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Chapter 6
A Tour of the Cell
PowerPoint® Lecture Presentations for
Biology
Eighth Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero, updated by Erin Barley with contributions from Joan Sharp
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Overview: The Fundamental Units of Life
• All organisms are made of cells (Cell Theory).
• The cell is the simplest collection of matter
that can live.
• Cell structure is correlated to cellular function.
• All cells are related by their descent from
earlier cells (heredity / reproduction).
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To study cells, biologists use microscopes and the
tools of biochemistry
• Microscopy: Scientists use microscopes to
visualize cells too small to see with the naked
eye.
• In a light microscope (LM), visible light
passes through a specimen and then through
glass lenses, which magnify the image.
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• The quality of an image depends on
– Magnification, the ratio of an object’s image
size to its real size.
– Resolution, the measure of the clarity of the
image, or the minimum distance of two
distinguishable points.
– Contrast, visible differences in parts of the
sample.
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10 m
1m
Human height
Length of some
nerve and
muscle cells
0.1 m
Chicken egg
1 cm
Unaided eye
Frog egg
100 µm
Most plant and
animal cells
10 µm
Nucleus
Most bacteria
1 µm
100 nm
10 nm
Mitochondrion
Smallest bacteria
Viruses
Ribosomes
Proteins
Lipids
1 nm
Small molecules
0.1 nm
Atoms
Electron microscope
1 mm
Light microscope
The size range
of cells
• LMs (light microscopes) can magnify effectively
to about 1,000 times the size of the actual
specimen.
• Various techniques enhance contrast and
enable cell components to be stained or
labeled.
• Most subcellular structures, including
organelles (membrane-enclosed
compartments), are too small to be resolved by
an LM.
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Light
Microscopy
TECHNIQUE
RESULTS
Brightfield
unstained
specimen
(a)
50 µm
(b)
Brightfield
stained
specimen
(c)
Phase-contrast
(d) Differential-
interferencecontrast (Nomarski)
(e )Fluorescence
50 µm
(f) Confocal
50 µm
• Two basic types of electron microscopes
(EMs) are used to study subcellular structures.
• Scanning electron microscopes (SEMs)
focus a beam of electrons onto the surface of
a specimen, providing images that look 3-D.
• Transmission electron microscopes (TEMs)
focus a beam of electrons through a specimen.
• TEMs are used mainly to study the internal
structure of cells.
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Electron
microscopy
TECHNIQUE
RESULTS
Cilia
1 µm
(a) Scanning electron
microscopy (SEM)
Surface
Longitudinal Cross section
section of
of cilium
1 µm
cilium
(b) Transmission electron
microscopy (TEM)
Internal structures
Cell Fractionation
• Cell fractionation takes cells apart and
separates the major organelles from one
another.
• Ultracentrifuges fractionate cells and separate
their component parts by density.
• Cell fractionation enables scientists to
determine the functions of organelles.
• Biochemistry and cytology help correlate cell
function with structure.
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Cell
fractionation
TECHNIQUE
Homogenization
Tissue
cells
1,000 g
(1,000 times the
force of gravity)
10 min
Homogenate
Differential centrifugation : density
Supernatant poured
into next tube
20,000 g
20 min
Pellet rich in
80,000 g
60 min
nuclei and
cellular debris
150,000 g
3 hr
Pellet rich in
mitochondria
(and chloroplasts if cells
are from a plant)
Pellet rich in
“microsomes”
(pieces of plasma
membranes and
cells’ internal
membranes)
Pellet rich in
ribosomes
Cell Fractionation: Part 1
TECHNIQUE
Homogenization
Tissue
cells
Differential centrifugation
Homogenate
Cell Fractionation:
Part 2
TECHNIQUE (cont.)
1,000 g
(1,000 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)
Pellet rich in
“microsomes”
(pieces of plasma
membranes and
cells’ internal
membranes)
Pellet rich in
ribosomes
Eukaryotic cells have internal membranes that
compartmentalize their functions
• Cell = the basic structural and functional unit of
all life. (Cell Theory).
• The basic structural and functional unit of every
organism is one of two types of cells:
prokaryotic or eukaryotic.
• Only organisms of the domains Bacteria and
Archaea consist of prokaryotic cells.
• Protists, fungi, animals, and plants all consist of
eukaryotic cells.
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Comparing Prokaryotic vs. Eukaryotic Cells
• Basic features of all cells:
– Plasma membrane
– Semifluid substance called cytosol (cytoplasm)
– Chromosomes (carry genes) DNA
– Ribosomes (make proteins)
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• Prokaryotic cells are characterized by having
– No nucleus
– DNA in an unbound region called the nucleoid.
– No membrane-bound organelles.
– Cytoplasm bound by the plasma membrane.
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Prokaryotic Cell
Fimbriae
Nucleoid
Ribosomes
Plasma membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 µm
(a) A typical
rod-shaped
bacterium
Flagella
(b) A thin section
through the
bacterium
Bacillus
coagulans (TEM)
• Eukaryotic cells are characterized by having
– DNA in a nucleus that is bounded by a
membranous nuclear envelope.
– Membrane-bound organelles
– Cytoplasm in the region between the plasma
membrane and nucleus.
• Eukaryotic cells are generally much larger than
prokaryotic cells.
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• The plasma membrane is a selective barrier
(semi-permeable) that allows sufficient
passage of oxygen, nutrients, and waste to
service the volume of every cell.
• The general structure of a biological membrane
is a double layer of phospholipids.
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Plasma Membrane
Outside of cell
Inside of
cell
0.1 µm
(a) TEM of a plasma membrane
Carbohydrate side chain
Hydrophilic
region
Hydrophobic
region
Hydrophilic
region
Phospholipid
Proteins
(b) Structure of the plasma membrane
• The logistics of carrying out cellular metabolism
sets limits on the size of cells.
• The surface area to volume ratio of a cell is
critical.
• As the surface area increases by a factor of n2,
the volume increases by a factor of n3
• Small cells have a greater surface area relative
to volume.
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Geometric relationships
between surface area and
volume
Surface area increases while
total volume remains constant
5
1
1
Total surface area
[Sum of the surface areas
(height  width) of all boxes
sides  number of boxes]
Total volume
[height  width  length 
number of boxes]
Surface-to-volume
(S-to-V) ratio
[surface area ÷ volume]
6
150
750
1
125
125
6
1.2
6
Eukaryotic cell: animal cell
Nuclear
envelope
ENDOPLASMIC RETICULUM (ER)
Flagellum
Rough ER
NUCLEUS
Nucleolus
Smooth ER
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
Eukaryotic Cell: Plant Cell
NUCLEUS: Nuclear
Envelope
Nucleolus
Rough endoplasmic reticulum
( Rough ER)
Smooth endoplasmic
reticulum (Smooth ER)
Ribosomes
Chromatin
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Plasmodesmata
Wall of adjacent cell
CYTOSKELETON
:
The Nucleus: Information
Central : DNA
• The nucleus contains most of the cell’s genes
and is usually the most conspicuous organelle.
• The nuclear envelope encloses the nucleus,
separating it from the cytoplasm.
• The nuclear membrane is a double membrane;
each membrane consists of a lipid bilayer.
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The nucleus and its envelope
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Surface of
nuclear envelope
Rough ER
Ribosome
1 µm
0.25 µm
Close-up of nuclear
envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
• Pores regulate the entry and exit of molecules
from the nucleus.
• The shape of the nucleus is maintained by the
nuclear lamina, which is composed of protein.
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• In the nucleus, DNA and proteins form genetic
material called chromatin.
• Chromatin condenses to form discrete
chromosomes.
• The nucleolus is located within the nucleus
and is the site of ribosomal RNA rRNA
synthesis.
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Ribosomes: Protein Factories
• Ribosomes are particles made of ribosomal
RNA and protein.
• Ribosomes carry out protein synthesis in two
locations:
– In the cytosol (free ribosomes)
– On the outside of the endoplasmic reticulum or
the nuclear envelope (bound ribosomes - ER).
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Ribosomes
Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Large
subunit
0.5 µm
TEM showing ER and ribosomes
Small
subunit
Diagram of a ribosome
The endomembrane system regulates protein traffic
and performs metabolic functions in the cell
• Components of the endomembrane system:
– Nuclear envelope
– Endoplasmic reticulum: ER
– Golgi apparatus
– Lysosomes
– Vacuoles
– Plasma membrane
• These components are either continuous or
connected via transfer by vesicles.
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The Endoplasmic Reticulum: Biosynthetic Factory
• The endoplasmic reticulum (ER) accounts for
more than half of the total membrane in many
eukaryotic cells.
• The ER membrane is continuous with the
nuclear envelope.
• There are two distinct regions of ER:
– Smooth ER, which lacks ribosomes.
– Rough ER, with ribosomes studding its
surface.
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Endoplasmic
Smooth ER
Reticulum
ER
Rough ER
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Nuclear
envelope
Transitional ER
Rough ER
200 nm
Functions of Smooth ER
• The smooth ER
– Synthesizes lipids
– Metabolizes carbohydrates
– Detoxifies poison
– Stores calcium Ca+
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Functions of Rough ER
• The rough ER
– Has bound ribosomes, which secrete
glycoproteins (proteins covalently bonded to
carbohydrates).
– Distributes transport vesicles, proteins
surrounded by membranes.
– Is a membrane factory for the cell.
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The Golgi Apparatus: Shipping and Receiving Center
• The Golgi apparatus consists of flattened
membranous sacs called cisternae.
• Functions of the Golgi apparatus:
– Modifies products of the ER
– Manufactures certain macromolecules
– Sorts and packages materials into transport
vesicles.
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Golgi apparatus
cis face
(“receiving” side of
Golgi apparatus)
0.1 µm
Cisternae
trans face
(“shipping” side of
Golgi apparatus)
TEM of Golgi apparatus
Lysosomes: Digestive Compartments
• A lysosome is a membranous sac of hydrolytic
enzymes that can digest macromolecules.
• Lysosomal enzymes can hydrolyze proteins,
fats, polysaccharides, and nucleic acids.
• Helps to breakdown and recycle cell material.
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• Some types of cell can engulf another cell by
phagocytosis; this forms a food vacuole.
• A lysosome fuses with the food vacuole and
digests the molecules.
• Lysosomes also use enzymes to recycle the
cell’s own organelles and macromolecules, a
process called autophagy.
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Lysosomes
Nucleus
1 µm
Vesicle containing
two damaged organelles
1 µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Lysosome
Digestive
enzymes
Plasma
membrane
Lysosome
Peroxisome
Digestion
Food vacuole
Vesicle
(a)
Phagocytosis :engulfs
(b)
Mitochondrion
Autophagy : recycles
Digestion
Vacuoles: Diverse Maintenance Compartments
• Food vacuoles are formed by phagocytosis.
• Contractile vacuoles, found in many
freshwater protists, pump excess water out of
cells: osmoregulation.
• Central vacuoles, found in many mature plant
cells, hold organic compounds and water.
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The plant cell vacuole
Central vacuole
Tonoplast = central vacuole membrane
Cytosol
Nucleus
Central
vacuole
Cell wall
Chloroplast
5 µm
The Endomembrane System
Nucleus
Rough ER
Smooth ER
cis Golgi
trans Golgi
Plasma
membrane
Mitochondria and Chloroplasts change energy
from one form to another
• Mitochondria are the sites of aerobic
cellular respiration, a metabolic process that
generates ATP.
• Chloroplasts, found in plants and algae,
are the sites of photosynthesis.
• Peroxisomes are oxidative organelles.
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• Mitochondria and Chloroplasts:
– Are not part of the endomembrane system
– Have a double membrane
– Have proteins made by free ribosomes
– Contain their own DNA.
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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.
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The mitochondrion = site of cellular respiration
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
Inner
membrane
Cristae
Matrix
0.1 µm
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:
water + carbon dioxide = sugar + oxygen.
• Chloroplasts are found in leaves and other
green organs of plants and in algae.
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• Chloroplast structure includes:
– Thylakoids, membranous sacs, stacked to
form a granum : light dependent reactions.
– Stroma, the internal fluid: Calvin Cycle =
light independent reactions.
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The chloroplast = site of photosynthesis
Chloroplast
Ribosomes
Stroma
Inner and outer
membranes
Granum
Thylakoid
1 µm
Peroxisomes: Oxidation
• Peroxisomes are specialized metabolic
compartments bounded by a single membrane.
• Peroxisomes produce hydrogen peroxide and
convert it to water.
• Oxygen is used to break down different types
of molecules.
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The cytoskeleton is a network of fibers that
organizes structures and activities in the cell
• The cytoskeleton is a network of fibers
extending throughout the cytoplasm.
• It organizes the cell’s structures and activities,
anchoring many organelles.
• It is composed of three types of molecular
structures:
– Microtubules
– Microfilaments
– Intermediate filaments
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The cytoskeleton
Microtubule
0.25 µm
Microfilaments
Roles of the Cytoskeleton: Support, Motility, and
Regulation
• The cytoskeleton helps to support the cell and
maintain its shape.
• It interacts with motor proteins to produce
motility.
• Inside the cell, vesicles can travel along
“monorails” provided by the cytoskeleton.
• Recent evidence suggests that the
cytoskeleton may help regulate biochemical
activities.
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The cytoskeleton
ATP
Vesicle
Receptor for
motor protein
Motor protein Microtubule
(ATP powered) of cytoskeleton
(a)
Microtubule
(b)
Vesicles
0.25 µm
Components of the Cytoskeleton
• Three main types of fibers make up the
cytoskeleton:
– Microtubules are the thickest of the three
components of the cytoskeleton
– Microfilaments, also called actin filaments, are
the thinnest components
– Intermediate filaments are fibers with
diameters in a middle range.
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10 µm
10 µm
10 µm
Column of tubulin dimers
Keratin proteins
Fibrous subunit
(keratins coiled
together)
Actin subunit
25 nm
7 nm


Tubulin dimer
8–12 nm
10 µm
Column of tubulin dimers
25 nm


Tubulin dimer
10 µm
Actin subunit
7 nm
5 µm
Keratin proteins
Fibrous subunit (keratins
coiled together)
8–12 nm
Microtubules
• Microtubules are hollow rods about 25 nm in
diameter and about 200 nm to 25 microns long
• Functions of microtubules:
– Shaping the cell
– Guiding movement of organelles
– Separating chromosomes during cell division
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Centrosomes and Centrioles
• In many cells, microtubules grow out from a
centrosome near the nucleus
• The centrosome = “microtubule-organizing
center” = MTOC
• In animal cells, the centrosome has a pair of
centrioles 9x3 Each centriole has nine
triplets of microtubules arranged in a ring.
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Centrosome
Microtubule
Centrioles
0.25 µm
Longitudinal section Microtubules Cross section
of one centriole
of the other centriole
Cilia and Flagella
• Microtubules control the beating of cilia and
flagella, locomotor appendages of some cells.
• Cilia and flagella differ in their beating patterns.
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Comparison
of the
beating of
Direction of swimming
flagella
and
cilia.
(a) Motion of flagella
5 µm
Direction of organism’s movement
Power stroke Recovery stroke
(b) Motion of cilia
15 µm
• Cilia and flagella share a common
ultrastructure:
– A core of microtubules sheathed by the plasma
membrane.
– A basal body that anchors the cilium or
flagellum.
– A motor protein called dynein, which drives
the bending movements of a cilium or
flagellum.
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Ultrastructure of a eukaryotic
flagellum or motile cilium
Outer microtubule
doublet
0.1 µm
Dynein proteins
Central
microtubule
Radial
spoke
Protein crosslinking outer
doublets
Microtubules
Plasma
membrane
(b) Cross section of
cilium 9x2
Basal body
0.5 µm
(a) Longitudinal
section of cilium
0.1 µm
Triplet
(c) Cross section of basal
body 9x3
Plasma
membrane
• The motor protein, dynein, moves flagella and
cilia by “walking” :
− Dynein arms alternately grab, move, and
release the outer microtubules.
– Protein cross-links limit sliding.
– Forces exerted by dynein arms cause doublets
to curve, bending the cilium or flagellum.
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How dynein “walking”
moves
Microtubule
doublets
ATP
flagella and cilia
Dynein
protein
(a) Effect of unrestrained dynein movement
ATP
Cross-linking proteins
inside outer doublets
Anchorage
in cell
(b) Effect of cross-linking proteins
1
3
2
(c) Wavelike motion
Microfilaments (Actin Filaments)
• Microfilaments are solid rods about 7 nm in
diameter, built as a twisted double chain of
protein actin subunits.
• The structural role of microfilaments is to bear
tension, resisting pulling forces within the cell.
• They form a 3-D network called the cortex just
inside the plasma membrane to help support
the cell’s shape.
• Bundles of microfilaments make up the core of
microvilli of intestinal cells.
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• Microfilaments that function in cellular motility
contain the protein myosin in addition to actin.
• In muscle cells, thousands of actin filaments
are arranged parallel to one another.
• Thicker filaments composed of myosin
interdigitate with the thinner actin fibers.
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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 cortical
cytoplasm (gel)
Chloroplast
Streaming
cytoplasm
(sol)
Parallel actin
filaments
(c)
Vacuole
Cell wall
Cytoplasmic streaming in plant cells
Sarcomere – muscle cell unit of contraction
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 cortical
cytoplasm (gel)
Chloroplast
Streaming
cytoplasm
(sol)
Vacuole
Parallel actin
filaments
(c) Cytoplasmic streaming in plant cells
Cell wall
• Localized contraction brought about by actin
and myosin also drives amoeboid movement.
• Pseudopodia (cellular extensions) extend and
contract through the reversible assembly and
contraction of actin subunits into
microfilaments.
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• Cytoplasmic streaming is a circular flow of
cytoplasm within cells.
• This streaming speeds distribution of materials
within the cell.
• In plant cells, actin-myosin interactions and solgel transformations drive cytoplasmic
streaming.
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Intermediate Filaments
• Intermediate filaments range in diameter from
8–12 nanometers, larger than microfilaments
but smaller than microtubules.
• They support cell shape and fix organelles in
place.
• Intermediate filaments are more permanent
cytoskeleton fixtures than the other two
classes.
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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
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Cell Walls of Plants
• The cell wall is an extracellular structure that
distinguishes plant cells from animal cells.
• Prokaryotes, fungi, and some protists also have
cell walls.
• The cell wall protects the plant cell, maintains its
shape, and prevents excessive uptake of water.
• Plant cell walls are made of cellulose fibers
embedded in other polysaccharides and protein.
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• Plant cell walls 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.
• Plasmodesmata are channels between
adjacent plant cells.
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Plant
cell walls
Secondary cell wall
Primary cell wall
outermost of the cell walls
Middle lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata
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
such as collagen, proteoglycans, and
fibronectin.
• ECM proteins bind to receptor proteins in the
plasma membrane called integrins.
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Extracellular matrix (ECM) of an animal cell
Collagen
Proteoglycan
complex
EXTRACELLULAR FLUID
Polysaccharide
molecule
Carbohydrates
Fibronectin
Core
protein
Integrins
Proteoglycan
molecule
Plasma
membrane
Proteoglycan complex
Microfilaments
CYTOPLASM
ECM of Animal cell
Collagen
Proteoglycan
complex
EXTRACELLULAR FLUID
Fibronectin
Integrins
Plasma
membrane
Microfilaments
CYTOPLASM
• Functions of the ECM:
– Support
– Adhesion
– Movement
– Regulation
– Identification “ID” cell-to-cell recognition
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Intercellular Junctions
• Neighboring cells in tissues, organs, or organ
systems often adhere, interact, and
communicate through direct physical contact
• Intercellular junctions facilitate this contact
• There are several types of intercellular junctions
– *Plasmodesmata = channels / plant cells
– *Gap junctions = channels / animal cells
– Tight junctions – waterproof
– Desmosomes - anchors
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Plasmodesmata in Plant Cells
• Plasmodesmata are channels that perforate
plant cell walls.
• Through plasmodesmata, water and small
solutes (and sometimes proteins and RNA) can
pass from cell to cell.
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Plasmodesmata between plant cells
Cell walls
Interior
of cell
Interior
of cell
0.5 µm
Plasmodesmata Plasma membranes
Tight Junctions, Desmosomes, and Gap Junctions in
Animal Cells
• At tight junctions, membranes of neighboring
cells are pressed together, preventing leakage of
extracellular fluid… waterproof.
• desmosomes (anchoring junctions) fasten cells
together into strong sheets.
• gap junctions (communicating junctions)
provide cytoplasmic channels between adjacent
cells.
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Intercellular junctions
in animal tissues
Tight junctions
Tight junction
prevent
fluid from moving
across a layer of cells
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
Gap
junctions
Space
between
cells
Plasma membranes
of adjacent cells
Desmosome
1 µm
Extracellular
matrix
Gap junction
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 © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The emergence of cellular functions –> Macrophages’s
ability to engulf and destroy bacteria
Cell Structures
& Functions
Cell Component
Concept 6.3
The eukaryotic cell’s genetic
instructions are housed in
the nucleus and carried out
by the ribosomes
Structure
Surrounded by nuclear
envelope (double membrane)
perforated by nuclear pores.
The nuclear envelope is
continuous with the
endoplasmic reticulum (ER).
Nucleus
Function
Houses chromosomes, made of
chromatin (DNA, the genetic
material, and proteins); contains
nucleoli, where ribosomal
subunits are made. Pores
regulate entry and exit of
materials.
(ER)
Two subunits made of riboProtein synthesis
somal RNA and proteins; can be
free in cytosol or bound to ER
Ribosome
Concept 6.4
The endomembrane system
regulates protein traffic and
performs metabolic functions
in the cell
Concept 6.5
Mitochondria and chloroplasts change energy from
one form to another
Extensive network of
membrane-bound tubules and
sacs; membrane separates
lumen from cytosol;
continuous with
the nuclear envelope.
Smooth ER: synthesis of
lipids, metabolism of carbohydrates, Ca2+ storage, detoxification of drugs and poisons
Golgi apparatus
Stacks of flattened
membranous
sacs; has polarity
(cis and trans
faces)
Modification of proteins, carbohydrates on proteins, and phospholipids; synthesis of many
polysaccharides; sorting of Golgi
products, which are then
released in vesicles.
Lysosome
Membranous sac of hydrolytic
enzymes (in animal cells)
Vacuole
Large membrane-bounded
vesicle in plants
Digestion, storage, waste
disposal, water balance, cell
growth, and protection
Mitochondrion
Bounded by double
membrane;
inner membrane has
infoldings (cristae)
Cellular respiration
Endoplasmic reticulum
(Nuclear
envelope)
Chloroplast
Peroxisome
Rough ER: Aids in synthesis of
secretory and other proteins from
bound ribosomes; adds
carbohydrates to glycoproteins;
produces new membrane
Breakdown of ingested substances,
cell macromolecules, and damaged
organelles for recycling
Typically two membranes
Photosynthesis
around fluid stroma, which
contains membranous thylakoids
stacked into grana (in plants)
Specialized metabolic
compartment bounded by a
single membrane
Contains enzymes that transfer
hydrogen to water, producing
hydrogen peroxide (H2O2) as a
by-product, which is converted
to water by other enzymes
in the peroxisome
Structure
Cell Component
Concept 6.3
Nucleus
The eukaryotic cell’s
Genetic Instructions
are housed in
the nucleus and
carried out
by the ribosomes
Function
Surrounded by nuclear
envelope (double membrane)
perforated by nuclear pores.
The nuclear envelope is
continuous with the
endoplasmic reticulum (ER).
Houses chromosomes, made of
chromatin (DNA, the genetic
material, and proteins); contains
nucleoli, where ribosomal
subunits are made. Pores
regulate entry and exit os
materials.
Two subunits made of ribosomal RNA and proteins; can be
free in cytosol or bound to ER
Protein synthesis
(ER
)
Ribosome
Cell Component
Concept 6.4
Structure
Extensive network of
membrane-bound tubules and
(Nuclear sacs; membrane separates
envelope)
lumen from cytosol;
continuous with
the nuclear envelope.
Smooth ER: synthesis of
lipids, metabolism of carbohydrates, Ca2+ storage, detoxification of drugs and poisons
Stacks of flattened
membranous
sacs; has polarity
(cis and trans
faces)
Modification of proteins, carbohydrates on proteins, and phospholipids; synthesis of many
polysaccharides; sorting of
Golgi products, which are then
released in vesicles.
Endoplasmic reticulum
The endomembrane
system
regulates protein
traffic and
performs metabolic
functions
in the cell
Golgi apparatus
Lysosome
Vacuole
Function
Rough ER: Aids in sythesis of
secretory and other proteins
from bound ribosomes; adds
carbohydrates to glycoproteins;
produces new membrane
Breakdown of ingested subMembranous sac of hydrolytic stances cell macromolecules,
enzymes (in animal cells)
and damaged organelles for
recycling
Large membrane-bounded
vesicle in plants
Digestion, storage, waste
disposal, water balance, cell
growth, and protection
Cell Component
Concept 6.5
Mitochondrion
Mitochondria and
chloroplasts change
energy from
one form to another
Structure
Bounded by double
membrane;
inner membrane has
infoldings (cristae)
Function
Cellular respiration
Chloroplast
Typically two membranes
around fluid stroma, which
contains membranous thylakoids
stacked into grana (in plants)
Photosynthesis
Peroxisome
Specialized metabolic
compartment bounded by a
single membrane
Contains enzymes that transfer
hydrogen to water, producing
hydrogen peroxide (H2O2) as a
by-product, which is converted
to water by other enzymes
in the peroxisome
You should now be able to:
1. Distinguish between the following pairs of
terms: magnification and resolution;
prokaryotic and eukaryotic cell; free and
bound ribosomes; smooth and rough ER.
2. Describe the structure and function of the
components of the endomembrane system.
3. Briefly explain the role of mitochondria,
chloroplasts, and peroxisomes.
4. Describe the functions of the cytoskeleton.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
5. Compare the structure and functions of
microtubules, microfilaments, and
intermediate filaments.
6. Explain how the ultrastructure of cilia and
flagella relate to their functions.
7. Describe the structure of a plant cell wall.
8. Describe the structure and roles of the
extracellular matrix in animal cells.
9. Describe four different intercellular junctions.
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings