Lecture 20: The Cytoskeleton: Intermediate Filaments and

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1. Lecture 20: The Cytoskeleton: Intermediate Filaments and
2. The Cytoskeleton Includes Dynamic NetworksOf Microfilaments And Microfilaments
3. The cytoskeleton consists of three major types
4. YPET – MAP R – MT PLUS
5. IntermediateFilamentsare non-dynamic and structural.They positionthe nucleusand insert into Desmosomesto hold neighboringcellstogether.
6. IntermediateFilamentspolymerizeto form strongrope-like fibers. The basic structural unit is a coiled-coildimer. Thesefibers are symmetric
7. The inner side of the nuclear envelopeis
8. Intermediate filament networks flare out from the
9. Microtubules Make Up Dynamic Networks
10. Microtubules serve four functions:To give shape to
11. Microtubules Are Made Of Tubulin Protofilaments
12. Microtubules as seen by ElectronMicroscopy1) thin section2) freeze driedAnd platinumShadowed
13. Microtubules are stabilized by capping at theirPlus
14. The centrosome consists of centrioles surrounded by
15. Microtubule assemblyat plus end is governed by
16. Catastrophic Disassembly can occur if growth at
17. DYNAMIC INSTABILITY IN A MICROTUBULE ASTER
18. MICROTUBULE DYNAMICS SEEN WITH FLUORESCENT PLUS END PROTEINS
19. MICROTUBULE DYNAMICS SEEN WITH FLUORESCENT PLUS END PROTEINS
20. Microtubule associated proteins also stabilize microtubules. Acetylation and tyrosylation do too.
21. Drugs can stabilize or destabilize microtubules; Taxol stabilizes existing mts; cholchicine destabilizes microtubules by monomer binding
22. Motor proteins “walk” on microtubules and microfilaments
23. Kinesin, like myosin, hydrolyzes ATP as it
24. MOTOR PROTEINS MOVE VESICLES ON MICROTUBULE TRACKS – A CONFORMATIONAL CYCLE THAT HYDROLYZES ATP
25. MOTOR PROTEINS MOVE VESICLES ON MICROTUBULE TRACKS
26. Direction of vesicleTransport on microtubules FIBROBLASTNEURONMovement of pigment granules on MTs
27. Cilia And Flagella: A Different Form Of Motility
28. Слайд 28
29. Dynein provides Motive forceto move oneMT doubletrelative to a neighboringMT doublet
30. DyneinMotors causemicrotubulesliding invitro; thesemotors causebending inan intactflagellum
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The Cytoskeleton Includes Dynamic NetworksOf Microfilaments And Microfilaments

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Lecture 20: The Cytoskeleton: Intermediate Filaments and

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Слайд 1Lecture 20:
The Cytoskeleton:
Intermediate Filaments and Microtubules

Essential
Cell Biology
Fourth Edition
Chapter 17

Слайд 2The Cytoskeleton Includes Dynamic Networks
Of Microfilaments And Microfilaments

Слайд 3The cytoskeleton consists of three major types
of filaments plus

many filament-associated
proteins including molecular motors
Microfilaments – composed of

actin, these
filaments form dynamic networks that form
the basis for cell shape and movement

Microtubules – composed of tubulin, these
tubules act as tracks on which to move
vesicles and organelles. They also form the
basis of cilia and flagella. They are dynamic.

Intermediate filaments – composed of proteins
that associate to form rope-like structures
that are of high mechanical strength. They
position organelles and form a strong, long
lasting cell superstructure.

The cytoskeleton consists of three major types of filaments plus many filament-associated proteins including molecular motors Microfilaments

Слайд 4YPET – MAP R – MT PLUS END
KERITAN – INTERMEDIATE

FIL.
ACTIN – STRESS FIBERS
ACTININ – STRESS FIBERS
VIMENTIN – INTERMEDIATE
TUBULIN -

MICROTUBULES

Cytoskeletal
Networks
Containing
Fluorescent
Proteins

Fluorescence
Microscopy allows
Visualization
Of cytoskeletal
Networks

YPET – MAP R – MT PLUS ENDKERITAN – INTERMEDIATE FIL.ACTIN – STRESS FIBERSACTININ – STRESS FIBERSVIMENTIN

Слайд 5Intermediate
Filaments
are non-
dynamic and
structural.
They position
the nucleus
and insert into
Desmosomes
to hold

neighboring
cells
together.

IntermediateFilamentsare non-dynamic and structural.They positionthe nucleusand insert into Desmosomesto hold neighboringcellstogether.

Слайд 6Intermediate
Filaments
polymerize
to form strong
rope-like fibers. The basic
structural unit is a

coiled-coil
dimer. These
fibers are symmetric

Слайд 7The inner side of the nuclear envelope
is lined by a

network of intermediate
filaments called lamins. They serve as
an anchoring site

for chromosomes as
well as for intermediate filament networks
that extend from the nucleus out into the
cytoplasm.

The inner side of the nuclear envelopeis lined by a network of intermediatefilaments called lamins. They serve

Слайд 8Intermediate filament networks flare out from the nucleus and insert

into plasma membrane junctions called desmosomes. Desmosomes connect the intermediate

filaments networks of neighboring cells forming a strong mechanical bond that keeps the cells from being pulled apart.

Intermediate filament networks flare out from the nucleus and insert into plasma membrane junctions called desmosomes. Desmosomes

Слайд 9Microtubules
Make Up
Dynamic
Networks

Слайд 10Microtubules serve four functions:

To give shape to the cell.
Example: nerve

axons contain numerous micro-
tubules along their length. If disrupted the

axon
shrivels.

2. To provide “tracks” on which to move
vesicles carrying cargo.
Example: pigment granules move outward
and inward from cell center using microtubules.

3. To form the mitotic spindle which separates
chromosomes during mitosis and meiosis.

To form flagella and cilia – whip like
structures that propel cells.

Microtubules serve four functions:To give shape to the cell.Example: nerve axons contain numerous micro-tubules along their length.

Слайд 11Microtubules Are Made Of Tubulin Protofilaments

Слайд 12Microtubules as seen by Electron
Microscopy

1) thin section

2) freeze dried
And platinum
Shadowed

Слайд 13Microtubules are stabilized by capping at their
Plus and minus ends.

Centrosomes and
Microtubule organizing centers (MTOCs) cap the
minus end;

special membrane-associated proteins
cap the plus end.

Microtubules are stabilized by capping at theirPlus and minus ends. Centrosomes and Microtubule organizing centers (MTOCs) cap

Слайд 14The centrosome consists of centrioles surrounded by a “protein cloud”.

Minus ends of microtubules are capped by gamma tubulin rings

and the centrosome serves as a microtubule organizing center (MTOC).

The centrosome consists of centrioles surrounded by a “protein cloud”. Minus ends of microtubules are capped by

Слайд 15Microtubule assembly
at plus end is governed
by GTP hydrolysis; GTP-
tubulin

is required for
polymerization;

But after hydrolysis,
GDP-tubulin
favors depolymerization

Microtubule assemblyat plus end is governed by GTP hydrolysis; GTP-tubulin is required forpolymerization; But after hydrolysis,GDP-tubulinfavors depolymerization

Слайд 16Catastrophic
Disassembly can occur if growth at the plus end

stops or is slow; but
the microtubule starts to grow

at this end again.

Catastrophic Disassembly can occur if growth at the plus end stops or is slow; but the microtubule

Слайд 17DYNAMIC INSTABILITY IN A MICROTUBULE ASTER

Слайд 18MICROTUBULE DYNAMICS SEEN WITH FLUORESCENT PLUS END PROTEINS

Слайд 19MICROTUBULE DYNAMICS SEEN WITH FLUORESCENT PLUS END PROTEINS

Слайд 20Microtubule associated proteins also stabilize microtubules.
Acetylation and
tyrosylation do

too.

Microtubule associated proteins also stabilize microtubules. Acetylation and tyrosylation do too.

Слайд 21Drugs can stabilize or destabilize microtubules;
Taxol stabilizes existing mts;

cholchicine
destabilizes microtubules by monomer binding

Слайд 22Motor proteins “walk” on microtubules and microfilaments via their heads

acting as “motors”

Слайд 23Kinesin, like myosin, hydrolyzes ATP as it walks
During this process

chemical energy is
transformed into mechanical energy, hence the name motor

protein.

Kinesin, like myosin, hydrolyzes ATP as it walksDuring this process chemical energy istransformed into mechanical energy, hence

Слайд 24MOTOR PROTEINS MOVE VESICLES ON MICROTUBULE TRACKS –
A CONFORMATIONAL

CYCLE THAT HYDROLYZES ATP

Слайд 25MOTOR PROTEINS MOVE VESICLES ON MICROTUBULE TRACKS

Слайд 26Direction of vesicle
Transport on microtubules
FIBROBLAST
NEURON
Movement of pigment granules on

Direction of vesicleTransport on microtubules FIBROBLASTNEURONMovement of pigment granules on MTs

Слайд 27Cilia And Flagella: A Different Form Of Motility

Слайд 28

Слайд 29Dynein provides Motive force
to move one
MT doublet
relative to a
neighboring
MT

doublet

Слайд 30Dynein
Motors
cause
microtubule
sliding in
vitro; these
motors
cause
bending in
an intact
flagellum

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Lecture 20: The Cytoskeleton: Intermediate Filaments and

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Слайд 1Lecture 20:The Cytoskeleton:Intermediate Filaments and MicrotubulesEssentialCell BiologyFourth EditionChapter 17

Слайд 2The Cytoskeleton Includes Dynamic NetworksOf Microfilaments And Microfilaments

Слайд 3The cytoskeleton consists of three major types of filaments plus

many filament-associated proteins including molecular motors Microfilaments – composed of

Слайд 4YPET – MAP R – MT PLUS ENDKERITAN – INTERMEDIATE

FIL.ACTIN – STRESS FIBERSACTININ – STRESS FIBERSVIMENTIN – INTERMEDIATETUBULIN -

Слайд 5IntermediateFilamentsare non-dynamic and structural.They positionthe nucleusand insert into Desmosomesto hold

neighboringcellstogether.

Слайд 6IntermediateFilamentspolymerizeto form strongrope-like fibers. The basic structural unit is a

coiled-coildimer. Thesefibers are symmetric

Слайд 7The inner side of the nuclear envelopeis lined by a

network of intermediatefilaments called lamins. They serve asan anchoring site

Слайд 8Intermediate filament networks flare out from the nucleus and insert

into plasma membrane junctions called desmosomes. Desmosomes connect the intermediate

Слайд 9Microtubules Make Up Dynamic Networks

Слайд 10Microtubules serve four functions:To give shape to the cell.Example: nerve

axons contain numerous micro-tubules along their length. If disrupted the