campbell outline biology - napa valley college … 120 fall 2014 new...campbell biology reece...
Post on 26-Mar-2018
217 Views
Preview:
TRANSCRIPT
1
CAMPBELL
BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson
© 2014 Pearson Education, Inc.
TENTH
EDITION
6A Tour of
the Cell
Lecture Presentation by
Dr Burns
NVC
Outline
I. Cell Theory
II. Studying cells
III. Prokaryotic vs Eukaryotic
IV. Eukaryotic
A. Animal cells
B. Plant cells
Cells
Cells are the basic unit of life
Cells maintain homeostasis
They are enclosed in a phospholipid
membrane - the Plasma Membrane
Cells vary in size but there is a limit on how
big a cell can be and survive
There are different types of cells –
specialized cells4
Cell Theory
Cells were discovered in 1665 by Robert
Hooke.
Early studies of cells were conducted by
- Mathias Schleiden (1838)
- Theodor Schwann (1839)
Schleiden and Schwann proposed the Cell
Theory.
Cell Theory
1. All organisms are composed of cells.
2. Cells are the smallest living things.
3. Cells arise only from pre-existing cells.
All cells today represent a continuous line of
descent from the first living cells.
5 6
Cell Size
Cell size is limited.
-As cell size increases, it takes longer for
material to diffuse from the cell membrane to
the interior of the cell.
Small cells have a greater surface area
relative to volume
Surface area-to-volume ratio: as a cell
increases in size, the volume increases 10x
faster than the surface area
2
Surface area increases while
total volume remains constant
Total surface area[sum of the surface areas(height width) of all boxsides number of boxes]
Total volume[height width length number of boxes]
Surface-to-volume(S-to-V) ratio[surface area volume]
1
5
6 150 750
1
1251251
1.26 6
Figure 6.7
Some organisms are just one cell - yeast
Multi-celled organisms have specialized cells
Blood Cells Nerve Cells
Figure 6.1
Some cells are very small 10 m
1 m
0.1 m
1 cm
1 mm
100 mHuman egg
Frog egg
Chicken egg
Length of some
nerve and
muscle cells
Human height
Un
aid
ed
eye
Figure 6.2a
3
Figure 6.2b
1 mm
100 m
10 m
1 m
100 nm
10 nm
1 nm
0.1 nm Atoms
Small molecules
Lipids
Proteins
Ribosomes
Viruses
Smallest bacteria
Mitochondrion
Most bacteria
Nucleus
Most plant and
animal cells
Human egg
Lig
ht
mic
rosc
op
y
Ele
ctr
on
mic
rosc
op
y
Super-
resolution
microscopy
1 cm
Frog egg
Copyright © 2009 Pearson Education, Inc.
As the size of a cell increase, the surface
area:volume ratio
1 2 3
33% 33%33%1. Increase
2. Decrease
3. Stays the same
Cell fractionation
Used to study organelles
Homogenize the sample
Lyse the cells (break open) and the resulting
cell extract spun in a centrifuge
Cell fractionation
Centrifugal force separates extract
Pellet – bottom of tube, contains large
components of cell, organelles like nucleus
Supernatant – liquid on top of pellet, contains
lighter components
Homogenate
Homogenization
Tissue cells
Centrifugation
1,000 g10 min
20,000 g20 min
80,000 g60 min
150,000 g3 hr
Pellet rich inribosomes
Pellet rich in“microsomes”
Pellet rich inmitochondriaand chloroplasts
Pellet rich innuclei andcellular debris
Differentialcentrifugation
Supernatant poured into next tube
4
Cell Fractionation
1000 g x 10 min = nuclei in pellet
20,000 g x 20 min = mitochondria, chloroplast
80,000 g x 60 min = microsomal fraction contains:
ER, Golgi, plasma membrane
150,000 g x 3 hr = ribosomes
To separate the ER, Golgi and plasma
membrane you can use a density gradient
centrifuge
If you centrifuge cells at 80,000 g which fraction will contain
the endoplasmic reticulum?
1. Pellet
2. Supernate
Pel
let
Super
nate
50%50%
Inner Life of a Cell - Harvard
Inner life of a cell - short version, music
only
22
Cell Structures
All cells have certain structures in common.
1. genetic material – in a nucleoid region or
nucleus
2. cytoplasm – a semifluid matrix (fluid portion is
the cytosol)
3. plasma membrane – a phospholipid bilayer
4. Ribosomes (make proteins)
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
© 2011 Pearson Education, Inc.
Plasma MembraneOutside of cell
Inside of cell0.1 m
(a) TEM of a plasmamembrane
Hydrophilicregion
Hydrophobicregion
Hydrophilicregion
Carbohydrate side chains
ProteinsPhospholipid
(b) Structure of the plasma membrane
5
Copyright © 2009 Pearson Education, Inc.
The main component of the plasma
membrane is:
1 2 3 4
25% 25%25%25%1. Trigylcerides
2. Cholesterol
3. Protein
4. Phospholipids
Prokaryotic vs Eukaryotic
Prokaryotic – Pro (before) karyotic (nucleus)
Eukaryotic – Eu (true) karyotic (nucleus)
The presence or absence of a nucleus is the
most obvious difference between these types of
cells.
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
© 2011 Pearson Education, Inc.
Fimbriae
Bacterial
chromosome
A typicalrod-shapedbacterium
(a)
Nucleoid
Ribosomes
Plasma
membrane
Cell wall
Capsule
Flagella A thin sectionthrough thebacterium Bacilluscoagulans (TEM)
(b)
0.5 m
Figure 6.5
A thin section through thebacterium Bacillus coagulans(TEM)
(b)
0.5 m
Prokaryotic Cells – Characteristics and Features
1. Include bacteria and archaea
2. Has no nucleus, have nucleoid region
3. Also lack membrane bound compartments
(organelles)
4. Many use folds in the plasma membrane to
accomplish the tasks of organelles
5. Many prokaryotic cells have cell walls
6. Some have a capsule
6
Prokaryotic Cells – Characteristics and Features
6. Have a plasma membrane
7. Have cytoplasm
8. Many have flagella for locomotion
9. Contain ribosomes for protein production
10. Have storage granules – contain glycogen,
lipids, and phosphate compounds
11. Some can perform photosynthesis
Prokaryotic cells have a nucleus
1. True
2. False
Tru
e
Fal
se
50%50%
Copyright © 2009 Pearson Education, Inc.
Do prokaryotic cells contain ribosomes?
1 2 3
33% 33%33%1. Yes
2. No
3. Some do
Eukaryotic cells
Highly organized, have organelles including
a nucleus. Eukaryotic cells are generally
much larger than prokaryotic cells
Animal cells
Plant cells
Protists
Fungi
Major Features of Animal Cells
Structures:
1. Plasma membrane – controls entry in/out of cell
2. Cytoplasm – semi-fluid matrix outside the
nucleus, liquid portion is the cytosol
3. Ribosomes - assembling polypeptide chains
4. Chromosomes – DNA + proteins
5. Cytoskeleton - gives shape, structure, transport
6. Flagella - movement
Major Features of Animal Cells
Membrane bound Organelles
1. Nucleus – contains the DNA
2. Mitochondria – energy production
3. Endoplasmic reticulum – modifies new polypeptide
chains (rough) and synthesizes lipids (smooth)
4. Golgi body – modifies, sorts, ships new proteins
and lipids
5. Vesicles – storage, transport, digestion
6. Lysosomes – digestion
7. Peroxisomes – lipid metabolism
7
Flagellum
Centrosome
CYTOSKELETON:
Microfilaments
Intermediate filamentsMicrotubules
Microvilli
Peroxisome
MitochondrionLysosome
Golgi apparatus
Ribosomes
Plasmamembrane
Nuclearenvelope
Nucleolus
Chromatin
NUCLEUS
ENDOPLASMICRETICULUM (ER)
Rough ER Smooth ER
What kind of tissue is this?
Human cells from liningof uterus (colorized TEM)
Cell
Nucleus
Nucleolus
10 μ
m
© 2011 Pearson Education, Inc.
BioFlix: Tour of an Animal Cell
Cell Membranes
1. Plasma membrane: Divides outside from
inside of cell
2. Organelles: specialized membrane bound
compartments
Organelles
Compartments allow the cells to keep reactive
compounds from causing injury
Some membranes form vesicles that are used
for transporting things
Some membranes are attached to other
membranes
Organelle/feature Function
Nucleus Contains DNA
DNA is copied to make RNA
Ribosomes “reads” mRNA to assemble amino acids
into a polypeptide chain
Rough Endo Ret Polypeptide chain that are to be exported
or membrane bound are processed here
Golgi complex Further processes and sorts proteins to be
exported or membrane bound
Vesicles Transports proteins
Protein Production/Synthesis
8
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
© 2011 Pearson Education, Inc.
Nucleus
Nucleus protects DNA
Separates DNA from rest of cell
Place where DNA replicates itself
Place where DNA is copied to make RNA
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
© 2011 Pearson Education, Inc.
1 μm Nucleus
NucleolusChromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Nucleus
RoughER
Chromatin
Nuclear lamina (TEM)
Close-upof nuclearenvelope
Pore complexes (TEM)
0.2
5 μ
m
0.5
μm
Porecomplex
Ribosome
Surface ofnuclear envelope(TEM)
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Nucleus
RoughER
Chromatin
Porecomplex
Ribosome
Close-upof nuclearenvelope
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
and lines the inside of the nuclear envelope
© 2011 Pearson Education, Inc.
9
In the nucleus, DNA is organized into discrete
units called chromosomes
Each chromosome is composed of a single DNA
molecule associated with proteins
The proteins are called histones
The DNA and the histones are together called
chromatin
Chromatin condenses to form discrete
chromosomes as a cell prepares to divide
© 2011 Pearson Education, Inc.
Parts of the Nucleus
2. Nucleolus – dense area in the nucleus is
where rRNA are produced and ribosomes
are assembled
3. Nucleoplasm – area within nucleus
Ribosomes: Protein Factories
Ribosomes are particles made of ribosomal RNA
and protein
Proteins are made at ribosomes
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)
© 2011 Pearson Education, Inc.
Ribosomes
Has two components: a small subunit and a
large subunit
Each subunit is made up of strands of rRNA
and many proteins
The ribosome is like the workbench for
assembling polypeptide chains. It is here that
amino acids are bound together with a peptide
bond.
Figure 6.10
0.25 m
Free ribosomes in cytosol
Endoplasmic reticulum (ER)
Ribosomes bound to ER
Large
subunit
Small
subunit
Diagram of a ribosomeTEM showing ER and
ribosomes
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.
10
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, surface is studded with ribosomes
© 2011 Pearson Education, Inc.
Endoplasmic reticulum
Network of folded internal membranes
located in the cytoplasm
Attached to nucleus
Lumen = space inside endoplasmic reticulum
Figure 6.11 Smooth ER
Rough ER
ER lumen
CisternaeRibosomes
Smooth ER
Transport vesicle
Transitional ER
Rough ER200 nm
Nuclear
envelopeFunctions of Smooth ER
Functions of the smooth ER
1. Synthesizes lipids
2. Metabolizes carbohydrates
3. Detoxifies drugs and poisons
4. Stores calcium ions
© 2011 Pearson Education, Inc.
Functions of Rough ER
The functions of the rough ER
1. Important in protein production = folds and tags
the newly made proteins
2. Creates transport vesicles that go to the golgi
© 2011 Pearson Education, Inc.
Rough Endoplasmic Reticulum (RER)
RER has bound ribosomes
Ribosomes that are producing polypeptide
chains for export or to be embedded in
membranes dock with the surface of the
RER
The growing polypeptide chain enters the
lumen of the RER
11
Functions of Rough Endoplasmic Reticulum (RER)
In the RER the polypetide chain is folded
Enzymes called molecular chaperones aid in the
folding of the polypeptide chains into proteins
Some of the polypeptide chains may get modified
here “tagged” with carbohydrate chain =
glycoproteins
The polypeptide chains/proteins are put into
transport vesicles
The Golgi apparatus consists of flattened
membranous sacs called cisternae
Functions of the Golgi apparatus
1. Modifies products of the ER
2. Sorts and packages materials into transport
vesicles
3. Produces lysosomes
The Golgi Apparatus: Shipping and Receiving Center
© 2011 Pearson Education, Inc.
Figure 6.12
cis face
(“receiving” side of
Golgi apparatus)
trans face
(“shipping” side of
Golgi apparatus)
0.1 m
TEM of Golgi apparatus
Cisternae
V Cell Movie
Golgi – Protein Trafficking
Copyright © 2009 Pearson Education, Inc.
All polypeptide chains go to the RER
1 2
50%50%1. True
2. False
Protein Production - Overview
1. DNA in the nucleus are the instructions for making
protein
2. A copy of the DNA is made = mRNA
3. mRNA leaves the nucleus
4. mRNA docks with a ribosome to assemble a chain
of amino acids.
5. tRNA brings amino acids to ribosomes
6. At the ribosome the amino acids are linked together
with a peptide bond to form a polypeptide chain
12
Protein Production Cont
7. Ribosome with the growing polypeptide chain docks with the rough endoplasmic reticulum if the protein is to be exported or embedded in a membrane
8. The polypeptide chain enters the lumen of the RER where they are folded and may get a carbohydrate “tag” attached to it
9. The RER buds off a transport vesicles that can carry the newly formed proteins to the golgi
Protein Production Cont
10. The golgi processes, sorts, packages proteins and lipids from the RER and SER
11. Proteins that are exported are shipped in transport vesicles to the plasma membrane
12. Proteins may be put into lysosomes
13. Proteins that are membrane bound are embedded in the transport vesicles membrane
Cytosolic proteins
Proteins that are not shipped out of cell
are made on free floating ribosomes
Chaperone proteins fold the proteins in the
cytosol
Lysosomes
Produced by the Golgi
Lysosomes are small membrane bound sacs that
contain digestive enzymes. The pH is relatively
acidic (pH 5) in the lysosomes.
Because the lysosomes are acidic and contain
digestive enzymes, their contents must be kept
separate from the rest of the cell
Lysosomes
1. Contain strong acids and enzymes
2. Engulf molecules and digest them or
3. Fuse with other organelles and vesicles to destroy them
4. Can fuse with plasma membrane to expel waste
5. Destroy bacteria
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
© 2011 Pearson Education, Inc.
13
Video: Phagocytosis in ActionFig. 4.14
Figure 6.13
Nucleus
Lysosome
1 m
Digestive
enzymes
Digestion
Food vacuole
LysosomePlasma membrane
(a) Phagocytosis
Vesicle containing
two damaged
organelles1 m
Mitochondrion
fragment
Peroxisome
fragment
(b) Autophagy
Peroxisome
VesicleMitochondrion
Lysosome
Digestion
Scavenger cells
Throughout the
body there are
scavenger cells
that engulf
bacteria, foreign
material or old
cellular material
Tay-Sachs Disease
Tay-Sachs is a hereditary disease –
people with this disease don’t have an enzyme normally found in lysosomes that breaks down lipids in nerve cells.
Vacuoles: Diverse Maintenance Compartments
Plant cell, protists, and fungal cells may have one or several vacuoles, derived from endoplasmic reticulum and Golgi apparatus
© 2011 Pearson Education, Inc.
14
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
© 2011 Pearson Education, Inc.
Vacuoles: Diverse Maintenance Compartments Mitochondria produce ATP
• Mitochondria are the sites of cellular respiration,
a metabolic process that uses oxygen to generate
ATP
© 2011 Pearson Education, Inc.
Mitochondria
Most all Eukaryotic cells (plants, animals, fungi
and protists) contain mitochondria
Produces energy for the cell (ATP)
Cells that require lots of energy have lots of
mitochondria (liver cells can have over 1000
mitochondria
Requires oxygen = site of aerobic respiration
Important in apoptosis (programmed cell death)
Mitochondria - Structure
Bound by a double membrane
Forms two compartments
Outer membrane faces cytoplasm
Inner membrane folded forming cristae which
increases surface area
The cristae contain many enzymes and other proteins
important for cellular respiration
Intermembrane space is between outer and inner
membrane
Mitochondria contain its own DNA
Mitochondria
The double membrane structure is important in
its function (cellular respiration) and to keep
dangerous oxygen species and free radicals
from damaging the cells.
Figure 6.17
Intermembrane space
Outer
membrane
DNA
Inner
membrane
Cristae
Matrix
Free
ribosomes
in the
mitochondrial
matrix
(a) Diagram and TEM of mitochondrion (b) Network of mitochondria in a protist
cell (LM)
0.1 m
Mitochondrial
DNA
Nuclear DNA
Mitochondria
10 m
15
Apoptosis
Apoptosis is planned cell death
In contrast, necrosis is uncontrolled cell death
When a cell is no longer needed or is not
functioning properly, the cell will undergo
apoptosis.
Apoptosis
Mitochondria can initiate apoptosis in several
ways – one way is through a cascade of
enzymatic reactions.
When the mitochondria gets the signal to
begin apoptosis it releases cytochrome c,
which activates a group of enzymes called
caspases
Apoptosis Video
Apoptosis
Peroxisomes
Peroxisomes are membrane bound vesicles that contain oxidative enzymes
These enzymes function by oxidizing their substrates (many of their substrates are fatty acids)
16
Peroxisomes
Oxidation is when a substance loses an electron
RH2 + O2 → RH + H2O2
This produces H2O2 which is dangerous therefore another enzyme, catalase, removes the H2O2
2 H2O2 → O2 + 2H2O
Functions of Peroxisomes
Involved in lipid metabolism and detoxification
Contain enzymes that produce and degrade hydrogen peroxide
Fig. 4.15
What organelle produces energy (ATP)?
1 2 3 4 5
20% 20% 20%20%20%1. Ribosomes
2. Golgi complex
3. Mitochondria
4. SER
5. Lysosomes
Where are polypeptide chains assembled?
1 2 3 4
25% 25%25%25%1. Ribosomes
2. Golgi complex
3. SER
4. RER
Where are lipids synthesized?
1 2 3 4 5
20% 20% 20%20%20%1. Ribosomes
2. Golgi complex
3. Peroxisomes
4. SER
5. Lysosomes
17
These are membrane bound sacs with digestive enzymes
1 2 3 4 5
20% 20% 20%20%20%1. Ribosomes
2. Golgi complex
3. Mitochondria
4. SER
5. Lysosomes
Inner Life of a Cell - Harvard
Inner Life of a Cell Narrated, long version
Cytoskeleton
Interconnected system of fibers and lattices
Gives cells their organization, shape, ability to
move, transport things in cell, important in cell
division
Some permanent others only present when
needed
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
© 2011 Pearson Education, Inc.
Fig. 4.20
Tubulin dimer
25 nm
Column of tubulin dimers
10 m
Table 6.1a
18
Microtubules
Thickest type of cytoskeleton
Important in
The structure of cell – cell shape
Cell division – separates the chromosomes
Transport of organelles in the cell
Movement of cells (cilia and flagella)
Microtubules
Composed of two proteins that form a dimer:
α-tubulin and β-tubulin.
These assemble by adding dimers and
disassemble by removing them
Structural microtubule-associated proteins
(MAPs) regulate microtubule assembly
-Tubulin
-Tubulin
Dimer
Plus end
Minus endDimer on
Dimers off
(a)
Microtubule Anchoring
Microtubules may be anchored in the
microtubule-organizing centers (MTOCs)
In animal cells the main MTOC is the
centrosome – this is important in cell division
The centrosome is composed of two
centrioles
The centrioles have nine sets of three
microtubules
Centrosome
Longitudinalsection ofone centriole
Centrioles
Microtubule
0.25 m
Microtubules Cross section
of the other centriole
Figure 6.22Fig. 4.21
19
Microtubules – cell division
During cell division much of the cytoskeleton
breaks down and microtubule form that will
help in cell division = spindles
Spindles move the chromosomes so when the
cell divides the chromosomes are evenly
divided
Microtubule – transport of organelles
Microtubule can be used to transport vesicles
and other structures.
The microtubule is stationary, transport proteins
(kinesin and dynein) move the item.
Kinesin moves items in one direction
Dynein moves items in the opposite direction
Fig. 4.22
Cilia and flagella
Microtubules important in movement of the cell
Project from cell surface
Flagella are long microtubules
Cilia are short microtubules
Flagella are found on sperm and many one celled organisms
Cilia found on many one celled organisms and on cells that line passageways in multi-celled organisms
114
Cilia and Flagella
20
Flagella and Cilia
Both flagella and cilia have nine pairs of
microtubules in an outer ring and a pair in the
center (9 pairs + pair in center).
Anchored by a basal body (9 triplets)
A motor protein called dynein, which drives
the bending movements of a cilium or
flagellum
© 2011 Pearson Education, Inc.
Animation: Cilia and Flagella
Right-click slide / select “Play”
Microtubules
Plasmamembrane
Basal body
Longitudinal sectionof motile cilium
(a)
0.5 m 0.1 m
0.1 m
(b) Cross section ofmotile cilium
Outer microtubuledoublet
Dynein proteins
Centralmicrotubule
Radialspoke
Cross-linkingproteins betweenouter doublets
Plasma membrane
Triplet
(c) Cross section ofbasal body
Figure 6.24
Fig. 4.24b
21
Direction of swimming
(b) Motion of cilia
Direction of organism’s movement
Power stroke Recovery stroke
(a) Motion of flagella5 m
15 m
Figure 6.23
Cilia
Microfilaments
Microfilaments are made two chains of actin
protein molecules
Important in:
1. providing support for cell structures
2. movement of cells (ameoba-like movement)
3. dividing cells in two
4. stabilizing microvilli structure
Microfilaments (Actin Filaments)
Microfilaments are solid rods about 7 nm in
diameter, built as a twisted double chain of actin
subunits
The structural role of microfilaments is to bear tension, resisting pulling forces within the cell
They form a 3-D network just inside the plasma membrane to help support the cell’s shape
Bundles of microfilaments make up the core of microvilli of intestinal cells
© 2011 Pearson Education, Inc.
Microfilaments are in green Microfilaments
Actin molecules will assemble to form
microfilaments
Microfilaments are important in formation of
microvilli
22
Figure 6.26
Microvillus
Plasma membrane
Microfilaments (actin
filaments)
Intermediate filaments
0.25 m
Microfilaments that function in muscles 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 interact
with the thinner actin fibers
© 2011 Pearson Education, Inc.
Microfilaments Role in Movement - Muscle
Figure 6.27a Muscle Cells
Muscle cell
Actinfilament
Myosin
Myosin
filament
(a) Myosin motors in muscle cell contraction
0.5 m
head
Pseudopodia (cellular extensions) extend and
contract through the reversible assembly actin
subunits into microfilaments
Localized contraction brought about by actin and
myosin also drives amoeboid movement
© 2011 Pearson Education, Inc.
Microfilaments Role in Movement - Pseudopodia
Figure 6.27b
100 m
Cortex (outer cytoplasm):
gel with actin network
Inner cytoplasm: sol
with actin subunits
(b) Amoeboid movement
Extending
pseudopodium
23
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 drive
cytoplasmic streaming
© 2011 Pearson Education, Inc.
Microfilaments Role in Movement – Cytoplasmic streaming Figure 6.27c
30 m(c) Cytoplasmic streaming in plant cells
Chloroplast
Intermediate filaments
Do not self assemble/disassemble –
permanent
Important in cell shape
Tough but flexible fibers
Found in high amounts in cells that are
subjected to mechanical stress (in skin)
Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis (ALS) is
caused by abnormal intermediate filaments
in nerve cells
Fig. 4.20.c
Cilia and flagella are composed of this type of cytoskeleton
1. Microtubules
2. Microfilaments
3. Intermediate
filaments
Mic
rotu
bules
Mic
rofil
amen
ts
Inte
rmed
iate
fila
men
ts
33% 33%33%
24
Microfilaments are composed of:
1 2 3 4
25% 25%25%25%1. Kinesin
2. Actin
3. Tubulin
4. Dynein
Copyright © 2009 Pearson Education, Inc.
This type of cytoskeleton is more permanent
1 2 3
33% 33%33%1. Microtubules
2. Microfilaments
3. Intermediate
Fibers
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.
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
ECM proteins bind to receptor proteins in the
plasma membrane called integrins
© 2011 Pearson Education, Inc.
Figure 6.30a
EXTRACELLULAR FLUIDCollagen
Fibronectin
Plasmamembrane
Micro-filaments
CYTOPLASM
Integrins
Proteoglycancomplex
Functions of the ECM
Support
Adhesion
Movement
Regulation
© 2011 Pearson Education, Inc.
Functions of the Extracellular Matrix (ECM) of
Animal Cells
25
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 (in Plants)
Tight junctions
Desmosomes
Gap junctions
© 2011 Pearson Education, Inc.
Plasmodesmata in Plant Cells
Plasmodesmata are channels that perforate
plant cell walls
Plasmodesmata allow water and small solutes
(and sometimes proteins and RNA) to pass from
cell to cell
© 2011 Pearson Education, Inc.
Figure 6.31
Interior
of cell
Interior
of cell
0.5 m Plasmodesmata Plasma membranes
Cell walls
Cell 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.
Figure 6.32
Tight junctions prevent
fluid from moving
across a layer of cells
Tight junction
Tight junction
TEM0.5 m
TEM1 m
TE
M
0.1 m
Extracellular
matrixPlasma membranes
of adjacent cells
Space
between cells
Ions or small
molecules
Desmosome
Intermediate
filaments
Gap
junction
© 2011 Pearson Education, Inc.
Animation: Tight Junctions
Right-click slide / select “Play”
26
Tight junctions
Tight junctions: prevent substances from
leaking across tissues
Found in high concentration between
cells:
Lining the digestive system
Lining capillaries in the brain
© 2011 Pearson Education, Inc.
Animation: Desmosomes Right-
click slide / select “Play”
Desmosomes Anchoring junctions
Desmosomes - Anchoring junctions:
hold adjacent cells together (like
glue) and allow tissues to be flexible
Found in high concentration in skin
epithelial cells
Integrin and Cadherin proteins
Attach to cytoskeleton
© 2011 Pearson Education, Inc.
Animation: Gap JunctionsRight-click slide / select “Play”
Communicating Junctions
Gap junctions – open channels between
cells allowing rapid communication due to
quick transfer of ions and small molecules
between neighboring cells
These junctions can be opened or closed
High concentration of gap junctions are
found in heart tissue
Animal and Plant cells
Both animal and plant cells have:
Plasma membrane
Nucleus
Smooth and rough endoplasmic reticulum
Ribosomes
Golgi complex
Vesicles
Peroxisomes
Mitochodria
Cytoskeleton
Lysosomes
27
Plant Cells
Plant cell components not present in animal
cells
Cell wall
Vacuoles (usually central)
Plastids including Chloroplast
Glyoxysomes
Not present in plant cells: centrioles
Found only in Animal Cells
Animal cells have centrioles, plants have a
different type of MTOCs
© 2011 Pearson Education, Inc.
BioFlix: Tour of a Plant Cell
NUCLEUS
Nuclearenvelope
Nucleolus
ChromatinRough ER
Smooth ER
Ribosomes
Central vacuole
Microfilaments
MicrotubulesCYTOSKELETON
Chloroplast
Plasmodesmata
Wall of adjacent cell
Cell wall
Plasmamembrane
Peroxisome
Mitochondrion
Golgiapparatus
Cells from duckweed(colorized TEM)
Cell wall
Cell
Chloroplast
Mitochondrion
Nucleus
Nucleolus
5 μ
m
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.
28
Cell Wall
Composed of :
1. Cellulose
2. Lignins
3. Sticky polysaccharides
4. Glycoproteins
Glyoxysomes
Plants also have a type of organelle called glyoxysomes
Glyoxysomes contain enzymes that convert stored fatty acids to sugar that is used for energy, this is especially important in germinating seedlings.
Animal cells do not have these type of peroxisomes (we can’t convert fatty acids to sugar)
Plastids
Chromoplasts – contain pigments, give plant
color, attract pollinators
Amyloplasts – store starch
Chlorplasts – contain a green pigment,
chlorophyll and carotenoids – yellow and
orange pigments. Site of photosynthesis.
Figure 6.14
Central vacuole
Cytosol
Nucleus
Cell wall
Chloroplast
Central
vacuole
5 m
Central Vacuole in Plants
Plant central vacuoles
Large area of cell space – up to 90%
Fluid filled with water, amino acids, sugars,
H+ ions, and wastes.
Stores nutrients
Digests wastes – similar to lysosomes in
animal cells
Chloroplasts
Chloroplasts, found in plants and algae, are the
sites of photosynthesis
© 2011 Pearson Education, Inc.
29
Chloroplasts: Capture of Light Energy
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
© 2011 Pearson Education, Inc.
Chloroplast structure includes
Thylakoids, membranous sacs, stacked to form a granum
Stroma, the internal fluid
The chloroplast is one of a group of plant organelles,
called plastids
© 2011 Pearson Education, Inc.
Chloroplasts: Capture of Light Energy
171
ChloroplastsFigure 6.18
RibosomesStroma
Inner and outer
membranes
Granum
1 mIntermembrane spaceThylakoid
(a) Diagram and TEM of chloroplast (b) Chloroplasts in an algal cell
Chloroplasts
(red)
50 m
DNA
Mitochondria and chloroplasts have similarities with
bacteria
Enveloped by a double membrane
Contain free ribosomes and circular DNA
molecules
Grow and reproduce somewhat independently in
cells
© 2011 Pearson Education, Inc.
The Evolutionary Origins of Mitochondria and
Chloroplasts
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.
The Evolutionary Origins of Mitochondria and
Chloroplasts
30
NucleusEndoplasmic
reticulum
Nuclear
envelope
Ancestor of
eukaryotic cells
(host cell)
Engulfing of oxygen-
using nonphotosynthetic
prokaryote, which
becomes a mitochondrion
Mitochondrion
Nonphotosynthetic
eukaryote
Mitochondrion
At least
one cell
Photosynthetic eukaryote
Engulfing of
photosynthetic
prokaryote
Chloroplast
Figure 6.16
Plant cells do not contain:
1 2 3 4
25% 25%25%25%1. Mitochondria
2. Centrioles
3. Nucleus
4. Ribosomes
Important Concepts
Know the vocabulary in the lecture
Be able to describe cell theory and the properties
of cells and structures common to all cells.
How are cells studied using centrifugation
techniques? How would you separate the
organelles of the cell?
What are the main difference between
prokaryotic cells and eukaryotic cells, and
examples of each type?
Important Concepts
What are the features and characteristics of
prokaryotic cells?
What is apoptosis and what organelle is an
important player in the process? What molecules
are released and activated during apoptosis?
What are the major features of eukaryotic cells,
their features, structure, and their functions – in
both plants and animals?
Important Concepts
Describe the steps needed to make a protein and
ship it out of the cells, or embed the protein in a
membrane, or have the protein stay in the
cytosol.
What is the cause of Tay Sachs disease?
What are the differences between plant and
animal cells?
Be able to describe the endosymbiont theory
Important Concepts
What are the types of cytoskeleton – what are
their functions, structure, what proteins are they
composed of, and how they are assembled?
How are microtubules assembled, anchored,
how do they transport items and what proteins
are used by microtubles to transport items.
What is the cause of ALS?
What are cell walls composed of, what are the
layers?
31
Know the types of cell junctions, their
functions and locations where there are
found in high concentration
Know the role and components of
extracellular matrix
Important Concepts
top related