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(J) Histology Test 1 > Lecture 6: Cytoskeleton > Flashcards

Lecture 6: Cytoskeleton Flashcards

1
Q

What are the main types of proteins that make up the cytoskeleton?

A

Microfilaments (actin)
Intermediate filaments
Microtubules

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2
Q

What are the characteristics of actin?

A

Diameter: 7nm
Organization: bundles and 3D networks

Bind directly or indirectly to transmembrane protein.

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3
Q

What is monomer of actin called?

A

G-actin (globular)

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4
Q

What is polymerized actin called?

A

F-actin (filamentous)

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5
Q

Describe the polarity of an actin filament

A

Barbed end (positive end): growth occurs more rapidly

Pointed end (negative end): disassembly occurs more rapidly

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6
Q

Describe what happens to an actin filament at high, intermediate, and low cytoplasmic concentrations.

A

High concentrations favors actin filament growth.

Intermediate concentrations result in a dynamic equilibrium between growth and disassembly at the barbed and pointed end respectively; TREADMILLING

Low concentrations favor actin filament disassembly

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7
Q

What does cytochalasin do?

A

Binds the barbed end of actin and prevents elongation.

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8
Q

What does phalloidin do?

A

Binds to actin filaments at different parts and prevents dissociation.

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9
Q

What does spectrin do?

A

Binds the cortical cytoskeleton to the plasma membrane in RBCs.

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10
Q

What does dystrophin do?

A

Binds the cortical cytoskeleton to the plasma membrane.

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11
Q

What do villin and fimbrin do?

A

Forms cross linkages in microvilli.

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12
Q

What do calmodulin and myosin I do?

A

Forms cross-linkages between actin and plasma membrane inn microvilli.

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13
Q

What does alpha-actinin do?

A

Forms cross linkages in stress fibers and connects to protein plasma membrane complexes.

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14
Q

What does filamin do?

A

Forms cross-linkages in actin to for a screen-like gel.

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15
Q

What does thymosin do?

A

Captures actin monomers; prevents polymerization.

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16
Q

What does profilin do?

A

Binds monomers and facilitates exchange of ADP for ATP.

17
Q

What does gelsolin do?

A

Caps actin filaments and destabilizes it. Fragments the filament in high concentration of calcium.

18
Q

What does cofilin do?

A

Disassembles ADP actin at the pointed end.

19
Q

What does arp2/3 do?

A

Initiates growth on the sides of actin filaments; causes branching.

20
Q

What do latrunculins do?

A

Bind G-actin inducing F-actin depolymerization.

21
Q

What are the characteristics of intermediate filaments

A

Diameter: 8-10nm

Provides tensile strength.

Form cytoplasmic network.

Scaffolding to organize internal structures.

22
Q

What is the structure of an intermediate filament?

A

Two polypeptides from a coiled dimer.

Dimers assemble in a staggered antiparallel fashion to form a tetramer.

Tetramers align end to end to form protofilaments.

Eight protofilaments are wound together to form a filament.

23
Q

What are the structure of a microtubule?

A
  • dimer of alpha and beta tubulin
  • dimers line up to form protofilaments
  • 13 protofilaments form a hollow cylinder, microtubule
  • 25 nm
24
Q

Describe how microtubules assemble.

A
  • assembly is more rapid on the plus end and slower on the minus end
  • tubulin-GTP is added to the plus end and hydrolyzed
  • exhibits treadmilling
25
Q

What do colchicine and colecmid do to microtubules?

A

Inhibit polymerization

26
Q

What do vincristine and vinblastine do to microtubules?

A

Inhibit growth; cancer drug

27
Q

What does taxol do to microtubules?

A

Stabilize; cancer drug

28
Q

What are the functions of the cytoskeleton? (7)

A
  • movement
  • support and strength
  • phagocytosis
  • mitotic spindle formation
  • cytokinesis
  • cell-to-cell/matrix adherence
  • shape
29
Q

Myosin I, myosin II, kinesiology, dynein

of heads
Tail binds to:
Head binds to:
Direction of motion:

A
  • 1, 2, 2, 2
  • cell membrane, myosin II, vesicle, vesicle
  • actin, actin, microtubule, microtubule
  • barbed(plus) barbed (plus), plus, minus

(J) Histology Test 1 (9 decks)

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