Download AP Biology Unit 3 Introductory PP

Chapter 26
The Tree of Life:
An Introduction to
Biological Diversity
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Overview: Changing Life on a Changing Earth
• Life is a continuum extending from the earliest
organisms to the variety of species that exist today
• Geological events change the course of evolution
• Conversely, life changes the planet that it inhabits
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Geologic history and biological history have been
episodic, marked by revolutions that opened many
new ways of life
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 26.1: Conditions on early Earth made the
origin of life possible
• Chemical and physical processes on early Earth
may have produced very simple cells through a
sequence of stages:
1. Abiotic synthesis of small organic molecules
2. Joining of these small molecules into polymers
3. Packaging of molecules into “protobionts”
4. Origin of self-replicating molecules
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 26-2
CH4
Water vapor
Electrode
Condenser
Cold
water
H2O
Cooled water
containing
organic
molecules
Sample for
chemical analysis
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Protobionts
• Protobionts are aggregates of abiotically produced
molecules surrounded by a membrane or
membrane-like structure
• Experiments demonstrate that protobionts could
have formed spontaneously from abiotically
produced organic compounds
• For example, small membrane-bounded droplets
called liposomes can form when lipids or other
organic molecules are added to water
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The “RNA World” and the Dawn of Natural Selection
• The first genetic material was probably RNA, not
DNA
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Early protobionts with self-replicating, catalytic
RNA would have been more effective at using
resources and would have increased in number
through natural selection
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The geologic record is divided into three eons: the
Archaean, the Proterozoic, and the Phanerozoic
• The Phanerozoic eon is divided into three eras:
the Paleozoic, Mesozoic, and Cenozoic
• Each era is a distinct age in the history of Earth
and its life, with boundaries marked by mass
extinctions seen in the fossil record
• Lesser extinctions mark boundaries of many
periods within each era
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Mass Extinctions
• The fossil record chronicles a number of
occasions when global environmental changes
were so rapid and disruptive that a majority of
species were swept away
Animation: The Geologic Record
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 26-8
600
Millions of years ago
400
300
200
500
100
0
100
2,500
80
Number of
taxonomic
families
Permian mass
extinction
2,000
Extinction rate
60
1,500
40
Cretaceous
mass extinction
20
1,000
Paleozoic
Mesozoic
Cenozoic
Neogene
Paleogene
Cretaceous
Jurassic
Triassic
0
Permian
Devonian
Silurian
Ordovician
Cambrian
Proterozoic eon
0
Carboniferous
500
• The Permian extinction killed about 96% of marine
animal species and 8 out of 27 orders of insects
• It may have been caused by volcanic eruptions
• The Cretaceous extinction doomed many marine
and terrestrial organisms, notably the dinosaurs
• It may have been caused by a large meteor
impact
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 26-9
NORTH
AMERICA
Yucatán
Peninsula
Chicxulub
crater
• Mass extinctions provided life with unparalleled
opportunities for adaptive radiations into newly
vacated ecological niches
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 26-10
Cenozoic
Humans
Land plants
Animals
Origin of solar
system and
Earth
1
4
Proterozoic
Eon
Multicellular
eukaryotes
Archaean
Eon
Billions of years ago
2
3
Prokaryotes
Single-celled
eukaryotes
Atmospheric
oxygen
The First Prokaryotes
• Prokaryotes were Earth’s sole inhabitants from 3.5
to about 2 billion years ago
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Photosynthesis and the Oxygen Revolution
• The earliest types of photosynthesis did not
produce oxygen
• Oxygenic photosynthesis probably evolved about
3.5 billion years ago in cyanobacteria
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 26.4: Eukaryotic cells arose from symbioses
and genetic exchanges between prokaryotes
• Among the most fundamental questions in biology
is how complex eukaryotic cells evolved from
much simpler prokaryotic cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Endosymbiotic Origin of Mitochondria and Plastids
• The theory of endosymbiosis proposes that
mitochondria and plastids were formerly small
prokaryotes living within larger host cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• The prokaryotic ancestors of mitochondria and
plastids probably gained entry to the host cell as
undigested prey or internal parasites
• In the process of becoming more interdependent,
the host and endosymbionts would have become
a single organism
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 26-13
Cytoplasm
DNA
Plasma
membrane
Ancestral
prokaryote
Infolding of
plasma membrane
Endoplasmic reticulum
Nuclear envelope
Nucleus
Engulfing of aerobic
heterotrophic
prokaryote
Cell with nucleus
and endomembrane
system
Mitochondrion
Mitochondrion
Ancestral
heterotrophic
eukaryote
Engulfing of
photosynthetic
prokaryote in
some cells
Plastid
Ancestral
photosynthetic eukaryote
• Key evidence supporting an endosymbiotic origin
of mitochondria and plastids:
– Similarities in inner membrane structures and
functions
– Both have their own circular DNA
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Eukaryotic Cells as Genetic Chimeras
• Endosymbiotic events and horizontal gene
transfers may have contributed to the large
genomes and complex cellular structures of
eukaryotic cells
• Eukaryotic flagella and cilia may have evolved
from symbiotic bacteria, based on symbiotic
relationships between some bacteria and
protozoans
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 26.5: Multicellularity evolved several
times in eukaryotes
• After the first eukaryotes evolved, a great range of
unicellular forms evolved
• Multicellular forms evolved also
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The Earliest Multicellular Eukaryotes
• Molecular clocks date the common ancestor of
multicellular eukaryotes to 1.5 billion years
• The oldest known fossils of eukaryotes are of
relatively small algae that lived about 1.2 billion
years ago
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• Some cells in the colonies became specialized for
different functions
• The first cellular specializations had already
appeared in the prokaryotic world
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Continental Drift
• The continents drift across our planet’s surface on
great plates of crust that float on the hot
underlying mantle
• These plates often slide along the boundary of
other plates, pulling apart or pushing each other
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 26-18
Eurasian Plate
North
American
Plate
Juan de Fuca
Plate
Philippine
Plate
Caribbean
Plate
Arabian
Plate
Indian
Plate
Cocos Plate
Pacific
Plate
Nazca
Plate
South
American
Plate
Scotia Plate
African
Plate
Antarctic
Plate
Australian
Plate
LE 26-19
Volcanoes and
volcanic islands
Trench
Oceanic ridge
• The formation of the supercontinent Pangaea
during the late Paleozoic era and its breakup
during the Mesozoic era explain many
biogeographic puzzles
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 26-20
Cenozoic
0
By the end of the
Mesozoic, Laurasia
and Gondwana
separated into the
present-day continents.
65.5
Mesozoic
135
251
Paleozoic
Millions of years ago
By about 10 million years
ago, Earth’s youngest
major mountain range,
the Himalayas, formed
as a result of India’s
collision with Eurasia
during the Cenozoic.
The continents continue
to drift today.
By the mid-Mesozoic
Pangaea split into
northern (Laurasia)
and southern
(Gondwana)
landmasses.
At the end of the
Paleozoic, all of
Earth’s landmasses
were joined in the
supercontinent
Pangaea.
Concept 26.6: New information has revised our
understanding of the tree of life
• Molecular data have provided insights into the
deepest branches of the tree of life
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Reconstructing the Tree of Life: A Work in Progress
• The five kingdom system has been replaced by
three domains: Archaea, Bacteria, and Eukarya
• Each domain has been split into kingdoms
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Domain Archaea
Domain Bacteria
Universal ancestor
Domain Eukarya
Charophyceans
Chlorophytes
Red algae
Cercozoans, radiolarians
Chapter 27
Stramenopiles (water molds, diatoms, golden algae, brown algae)
Alveolates (dinoflagellates, apicomplexans, ciliates)
Euglenozoans
Diplomonads, parabasalids
Euryarchaeotes, crenarchaeotes, nanoarchaeotes
Korarchaeotes
Gram-positive bacteria
Cyanobacteria
Spirochetes
Chlamydias
Proteobacteria
LE 26-22a
Chapter 28
• Eukaryotic cells have DNA in a nucleus that is
bounded by a membranous nuclear envelope
• Eukaryotic cells have membrane-bound
organelles
• Eukaryotic cells are generally much larger than
prokaryotic cells
• The logistics of carrying out cellular metabolism
sets limits on the size of cells
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-7
Surface area increases while
Total volume remains constant
5
1
1
Total surface area
(height x width x
number of sides x
number of boxes)
Total volume
(height x width x length
PowerPoint
Lecturesoffor
X number
boxes)
6
150
750
1
125
125
6
1.2
6
Biology, Seventh Edition
Neil Campbell
and Jane Reece
Surface-to-volume
ratio
(surface area  volume)
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-8
Outside of cell
Carbohydrate side chain
Hydrophilic
region
Inside of cell 0.1 µm
Hydrophobic
region
Hydrophilic
PowerPoint Lectures for region
Biology,
Seventh
TEM of
a plasmaEdition
membrane
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Phospholipid
Proteins
Structure of the plasma membrane
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 © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-9a
ENDOPLASMIC RETICULUM (ER
Nuclear envelope
Rough ER
Flagellum
Smooth ER
NUCLEUS
Nucleolus
Chromatin
Centrosome
Plasma membrane
CYTOSKELETON
Microfilaments
Intermediate filaments
Microtubules
Ribosomes:
Microvilli
PowerPoint Lectures for
Biology, Seventh
Edition
Peroxisome
Golgi apparatus
Neil Campbell and Jane Reece
Mitochondrion
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Lysosome
In animal cells but not plant cells:
Lysosomes
Centrioles
Flagella (in some plant sperm)
LE 6-9b
Nuclear
envelope
NUCLEUS
Nucleolus
Rough
endoplasmic
reticulum
Chromatin
Smooth
endoplasmic
reticulum
Centrosome
Ribosomes
(small brown dots)
Central vacuole
Golgi
apparatus
Microfilaments
Intermediate
filaments
Microtubules
CYTOSKELETON
Mitochondrion
Peroxisome
Chloroplast
Plasma
membrane
PowerPoint Lectures for
Cell wall
Biology, Seventh Edition
Neil Campbell
and Jane Reece
Wall of adjacent cell
Plasmodesmata
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
In plant cells but not animal cells:
Chloroplasts
Central vacuole and tonoplast
Cell wall
Plasmodesmata
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 © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
The Nucleus: Genetic Library of the Cell
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-10
Nucleus
Nucleus
1 µm
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Rough ER
Surface of nuclear envelope
PowerPoint Lectures for
0.25 µm
Biology, Seventh Edition
Neil Campbell and Jane Reece
Ribosome
1 µm
Close-up of nuclear
envelope
Lectures
by Chris(TEM)
Romero
Pore complexes
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Nuclear lamina (TEM)
Ribosomes: Protein Factories in the Cell
• 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
(ER) or the nuclear envelope (bound
ribosomes)
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-11
Ribosomes
ER
Cytosol
Endoplasmic
reticulum (ER)
Free ribosomes
Bound ribosomes
Large
subunit
Small
subunit
0.5 µm
PowerPoint Lectures for
Biology, Seventh EditionTEM showing ER
Neil Campbell and Jane Reece
and ribosomes
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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 © 2005 Pearson Education, Inc. publishing as 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-12
Smooth ER
Rough ER
Nuclear
envelope
ER lumen
Cisternae
Ribosomes
Transport vesicle
Smooth ER
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Transitional ER
Rough ER
200 nm
Functions of Smooth ER
• The smooth ER
– Synthesizes lipids
– Metabolizes carbohydrates
– Stores calcium
– Detoxifies poison
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Functions of Rough ER
• The rough ER
– Has bound ribosomes
– Produces proteins and membranes, which are
distributed by transport vesicles
– Is a membrane factory for the cell
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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 © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-13
Golgi
apparatus
cis face
(“receiving” side of
Golgi apparatus)
Vesicles also
transport certain
proteins back to ER
Vesicles move
from ER to Golgi
Vesicles coalesce to
form new cis Golgi cisternae
0.1 µm
Cisternae
Cisternal
maturation:
Golgi cisternae
move in a cisto-trans
direction
PowerPoint Lectures for
Biology, Seventh Edition
Neil
Campbell and Jane Reece
Vesicles transport specific
proteins backward to newer
Golgi cisternae
Vesicles form and
leave Golgi, carrying
specific proteins to
other locations or to
the plasma membrane for secretion
trans face
(“shipping” side of
Golgi apparatus)
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
TEM of Golgi apparatus
Lysosomes: Digestive Compartments
• A lysosome is a membranous sac of hydrolytic
enzymes
• Lysosomal enzymes can hydrolyze proteins, fats,
polysaccharides, and nucleic acids
• Lysosomes also use enzymes to recycle
organelles and macromolecules, a process called
autophagy
Animation: Lysosome Formation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-14a
1 µm
Nucleus
Lysosome
Lysosome contains Food vacuole Hydrolytic
active hydrolytic
enzymes digest
fuses with
enzymes
food particles
lysosome
Digestive
enzymes
Plasma
membrane
PowerPoint Lectures for Lysosome
Biology, Seventh Edition
Neil Campbell and Jane Reece
Digestion
Food vacuole
Lectures by Chris Romero
Phagocytosis: lysosome digesting food
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-14b
Lysosome containing
two damaged organelles
1 µm
Mitochondrion
fragment
Peroxisome
fragment
Lysosome fuses with
vesicle containing
damaged organelle
Hydrolytic enzymes
digest organelle
components
Lysosome
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris
Digestion
Vesicle containing
damaged mitochondrion
Autophagy: lysosome breaking down
Romero
damaged organelle
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Vacuoles: Diverse Maintenance Compartments
• Vesicles and vacuoles (larger versions of
vacuoles) are membrane-bound sacs with varied
functions
• A plant cell or fungal cell may have one or several
vacuoles
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
• 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
Video: Paramecium Vacuole
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-15
Central vacuole
Cytosol
Tonoplast
Nucleus
Central
vacuole
PowerPoint Lectures for
Biology, Seventh Edition Cell wall
Neil Campbell and Jane Reece
Chloroplast
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
5 µm
The Endomembrane System: A Review
• The endomembrane system is a complex and
dynamic player in the cell’s compartmental
organization
Animation: Endomembrane System
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-16-1
Nucleus
Rough ER
Smooth ER
Nuclear envelope
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-16-2
Nucleus
Rough ER
Smooth ER
Nuclear envelope
cis Golgi
Transport vesicle
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
trans Golgi
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-16-3
Nucleus
Rough ER
Smooth ER
Nuclear envelope
cis Golgi
Transport vesicle
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Plasma
membrane
trans Golgi
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Concept 6.5: Mitochondria and chloroplasts
change energy from one form to another
• Mitochondria are the sites of cellular respiration
• Chloroplasts, found only in plants and algae, are
the sites of photosynthesis
• Mitochondria and chloroplasts are not part of the
endomembrane system
• Peroxisomes are oxidative organelles
Copyright © 2005 Pearson Education, Inc. publishing as 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-17
Mitochondrion
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
PowerPoint Lectures for
Biology, Seventh Edition
Inner
membrane
Cristae
Neil Campbell and Jane Reece
Mitochondrial
DNA
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Matrix
100 nm
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
• Chloroplast structure includes:
– Thylakoids, membranous sacs
– Stroma, the internal fluid
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-18
Chloroplast
Ribosomes
Stroma
Chloroplast
DNA
Inner and outer
membranes
PowerPoint Lectures for
Biology, Seventh Edition
Granum
Neil Campbell and Jane Reece
Thylakoid
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1 µm
Peroxisomes: Oxidation
• Peroxisomes are specialized metabolic
compartments bounded by a single membrane
• Peroxisomes produce hydrogen peroxide and
convert it to water
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-19
Chloroplast
Peroxisome
Mitochondrion
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
1 µm
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-20
Microtubule
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Microfilaments
0.25 µm
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 © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-21a
Vesicle
ATP
Receptor for
motor protein
protein
PowerPoint LecturesMotor
for
Biology, Seventh Edition
(ATP powered)
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Microtubule
of cytoskeleton
LE 6-21b
Microtubule
Vesicles
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
0.25 µm
Components of 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cell Walls of Plants
• The cell wall is an extracellular structure that
distinguishes plant cells from animal cells
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Cell Walls of Plants
• 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
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-28
Central
vacuole
of cell
Plasma
membrane
Secondary
cell wall
Primary
cell wall
Central
vacuole
of cell
Middle
lamella
1 µm
Central vacuole
Cytosol
Plasma membrane
PowerPoint Lectures for
Biology, Seventh Edition
Plant cell walls
Neil Campbell and Jane Reece
Lectures by Chris Romero
Plasmodesmata
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
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 and other
macromolecules
• Functions of the ECM:
– Support
– Adhesion
– Movement
– Regulation
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-29a
Collagen
fiber
EXTRACELLULAR FLUID
Fibronectin
Plasma
membrane
PowerPoint Lectures for
Biology, Seventh Edition
Integrin
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
CYTOPLASM
Microfilaments
Proteoglycan
complex
LE 6-29b
Proteoglycan
complex
Polysaccharide
molecule
Carbohydrates
Core
protein
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Proteoglycan
molecule
Intercellular Junctions
• Neighboring cells in tissues, organs, or organ
systems often adhere, interact, and communicate
through direct physical contact
• Intercellular junctions facilitate this contact
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Plants: Plasmodesmata
• 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 © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-30
Cell walls
Interior
of cell
Interior
of cell
PowerPoint Lectures
0.5 µm for
Biology, Seventh Edition
Plasmodesmata
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Plasma membranes
Animals: Tight Junctions, Desmosomes, and Gap Junctions
• 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
Animation: Tight Junctions
Animation: Desmosomes
Animation: Gap Junctions
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
LE 6-31
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
0.5 µm
Tight junction
Intermediate
filaments
Desmosome
1 µm
Space
between
cells for
Lectures
Gap
junctions
PowerPoint
Biology, Seventh Edition
Plasma membranes
NeilofCampbell
and Jane Reece
adjacent cells
Gap junction
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings
Extracellular
matrix
0.1 µm
5 µm
LE 6-32
PowerPoint Lectures for
Biology, Seventh Edition
Neil Campbell and Jane Reece
Lectures by Chris Romero
Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings