “workbench” for the
manufacture of proteins.
Copyright © 2009 Pearson Education Inc.
4.4 What Role Does The Nucleus Play?
 Ribosome components are made at the
nucleolus.
• A darkly staining region in the nucleus is
called a nucleolus.
• The nucleolus contains DNA, RNA, proteins,
and ribosomes in various stages of
construction.
• This is the site where components of
ribosomes are constructed.
• Ribosome components leave the nucleus and
are assembled in the cytoplasm.
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 The plasma membrane isolates the cell, and
alternately, helps it interact with its
environment.
• The phospholipid bilayer contains globular
proteins that regulate the transport of
molecules into and out of the cell.
• Plant cells also have a rigid structure outside
the plasma membrane, called a cell wall,
which forms a protective coating.
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 The endoplasmic reticulum (ER) forms
channels within the cytoplasm.
• There are two kinds of ER membranes:
• Rough endoplasmic reticulum: is studded
with ribosomes
• Smooth endoplasmic reticulum: has no
ribosomes
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 The endoplasmic reticulum
ribosomes
smooth ER
rough ER
smooth ER
rough ER
vesicles
(a) Endoplasmic reticulum may be rough or smooth
(b) Smooth and rough ER
Fig. 4-7
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 The rough ER is the site where proteins are
made.
 The smooth ER makes phospholipids and
cholesterol.
 Together, the rough and smooth ER are the
sites of new membrane synthesis for the
cell.
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 The Golgi apparatus sorts, chemically
alters, and packages important molecules.
• This organelle looks like a stack of flattened
sacs.
• Its membranes are derived from the ER.
• Vesicles containing preformed molecules from
the ER are transferred to the Golgi for further
processing.
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 The Golgi apparatus
Protein-carrying
vesicles from the
ER merge with the
Golgi apparatus
Golgi
apparatus
Vesicles carrying
modified proteins
leave the Golgi
apparatus
Fig. 4-8
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 Once the molecular work of the Golgi has
been done, new vesicles bud off and travel
elsewhere in the cytoplasm, where they fuse
with membranes of other organelles, such
as the plasma membrane.
 A major role of the Golgi is to add sugar
molecules to proteins formed in the ER and
to pass them on to other places in the cell.
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 We can follow the travels of a secreted
protein.
• An antibody protein is synthesized on
ribosomes of the rough ER.
• Formed antibody is packaged into vesicles
that travel to the Golgi, where carbohydrates
are attached to protein to make an antibody.
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 We can follow the travels of a secreted
protein (continued).
• The vesicle containing antibody leaves the
Golgi and goes to the plasma membrane,
where it fuses with it.
• The antibody inside the vesicle is released to
the outside of the cell (to the blood), where it
helps defend the body against infection.
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
PLAY
Animation—Membrane Traffic
Copyright © 2009 Pearson Education Inc.
4.5 What Roles Do Membranes Play In
Eukaryotic Cells?
 Lysosomes are vesicles that serve as the
cell’s digestive system.
• They are formed as buds from the Golgi.
• Lysosomes contain digestive enzymes that
they receive from Golgi during their
production.
• In the cytoplasm, they digest defective
organelles or pieces of membrane into
component parts that can be recycled.
Copyright © 2009 Pearson Education Inc.
4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Vacuoles regulate water and store
substances.
• They are fluid-filled sacs surrounded by a
single membrane.
• Many plant cells have a large central vacuole.
• Vacuoles hold water and help maintain the
proper water balance of the cell.
• Vacuoles can also serve as dump sites for
hazardous waste that can’t be excreted.
• They can also store sugars and amino acids,
which can be used for energy.
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4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Mitochondria extract energy from food
molecules.
• Mitochondria provide the energy needed for all
cellular processes.
• Energy is obtained from sugar molecules in
mitochondria and is stored in ATP molecules.
• Once formed, ATP can be used anywhere in
the cell where energy is needed.
• Mitochondria have a complex set of outer and
inner membranes, and both sets are used in
the process of energy production.
Copyright © 2009 Pearson Education Inc.
4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Chloroplasts capture solar energy.
• Only plant cells contain chloroplasts.
• Chloroplasts capture energy from sunlight and
store it in sugar molecules.
• They are the site of photosynthesis, the
process upon which all life depends.
• Like mitochondria, chloroplasts contain both
outer and inner membranes.
Copyright © 2009 Pearson Education Inc.
4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 The cytoskeleton provides shape, support,
and movement.
• All organelles in the cell do not float about the
cytoplasm, but instead, are attached to a
network of protein fibers called the
cytoskeleton.
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4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Several type of protein fibers make up the
cytoskeleton.
• Microfilaments: thin fibers
• Intermediate filaments: medium-sized fibers
• Microtubules: thick fibers
Copyright © 2009 Pearson Education Inc.
4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 The cytoskeleton
plasma
membrane
microfilaments
mitochondrion
microtubules (red)
intermediate
filaments
ribosomes
endoplasmic
reticulum
microtubule
nucleus
vesicle
microfilaments (blue)
(a) Components of the cytoskeleton
(b) Cell with stained cytoskeleton
Fig. 4-9
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4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Cilia and flagella move the cell or move fluid
past the cell.
• Cilia and flagella are slender, movable
extensions of the plasma membrane.
• They contain microtubules that extend along
their length.
• They may be used to move small animals or
particle-containing fluids past a surface.
Copyright © 2009 Pearson Education Inc.
4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Cilia and flagella move the cell or move fluid
past the cell (continued).
• Differences between cilia and flagella lie in
their length, number, and the direction of force
generated.
• Cilia are shorter and more numerous than
flagella.
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4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Cilia provide force parallel to the plasma
membrane, which can be described as a
“rowing” motion.
propulsion of fluid
power stroke
plasma membrane
return stroke
cilia lining
the trachea
(a) Cilium
Fig. 4-10a
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4.6 What Other Structures Play Key Roles
In Eurkaryotic Cells?
 Flagella provide a force perpendicular to plasma
membrane, like the engine on a motorboat.
direction of locomotion
propulsion of fluid
continuous propulsion
flagellum
of human
sperm
(b) Flagellum
Fig. 4-10b
Copyright © 2009 Pearson Education Inc.
4.7 What Are The Features Of Prokaryotic
Cells?
 Prokaryotic cells are much smaller than
eukaryotic cells, are more abundant, and
are very reproductively successful.
 The are very small and have a simple
internal structure.
 They are surrounded by a stiff cell wall,
which provides shape and protection.
 Some move with a whiplike flagellum.
Copyright © 2009 Pearson Education Inc.
4.7 What Are The Features Of Prokaryotic
Cells?
 A single, circular strand of DNA is attached
to the plasma membrane and is
concentrated in an area called the nucleoid,
which lacks a membrane.
 There are no membrane-enclosed
organelles.
 The cytoplasm contains ribosomes used for
protein synthesis.
Copyright © 2009 Pearson Education Inc.
4.7 What Are The Features Of Prokaryotic
Cells?
 A generalized prokaryotic cell
chromosome
(nucleoid region)
ribosomes
food granule
prokaryotic
flagellum
cell wall
cytoplasm
plasma membrane
Fig. 4-11
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