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LECTURE PRESENTATIONS
For CAMPBELL BIOLOGY, NINTH EDITION
Jane B. Reece, Lisa A. Urry, Michael L. Cain, Steven A. Wasserman, Peter V. Minorsky, Robert B. Jackson
Chapter 6
A Tour of the Cell
Lectures by
Erin Barley
Kathleen Fitzpatrick
© 2011 Pearson Education, Inc.
Overview: The Fundamental Units of Life
• All organisms are made of cells
• Cell structure  function
• All cells are related by their descent from earlier
cells
© 2011 Pearson Education, Inc.
Microscopy
• Scientists use microscopes to visualize cells too
small to see with the naked eye
• In a light microscope (LM), visible light is
passed through a specimen and then through
glass lenses
• Lenses refract (bend) the light, so that the image
is magnified
© 2011 Pearson Education, Inc.
• Three important parameters of microscopy
– 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
© 2011 Pearson Education, Inc.
10 m
Human height
1m
0.1 m
Length of some
nerve and
muscle cells
Chicken egg
1 cm
Unaided eye
Frog egg
1 mm
Human egg
Most plant and
animal cells
10 m
1 m
100 nm
Nucleus
Most bacteria
Mitochondrion
Smallest bacteria
Viruses
Ribosomes
10 nm
Proteins
Lipids
1 nm
0.1 nm
Small molecules
Atoms
Superresolution
microscopy
Electron microscopy
100 m
Light microscopy
Figure 6.2
Figure 6.3
Light Microscopy (LM)
Electron Microscopy (EM)
Brightfield
(unstained specimen)
Confocal
Longitudinal section
of cilium
Cross section
of cilium
50 m
Cilia
50 m
Brightfield
(stained specimen)
2 m
2 m
Deconvolution
10 m
Phase-contrast
Differential-interferencecontrast (Nomarski)
Super-resolution
10 m
1 m
Fluorescence
Scanning electron
microscopy (SEM)
Transmission electron
microscopy (TEM)
• LMs can magnify effectively to about 1,000 times
the size of the actual specimen
• Stain/contrast techniques reveal detail
• Most subcellular structures, including
organelles (membrane-enclosed
compartments), are too small to see with light
microscope
© 2011 Pearson Education, Inc.
• Two kinds of electron microscopes (EMs)
1. Scanning electron microscopes (SEMs) look
at surface of a specimen, take 3-D photos
2. Transmission electron microscopes (TEMs)
focus a beam of electrons through a thin slice of
a specimen
– TEMs are used to study the internal structure of cells
© 2011 Pearson Education, Inc.
• light microscopy – more detail than in the past
– Confocal microscopy, deconvolution
• sharper images of 3-D tissues and cells
– New techniques for labeling cells improve
resolution
© 2011 Pearson Education, Inc.
Cell Fractionation
• Cell fractionation – taking
cells apart to look at the
organelles & study function
• Centrifuges separate
organelles by fractionate
• Biochemistry and cytology
help correlate cell function
with structure
© 2011 Pearson Education, Inc.
Concept 6.2: Eukaryotic cells have internal
membranes that compartmentalize their
functions
• two types:
1.
2.
prokaryotic (bacteria/Archaea)
eukaryotic (nucleus)
•
Protists, fungi, animals, and plants all consist of
eukaryotic cells
© 2011 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic
Cells
• Basic features of all cells
–
–
–
–
Plasma membrane
Semifluid substance called cytosol
Chromosomes (carry genes)
Ribosomes (make proteins)
© 2011 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic
Cells
• Many cell types have walls
–
–
–
–
Some bacteria (peptidoglycans)
Some fungi (chitin)
Some protists (silicon)
Most plants (cellulose)
– NOT ANIMALS (no wall)
© 2011 Pearson Education, Inc.
Comparing Prokaryotic and Eukaryotic
Cells
• Many cell types can do photosynthesis
– Some bacteria
– Some protists
– Almost ALL plants (exception: dodder)
– NOT ANIMALS or fungi (unless stolen organelle
or symbiont)
© 2011 Pearson Education, Inc.
• 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
© 2011 Pearson Education, Inc.
Figure 6.5
Fimbriae
Nucleoid
Ribosomes
Plasma
membrane
Bacterial
chromosome
Cell wall
Capsule
0.5 m
(a) A typical
rod-shaped
bacterium
Flagella
(b) A thin section
through the
bacterium Bacillus
coagulans (TEM)
• Eukaryotic cells have
– DNA in a nucleus (“nuclear envelope”)
– organelles
– Cytoplasm between the plasma membrane
and nucleus
• Eukaryotic cells are usually prokaryotic cells
© 2011 Pearson Education, Inc.
plasma membrane
• Semi-permeables: controls what gets in or out
of cell (oxygen, nutrients, waste)
• Mostly a double layer of phospholipids
• Other parts of membrane include Lots of other
proteins and carbohydrates
© 2011 Pearson Education, Inc.
Figure 6.6
Outside of cell
Inside of cell
0.1 m
(a) TEM of a plasma
membrane
Carbohydrate side chains
Hydrophilic
region
Hydrophobic
region
Hydrophilic
region
Phospholipid
Proteins
(b) Structure of the plasma membrane
• Why cells don’t get too big:
• They need enough surface area to exchange
oxygen/waste/nutrients
• Small cells have a greater surface area relative
to volume
© 2011 Pearson Education, Inc.
A Panoramic View of the Eukaryotic Cell
• A eukaryotic cell: membrane-bound organelles
• Plant and animal cells have most of the same
organelles
BioFlix: Tour of an Animal Cell
BioFlix: Tour of a Plant Cell
© 2011 Pearson Education, Inc.
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
• Chef cartoon!
© 2011 Pearson Education, Inc.
The Nucleus: Information Central
• The nucleus contains most of the cell’s genes
and is usually the most conspicuous organelle
• Mitochondria have own DNA and ribosomes
• The nuclear envelope around nucleus
• a double membrane; each membrane consists
of a lipid bilayer
© 2011 Pearson Education, Inc.
Figure 6.9
1 m
Nucleus
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Rough ER
Surface of nuclear
envelope
Pore
complex
Ribosome
Chromatin
1 m
0.25 m
Close-up
of nuclear
envelope
Pore complexes (TEM)
Nuclear lamina (TEM)
Nuclear Pores (windows on the castle)
• 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
• Proteins control membrane shape (true of many
membranes, not just this one)
© 2011 Pearson Education, Inc.
• DNA = deoxyribonucleic acid
• Chromatin = DNA wrapped
around histone proteins
• Chromosomes = long chain
of chromatin
(one long DNA molecule and the histone
proteins it is wrapped around)
Looks like this @ cell division 
spread out the rest of time
© 2011 Pearson Education, Inc.
nucleolus
• Part of the nucleus
• Where we make rRNA
– Major part of ribosome (chef)
All RNA is made in the nucleus
Reading DNA to make RNA is called “transcription”
(monk-like “scribe”)
© 2011 Pearson Education, Inc.
Ribosomes: Chef that makes Proteins
• Part rRNA, part protein
• Found in two places in cell
– In the cytosol (free ribosomes)
Floating between nucleus and plasma memb.
– Stuck to endoplasmic reticulum or nuclear
envelope (bound ribosomes)
May be able to move in or out of ER
© 2011 Pearson Education, Inc.
Figure 6.10
0.25 m
Free ribosomes in cytosol
Endoplasmic reticulum (ER)
Ribosomes bound to ER
Large
subunit
TEM showing ER and
ribosomes
Small
subunit
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
© 2011 Pearson Education, Inc.
The Endoplasmic Reticulum: Biosynthetic
Factory
• ER >50% of membranes in eukaryotic cells
• continuous with the nuclear envelope
• There are two distinct regions of ER
– Smooth ER, no ribosomes
– Rough ER, covered in ribosomes
© 2011 Pearson Education, Inc.
Functions of Smooth ER
• The smooth ER
–
–
–
–
makes lipids
Metabolizes carbohydrates
Detoxifies drugs and poisons
Stores calcium ions
• “sarcoplasmic reticulum”
© 2011 Pearson Education, Inc.
Functions of Rough ER
• The rough ER
– bound ribosomes
• Make glycoproteins (proteins + carb)
– Gives off transport vesicles, proteins
surrounded by membranes
– Is a membrane factory for the cell
© 2011 Pearson Education, Inc.
Golgi Apparatus: Shipping & Receiving Center
Golgi apparatus: membranous sacs (cisternae)
• Functions of the Golgi apparatus
– Modifies ER products
– Sorts & packages stuff into transport vesicles
– Makes some macromolecules
© 2011 Pearson Education, Inc.
Lysosomes: Digestive Compartments
• Cell’s mobile stomach unit
• Lysosome: membranous sac full of
hydrolytic enzymes (work best in acid)
– digests macromolecules
•
•
•
•
Proteins
Fats
Polysaccharides
nucleic acids
Animation: Lysosome Formation
© 2011 Pearson Education, Inc.
• Some types of cell can eat another cell by
phagocytosis; this forms a food vacuole
• A lysosome fuses with the food vacuole and
digests the molecules (breaks it apart)
• Lysosomes also do “autophagy” (self eating)
– Break down cell’s own old or unneeded organelles
and macromolecules,
– Can reuse parts
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Vacuoles: Maintenance Compartments
• In plant cell or fungal cell
• can have one or several vacuoles
• derived from ER and Golgi apparatus
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• Food vacuoles are formed by phagocytosis
• Contractile vacuoles, found in many freshwater
protists, pump excess water out of cells
– Water wants to dilute stuff, often flowing into cells
– Must pump extra out
• Central vacuoles, found in many mature plant
cells, hold organic compounds and water
Video: Paramecium Vacuole
© 2011 Pearson Education, Inc.
The Endomembrane System: A Review
• The endomembrane system is a complex and
dynamic player in the cell’s compartmental
organization
© 2011 Pearson Education, Inc.
Concept 6.5: Mitochondria and chloroplasts
change energy from one form to another
• Mitochondria: where respiration happens
• Uses sugar and oxygen to make ATP
Found in ALL eukaryotes
• Chloroplasts: where photosynthesis happens
– found in plants and some protists (algae)
– Not found in animals or fungi
no photosynthesis unless symbiosis or theft
© 2011 Pearson Education, Inc.
Weird Stuff
• Prokaryotes don’t have chloroplasts
• No membrane bound organelles
• Some still do photosynthesis
• Peroxisomes are oxidative organelles
© 2011 Pearson Education, Inc.
Evolutionary Origins: Mitochondria & Chloroplasts
• Similar to bacteria
– free ribosomes and circular DNA molecules
– Can grow & reproduce independently in cells
• Enveloped by a double membrane
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• The Endosymbiont theory
– An early ancestor of eukaryotic cells engulfed
a nonphotosynthetic prokaryotic cell, which
formed an endosymbiont relationship with its
host
– The host cell and endosymbiont merged into
a single organism, a eukaryotic cell with a
mitochondrion
– At least one of these cells may have taken up
a photosynthetic prokaryote, becoming the
ancestor of cells that contain chloroplasts
© 2011 Pearson Education, Inc.
Figure 6.16
Endoplasmic
reticulum
Nucleus
Engulfing of oxygenNuclear
using nonphotosynthetic envelope
prokaryote, which
becomes a mitochondrion
Ancestor of
eukaryotic cells
(host cell)
Mitochondrion
Nonphotosynthetic
eukaryote
At least
one cell
Engulfing of
photosynthetic
prokaryote
Chloroplast
Mitochondrion
Photosynthetic eukaryote
Mitochondria: Chemical Energy Conversion
• Mitochondria in nearly all eukaryotic cells
• smooth outer membrane & inner membrane
folded into cristae
• two compartments:
– intermembrane space
•
H+ pumped to here
– mitochondrial matrix
•
H+ flows passively to here
© 2011 Pearson Education, Inc.
Mitochondria: Chemical Energy Conversion
• 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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Chloroplasts: Capture of Light Energy
• Chloroplasts have chlorophyll
• found in
– Leaves
– other green organs of plants
– algae
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• Chloroplast structure includes
– Thylakoids, membrane sacs (hydrogen ions)
– Granum: stacks of thylakoids
– Stroma, fluid filled space around thylakoids
• The chloroplast is one of a group of plant
organelles, called plastids
© 2011 Pearson Education, Inc.
Peroxisomes: Oxidation
•
•
•
•
specialized metabolic compartments
single membrane
Make hydrogen peroxide & convert to water
Peroxisomes perform reactions with many
different functions
• How peroxisomes are related to other organelles
is still unknown
© 2011 Pearson Education, Inc.
Concept 6.6: cytoskeleton - protein fibers to
organize structures and activities in the cell
•
•
•
•
fibers extend throughout cytoplasm
Organizes cell’s structures and activities
anchors many organelles
three types
– Microtubules
– Intermediate filaments
– Microfilaments
© 2011 Pearson Education, Inc.
10 m
Figure 6.20
Cytoskeleton job: Support and Motility
• Supports cell and maintains shape
• Interacts with motor proteins to produce motility
• vesicles can travel along microtubules
• Recent evidence suggests that the cytoskeleton
may help regulate biochemical activities
© 2011 Pearson Education, Inc.
Components of the Cytoskeleton
• Three main types of fibers
– Microtubules: thickest
– Intermediate filaments are fibers with
diameters in a middle range
– Microfilaments: thinnest
© 2011 Pearson Education, Inc.
Table 6.1
10 m
10 m
5 m
Column of tubulin dimers
Keratin proteins
Fibrous subunit (keratins
coiled together)
Actin subunit
25 nm
7 nm


Tubulin dimer
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
© 2011 Pearson Education, Inc.
Centrosomes and Centrioles
• The centrosome is a “microtubule-organizing
center”
• In many cells, microtubules grow out from a
centrosome near the nucleus
• In animal cells, the centrosome has a pair of
centrioles, each with nine triplets of
microtubules arranged in a ring
© 2011 Pearson Education, Inc.
Figure 6.22
Centrosome
Microtubule
Centrioles
0.25 m
Longitudinal
section of
one centriole
Microtubules
Cross section
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
Video: Chlamydomonas
Video: Paramecium Cilia
© 2011 Pearson Education, Inc.
• Cilia and flagella share a common structure
– microtubules sheathed by plasma membrane
– basal body to anchor the cilium or flagellum
– Dynein: motor protein that bends cilia/flagella
Animation: Cilia and Flagella
© 2011 Pearson Education, Inc.
• How dynein “walking” moves flagella and cilia
− 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
© 2011 Pearson Education, Inc.
Microfilaments (Actin Filaments)
• Microfilaments:twisted double chain of actin
• resist pulling forces within the cell
• Cortex: 3-D network inside plasma membrane
support the cell’s shape
© 2011 Pearson Education, Inc.
Microfilaments (Actin Filaments)
• Bundles of microfilaments make up the core of
microvilli of intestinal cells
© 2011 Pearson Education, Inc.
• Microfilaments: part of muscle contraction
• Actin fibers pulled on by myosin fibers
© 2011 Pearson Education, Inc.
• 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
© 2011 Pearson Education, Inc.
• 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
Video: Cytoplasmic Streaming
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
• 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
© 2011 Pearson Education, Inc.
Figure 6.28
Secondary
cell wall
Primary
cell wall
Middle
lamella
1 m
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
© 2011 Pearson Education, Inc.
Figure 6.30
Collagen
Polysaccharide
molecule
EXTRACELLULAR FLUID
Proteoglycan
complex
Fibronectin
Carbohydrates
Core
protein
Integrins
Proteoglycan
molecule
Plasma
membrane
Proteoglycan complex
Microfilaments
CYTOPLASM
• Functions of the ECM
–
–
–
–
Support
Adhesion
Movement
Regulation
© 2011 Pearson Education, Inc.
Cell 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
© 2011 Pearson Education, Inc.
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
© 2011 Pearson Education, Inc.
Figure 6.31
Cell walls
Interior
of cell
Interior
of cell
0.5 m
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
• Desmosomes (anchoring junctions) fasten cells
together into strong sheets
• Gap junctions (communicating junctions) provide
cytoplasmic channels between adjacent cells
© 2011 Pearson Education, Inc.
Animation: Tight Junctions
Animation: Desmosomes
Animation: Gap Junctions
© 2011 Pearson Education, Inc.
Figure 6.32
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
TEM
0.5 m
Tight junction
Intermediate
filaments
Desmosome
TEM
1 m
Gap
junction
Space
between cells
Plasma membranes
of adjacent cells
Extracellular
matrix
TEM
Ions or small
molecules
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
© 2011 Pearson Education, Inc.
5 m
Figure 6.33
Figure 6.UN01
Nucleus
(ER)
(Nuclear
envelope)
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