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Cells
Rough
endoplasmic
reticulum
Smooth endoplasmic
reticulum
Nucleus
Flagellum
Not in most
plant cells
Lysosome
Ribosomes
Centriole
Peroxisome
Microtubule
Cytoskeleton
Intermediate
filament
Microfilament
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
Golgi
apparatus
Plasma membrane
Mitochondrion
The Art of Looking at Cells
• Early scientists who observed cells
– Made detailed sketches of what they saw
Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings
• These early sketches revealed an important
relationship
– Between art and biology, the most visual of the
sciences
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INTRODUCTION TO THE CELL
4.1 Microscopes provide windows to the world of the cell
• The light microscope (LM)
– Enables us to see the overall shape and structure
of a cell
Eyepiece
Ocular
lens
Objective lens
Specimen
Condenser
lens
Light
source
Figure 4.1A
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• Light microscopes
Figure 4.1B
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LM 1,000
– Magnify cells, living and preserved, up to
1,000 times
• The electron microscope
Figure 4.1C
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TEM 2,800 
SEM 2,000 
– Allows greater magnification and reveals
cellular details
Figure 4.1D
• Different types of light microscopes
220
1,000
– Use different techniques to enhance contrast
and selectively highlight cellular components
Figure 4.1E
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Figure 4.1F
4.2 Most cells are microscopic
• Cells vary in size and shape
10 m
100 mm
(10 cm)
Length of some
nerve and
muscle cells
Chicken egg
Unaided eye
Human height
1m
10 mm
(1 cm)
Frog egg
100 m
Most plant and
animal cells
10 m
Nucleus
Light microscope
1 mm
Most bacteria
100 nm
Mitochondrion
Mycoplasmas
(smallest bacteria)
Viruses
Ribosome
10 nm
Proteins
Lipids
1 nm
Small molecules
Figure 4.2A
0.1 nm
Atoms
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Electron microscope
1 m
• The microscopic size of most cells ensures a
sufficient surface area
– Across which nutrients and wastes can
move to service the cell volume
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• A small cell has a greater ratio of surface area
to volume
– Than a large cell of the same shape
10 m
30 m
30 m
Figure 4.2B
Surface area
of one large cube
 5,400 m2
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10 m
Total surface area
of 27 small cubes
 16,200 m2
4.3 Prokaryotic cells are structurally simpler than
eukaryotic cells
• There are two kinds of cells
Colorized TEM 15,000 
– Prokaryotic and eukaryotic
Prokaryotic cell
Nucleoid
region
Nucleus
Figure 4.3A
Eukaryotic cell
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rganelles
• Prokaryotic cells are small, relatively simple cells
– That do not have a membrane-bound nucleus
Prokaryotic
flagella
Ribosomes
Capsule
Cell wall
Plasma
membrane
Nucleoid region (DNA)
Pili
Figure 4.3B
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4.4 Eukaryotic cells are partitioned into functional
compartments
• All other forms of life are composed of more
complex eukaryotic cells
– Distinguished by the presence of a true
nucleus
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• Membranes form the boundaries of many
eukaryotic cells
– Compartmentalizing the interior of the cell
and facilitating a variety of metabolic
activities
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• A typical animal cell
– Contains a variety of membranous organelles
Rough
endoplasmic
reticulum
Smooth endoplasmic
reticulum
Nucleus
Flagellum
Not in most
plant cells
Lysosome
Ribosomes
Centriole
Peroxisome
Microtubule
Cytoskeleton
Figure 4.4A
Intermediate
filament
Microfilament
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Golgi
apparatus
Plasma membrane
Mitochondrion
• A typical plant cell has some structures that an
animal cell lacks
– Such as chloroplasts and a rigid cell wall
Nucleus
Rough
endoplasmic
reticulum
Ribosomes
Golgi
apparatus
Not in
animal
cells
Central
vacuole
Chloroplast
Cell wall
Mitochondrion
Peroxisome
Plasma membrane
Figure 4.4B
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Smooth
endoplasmic
reticulum
Microtubule
Intermediate
filament
Microfilament
Cytoskeleton
ORGANELLES OF THE ENDOMEMBRANE SYSTEM
4.5 The nucleus is the cell’s genetic control
center
• The largest organelle is usually the nucleus
– Which is separated from the cytoplasm by
the nuclear envelope
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• The nucleus is the cellular control center
– Containing the cell’s DNA, which directs
cellular activities
Chromatin
Nucleolus
Nucleus
Two membranes
of nuclear
envelope
Pore
Rough
endoplasmic
reticulum
Figure 4.5
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Ribosomes
4.6 Overview: Many cell organelles are
connected through the endomembrane system
• The endomembrane system is a collection of
membranous organelles
– That manufactures and distributes cell
products
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4.7 Smooth endoplasmic reticulum has a variety of functions
• Smooth endoplasmic reticulum, or smooth ER
– Synthesizes lipids
– Processes toxins and drugs in liver cells
– Stores and releases calcium ions in muscle cells
Smooth ER
Rough ER
Nuclear
envelope
Figure 4.7
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Ribosomes
Rough ER
TEM 45,000
Smooth ER
4.8 Rough endoplasmic reticulum makes
membrane and proteins
• The rough ER
– Manufactures membranes
Smooth ER
Rough ER
Nuclear
envelope
Figure 4.7
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Ribosomes
Rough ER
TEM 45,000
Smooth ER
• Ribosomes on the surface of the rough ER
– Produce proteins that are secreted,
inserted into membranes, or transported in
vesicles to other organelles
Transport vesicle
buds off
4
Ribosome
3
Secretory
(glyco-) protein
inside transport vesicle
Sugar chain
1
2
Glycoprotein
Polypeptide
Rough ER
Figure 4.8
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4.9 The Golgi apparatus finishes, sorts, and ships
cell products
• Stacks of membranous sacs receive and modify
ER products
– Then ship them to other organelles or the cell
surface
Golgi apparatus
Golgi
apparatus
Transport
vesicle
from ER
New vesicle
forming
Figure 4.9
“Shipping” side
of Golgi apparatus
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Transport
vesicle from
the Golgi
TEM 130,000
“Receiving” side of
Golgi apparatus
4.10 Lysosomes are digestive compartments
within a cell
• Lysosomes are sacs of enzymes
– That function in digestion within a cell
Rough ER
1
Transport vesicle
(containing inactive
hydrolytic enzymes)
Golgi
apparatus
Plasma
membrane
Engulfment
of particle
Lysosome
engulfing
damaged
organelle
2
“Food”
Lysosomes
3
5
Food
vacuole
Figure 4.10A
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4
Digestion
• Lysosomes in white blood cells
– Destroy bacteria that have been ingested
Lysosome
Figure 4.10B
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TEM 8,500
Nucleus
• Lysosomes also recycle damaged organelles
Lysosome containing
two damaged organelles
Peroxisome fragment
Figure 4.10C
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TEM 42,500
Mitochondrion fragment
CONNECTION
4.11 Abnormal lysosomes can cause fatal
diseases
• Lysosomal storage diseases
– Interfere with various cellular functions
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4.12 Vacuoles function in the general
maintenance of the cell
• Plant cells contain a large central vacuole,
– Which has lysosomal and storage functions
Nucleus
Chloroplast
Figure 4.12A
Colorized TEM 8,700
Central
vacuole
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• Some protists have contractile vacuoles
– That pump out excess water
Contractile
vacuoles
Figure 4.12B
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LM 650
Nucleus
4.13 A review of the endomembrane system
• The various organelles of the endomembrane system
– Are interconnected structurally and functionally
Rough ER
Transport vesicle
from ER to Golgi
Transport vesicle from
Golgi to plasma membrane
Plasma
membrane
Nucleus
Vacuole
Lysosome
Figure 4.13
Smooth ER
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Nuclear envelope
Golgi apparatus
ENERGY-CONVERTING ORGANELLES
4.14 Chloroplasts convert solar energy to chemical
energy
• Chloroplasts, found in plants and some protists
– Convert solar energy to chemical energy in
sugars
Chloroplast
Inner and outer
membranes
Granum
Intermembrane
space
Figure 4.14
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TEM 9,750
Stroma
4.15 Mitochondria harvest chemical energy from food
• Mitochondria carry out cellular respiration
– Which uses the chemical energy in food to
make ATP for cellular work
Mitochondrion
Outer
membrane
Inner
membrane
Cristae
Figure 4.15
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Matrix
TEM 44,880
Intermembrane
space
THE CYTOSKELETON AND RELATED STRUCTURES
4.16 The cell’s internal skeleton helps organize
its structure and activities
• A network of protein fibers
– Make up the cytoskeleton.
Tubulin subunit
Actin subunit
Fibrous subunits
7 nm
Microfilament
Figure 4.16
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25 nm
10 nm
Intermediate filament
Microtubule
• Microfilaments of actin
– Enable cells to change shape and move
• Intermediate filaments
– Reinforce the cell and anchor certain
organelles
• Microtubules give the cell rigidity
– And provide anchors for organelles and act
as tracks for organelle movement
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4.17 Cilia and flagella move when microtubules bend
• Eukaryotic cilia and flagella
Figure 4.17A
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LM 600
Colorized SEM 4,100
– Are locomotor appendages that protrude from
certain cells
Figure 4.17B
• Clusters of microtubules
– Drive the whipping action of these organelles
Flagellum
Electron micrographs
of cross sections:
Outer microtubule
doublet
TEM 206,500
Central
microtubules
Radial spoke
Dynein arms
Flagellum
Figure 4.17C
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Basal body
(structurally identical to
centriole)
TEM 206,500
Plasma
membrane
Basal body
CELL SURFACES AND JUNCTIONS
4.19 Cell surfaces protect, support, and join cells
• Cells interact with their environments and each
other via their surfaces.
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• Plant cells
– Are supported by rigid cell walls made largely
of cellulose
– Connect by plasmodesmata, which are
connecting channels
Walls of two
adjacent plant
cells
Vacuole
Plasmodesmata
Layers of one
plant cell wall
Cytoplasm
Plasma membrane
Figure 4.18A
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• Animal cells are embedded in an extracellular
matrix
– Which binds cells together in tissues
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• Tight junctions can bind cells together into
leakproof sheets
• Anchoring junctions link animal cells into strong
tissues
• Gap junctions allow substances to flow from cell to
cell
Tight junctions
Anchoring junction
Gap junctions
Figure 4.18B
Extracellular matrix
Space between cells
Plasma membranes of adjacent cells
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FUNCTIONAL CATEGORIES OF ORGANELLES
4.19 Eukaryotic organelles comprise four
functional categories
• Eukaryotic organelles fall into four functional
groups
– Manufacturing
– Breakdown
– Energy processing
– Support, movement, and communication
between cells
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• Eukaryotic organelles and their functions
Table 4.19
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