6
A Chapter 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
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 6.2: Eukaryotic cells have internal
membranes that compartmentalize their functions
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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1
Comparing Prokaryotic and Eukaryotic Cells
Basic features of all cells:
Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-7
Outside of cell
Inside of
cell
0.1 m
(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
Small cells have a greater surface area relative
to volume
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3
Fig. 6-8
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
A Panoramic View of the Eukaryotic Cell
A eukaryotic cell has internal membranes that
partition the cell into organelles
Plant and animal cells have most of the same
organelles
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-9a
ENDOPLASMIC RETICULUM (ER)
Flagellum
Rough ER
Smooth ER
Nuclear
envelope
Nucleolus
NUCLEUS
Chromatin
Centrosome
Plasma
membrane
CYTOSKELETON:
Microfilaments
Intermediate
filaments
Microtubules
Ribosomes
Microvilli
Golgi
apparatus
Peroxisome
Mitochondrion
Lysosome
4
Fig. 6-9b
Nuclear envelope
NUCLEUS
Nucleolus
Chromatin
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Ribosomes
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
CYTOSKELETON
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
Cell wall
Plasmodesmata
Wall of adjacent cell
Concept 6.3: The eukaryotic cell s genetic
instructions are housed in the nucleus and carried
out by the ribosomes
The nucleus contains most of the DNA in a
eukaryotic cell
Ribosomes use the information from the DNA
to make proteins
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
The Nucleus: Information Central
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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5
Fig. 6-10
Nucleus
1 m
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Surface of
nuclear envelope
Rough ER
Ribosome
1 m
0.25 m
Close-up of nuclear
envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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)
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6
Fig. 6-11
Cytosol
Endoplasmic reticulum (ER)
Free ribosomes
Bound ribosomes
Large
subunit
Small
subunit
0.5 m
TEM showing ER and ribosomes
Diagram of a ribosome
Concept 6.4: The endomembrane system regulates
protein traffic and performs metabolic functions in
the cell
Components of the endomembrane system:
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
These components are either continuous or
connected via transfer by vesicles
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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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Fig. 6-12
Smooth ER
Nuclear
envelope
Rough ER
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
Transitional ER
Rough ER
200 nm
Functions of Smooth ER
The smooth ER
Synthesizes lipids
Metabolizes carbohydrates
Detoxifies poison
Stores calcium
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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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8
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-13
cis face
( receiving side of
Golgi apparatus)
0.1 m
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
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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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-14
Nucleus
1 m
Vesicle containing
two damaged organelles
1 m
Mitochondrion
fragment
Peroxisome
fragment
Lysosome
Digestive
enzymes
Lysosome
Plasma
membrane
Lysosome
Peroxisome
Digestion
Food vacuole
Vesicle
(a) Phagocytosis
Mitochondrion
Digestion
(b) Autophagy
Vacuoles: Diverse Maintenance Compartments
A plant cell or fungal cell may have one or
several vacuoles
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10
Food vacuoles are formed by phagocytosis
Contractile vacuoles, found in many
freshwater protists, pump excess water out of
cells
Central vacuoles, found in many mature plant
cells, hold organic compounds and water
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-15
Central vacuole
Cytosol
Nucleus
Central
vacuole
Cell wall
Chloroplast
5 m
The Endomembrane System: A Review
The endomembrane system is a complex and
dynamic player in the cell s compartmental
organization
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11
Concept 6.5: Mitochondria and chloroplasts
change energy from one form to another
Mitochondria are the sites of cellular
respiration, a metabolic process that generates
ATP
Chloroplasts, found in plants and algae, are
the sites of photosynthesis
Peroxisomes are oxidative organelles
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Mitochondria and chloroplasts
Are not part of the endomembrane system
Have a double membrane
Have proteins made by free ribosomes
Contain own their DNA
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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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12
Fig. 6-17
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
Inner
membrane
Cristae
Matrix
0.1 m
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
Chloroplasts are found in leaves and other
green organs of plants and in algae
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Chloroplast structure includes:
Thylakoids, membranous sacs, stacked to
form a granum
Stroma, the internal fluid
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13
Fig. 6-18
Ribosomes
Stroma
Inner and outer
membranes
Granum
Thylakoid
1 m
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 6.6: 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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14
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-21
Vesicle
ATP
(a)
Receptor for
motor protein
Motor protein Microtubule
(ATP powered)
of cytoskeleton
Microtubule
Vesicles
0.25 m
(b)
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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15
Centrosomes and Centrioles
In many cells, microtubules grow out from a
centrosome near the nucleus
The centrosome is a microtubule-organizing
center
In animal cells, the centrosome has a pair of
centrioles, each with nine triplets of
microtubules arranged in a ring
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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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Fig. 6-23
Direction of swimming
(a) Motion of flagella
5 m
Direction of organism s movement
Power stroke Recovery stroke
(b) Motion of cilia
15 m
16
Intermediate Filaments
Intermediate filaments range in diameter from
812 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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Concept 6.7: 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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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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17
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-30
Collagen
Proteoglycan
complex
EXTRACELLULAR FLUID
Polysaccharide
molecule
Carbohydrates
Fibronectin
Core
protein
Integrins
Proteoglycan
molecule
Plasma
membrane
Proteoglycan complex
Microfilaments
CYTOPLASM
Functions of the ECM:
Support
Adhesion
Movement
Regulation
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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
Tight junctions
Desmosomes
Gap junctions
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
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
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-28
Secondary
cell wall
Primary
cell wall
Middle
lamella
1 m
Central vacuole
Cytosol
Plasma membrane
Plant cell walls
Plasmodesmata
19
Tight Junctions, Desmosomes, and Gap Junctions in
Animal Cells
At tight junctions, membranes of neighboring
cells are pressed together, preventing leakage of
extracellular fluid
Desmosomes (anchoring junctions) fasten cells
together into strong sheets
Gap junctions (communicating junctions) provide
cytoplasmic channels between adjacent cells
Copyright 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 6-32
Tight junction
Tight junctions prevent
fluid from moving
across a layer of cells
0.5 m
Tight junction
Intermediate
filaments
Desmosome
Desmosome
Gap
junctions
Space
between
cells
Plasma membranes
of adjacent cells
1 m
Extracellular
matrix
Gap junction
0.1 m
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
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20
Fig. 6-UN1
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
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
Concept 6.4
The endomembrane system
regulates protein traffic and
performs metabolic functions
in the cell
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
(Nuclear
envelope)
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
Lysosome
Concept 6.5
Mitochondria and chloroplasts change energy from
one form to another
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
Chloroplast
Peroxisome
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
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