Cytoskeleton Flashcards by Kirilee Wagner

The cytoskeletal system consists of 3 protein filament families including:
A. Kinesin, actin filaments, intermediate filaments
B. Actin filaments, microtubules, intermediate filaments
C. Microtubules, actin filaments, fubulin
D. intermediate filaments, actin filaments, myosin
E. Myosin, dynein, microtubules

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Microtubules are composed of which monomers?

Alpha and beta tubulin

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Microfilaments are composed of which monomers?

G-actin

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Microfilaments bind what form of energy?

ATP

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MTOC stands for?

Microtubule Organising Centre

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Actin structures are assembed and disassembled rapidly, which of the following dictates this assembly and cell function?
A. Activity of MTOC in specific cellular locations
B. Location of cytoskeleton in the cell
C. Expression of microfilaments associated proteins in specific cellular locations
All of the above

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Which of the following are involved in disassembly of actin filaments?
A. Profilin
B. Gelsolin
C. Cofilin
D. B &amp; C

D. B & C

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Profilin promotes

Actin assembly at positive end

Inhibits nucleation

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Function of gelsolin

Sever actin filaments in half, to allow for quicker degradation

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Arp2/3 regulated by..

Nucleiation proteins e.g. WASP

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In the process called actin treadmilling:
A. Myosin proteins cause movement of actin filaments
B. Actin filaments of muscle cells contract
C. Subunits are added to the + end with the - end anchored to the membrane
D. Subunits are simultaneously added & removed from a filament

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Microtubules serve all of the following functions in cells, EXCEPT:
A. They help to control movements of subcellular particles
B. They are the primary structural component of flagella
C. Microtubules mediate the movement of chromosomes during mitosis
Microtubules are the “thick filaments” of sarcomeres
Microtubules are components of centrioles

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Which fibrous component(s) have dynamic instability?
A. Actin filaments
B. Microtubules
C. Intermediate filaments
D. A &amp; B
E. B &amp; C

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Why do intermediate filaments not have dynamic instability?

They are constructed for long-term use

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Which of the following are involved in the disassembly of microtubules?
A. Stathmin
B. Katanin
C. Tau
D. Plectin

B. Katanin

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Role of katanin

Cuts microtubules, allowing quicker disassembly

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Role of tau

Bundles microtubules

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Role of plectin

Links microtubules to intermediate filaments

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Outline the action of taxol in anti-cancer

Stabilises microtubules, forcing the cell to be frozen in metaphase.

Rope-like filament structures formed from 8 protofilaments twisted together and does not have a molecular motor is a characteristic of what cytoskeleton system?

Intermediate filaments

During contraction of a sarcomere
A. Actin filaments are pulled towards the centre of the sarcomere
B. Kinesis head groups bind together
C. Ca++ is released from the cell through exocytosis
D. Microtubules slide relative to each other
E. None of the above

During the contraction of a sarcomere, binding of ATP to myosin causes:
A. The myosin head group to bind to the actin filament
B. Release of the myosin head group from the actin filament
C. A change in the shape of myosin head group
D. Sliding of the actin and myosin filaments relative to each other

Which molecular motors allow intracellular transport on microtubules?
A. Kinesin
B. Myosin
C. Dynein
D. A &amp; C
E. None of the above

``` What is similar between focal adhesions and hemidesmosomes? A. They both use actin filaments B. They both use intermediate filaments C. They both use anchor proteins D. They both are very stable E. All of the above ```

C. They both use anchor proteins

What are the basic mechanisms of cell migration? A. Triggered by signals from outside the cell B. Actin-myosin based movement C. Requires attachments to outside to pull agains D. Ability to move all cell content E. All of the above

How many proteofilaments in a microtubule wall/ring?

Describe the structure of a microtubule.

Hollow tube with a wall consisting of 13 proteofilaments

Outline 4 functions of microtubules

Cytoplasmic: - organisation and maintenance of animal cell shape and polarity - chromosome movements - intracellular transport, trafficking and movement of organelles Axonemal: cell motility

Outline the 3 functions of cytoplasmic microtubules

Organisation and maintenance of animal cell shape and polarity Chromosome movements Intracellular transport, trafficking and movement of organelles

What is the function of axonemal microtubules?

Cell motility

What are the functions of microfilaments (actin)?

``` Muscle contraction Cell locomotion Cytoplasmic streaming Cytokinesis Maintenance of animal cell shape Intracellular transport/trafficking ```

Describe the structure of intermediate filaments

8 protofilaments joined end to end with staggered overlaps

Describe the structure of microfilaments

2 intertwined chains of F-actin

Outline the function of intermediate filaments

Structural support Maintenance of animal cell shape Formation of nuclear lamina and scaffolding Strengthening of nerve cell axons (neurofilament protein) Keeping muscle fibres in register (desmin)

How is actin polymerisation rate limited?

Trimer formation

Where is alpha actin found?

Muscle cells

Where is beta and gamma actin found?

Non-muscle cells

Actin filaments that are held together by the cross-linking protein fimbrin are not contractile. This is probably because: A. fimbrin is a large protein that binds to several actin filaments and resists contraction. B. the very tight packing of actin filaments by this small protein excludes myosin II filaments and other large proteins. C. fimbrin arranges the actin filaments into gel-like networks in which myosin II activity does not produce contraction. D. fimbrin arranges the actin filaments in parallel bundles in which all the plus ends point to the same direction. E. the very weak cross-linking by this protein cannot convert myosin II activity into a coherent contraction.

B. The very tight packing of actin filaments by this small protein excludes myosin II filaments and other large proteins.

``` In lamellipodia, actin polymerization is nucleated by ...(1), while depolymerization is catalyzed by ...(2). A. (1) Arp 2/3 complex; (2) gelsolin B. (1) formin; (2) cofilin C. (1) formin; (2) gelsolin D. (1) Arp 2/3 complex; (2) cofilin E. (1) formin; (2) capping protein ```

D.(1) Arp 2/3 complex; (2) cofilin

In lamellipodia, actin polymerization is nucleated by ____ while depolymerization is catalyzed by ____.

Arp2/3 complex | Cofilin

In contrast to growing microtubules, shrinking microtubules: A. have a GTP cap at their plus end. B. have strong lateral interactions at their plus ends. C. have curved protofilaments at their plus ends. D. cannot be rescued unless microtubule-stabilizing proteins bind and inhibit depolymerization. E. All of the above.

C. have curved protofilaments at their plus ends.

``` In which of the following structures are actin–myosin II bundles regulated by the troponin complex? A. Stress fiber B. Circumferential belt C. Contractile ring D. Adherens junction E. None of the above ```

E. None of the above

The gamma-tubulin ring is to microtubules what ____ is to actin filaments

Arp2/3 complex

``` Which of the following cytoskeletal filaments are abundant in an animal cell nucleus? A. Spectrin filaments B. Septins C. Intermediate filaments D. Microtubules E. Microfilaments ```

C. Intermediate filaments

Which cytoskeletal filaments are abundant in an animal cell nucleus?

Intermediate filaments