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BMS 612 Exam 3 > Chapter_16_Cytoskeleton_Flashcards > Flashcards

Chapter_16_Cytoskeleton_Flashcards

1
Q

What are the three main cytoskeletal elements in eukaryotic cells?

A

Actin filaments, microtubules, intermediate filaments.

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2
Q

What is the primary function of actin filaments?

A

Determine cell shape and facilitate movement.

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3
Q

Describe the process of actin filament treadmilling.

A

Actin monomers add at the plus end (ATP-bound) and dissociate at the minus end (ADP-bound).

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4
Q

What role does the ARP2/3 complex play in actin filament dynamics?

A

It nucleates branched actin filament structures.

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5
Q

How does profilin influence actin filament elongation?

A

It promotes actin monomer addition at the plus end.

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6
Q

What is dynamic instability in microtubules?

A

Alternation between growth and shrinkage due to GTP cap loss.

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7
Q

What is the structural difference between intermediate filaments and other cytoskeletal elements?

A

Intermediate filaments lack polarity and are made of fibrous subunits.

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8
Q

How does the centrosome function in microtubule organization?

A

It acts as the main microtubule organizing center (MTOC).

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9
Q

Compare the stability of intermediate filaments to actin filaments and microtubules.

A

Intermediate filaments are more stable and resist deformation better.

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10
Q

How does actin filament nucleation differ from microtubule nucleation?

A

Actin nucleation forms trimers, while microtubule nucleation requires γ-tubulin complexes.

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11
Q

What is the role of Rho family GTPases in cytoskeletal dynamics?

A

Regulate actin filament assembly and cell polarity.

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12
Q

How do small GTPases like Rac and Rho differently affect actin organization?

A

Rac promotes lamellipodia formation; Rho promotes stress fiber formation.

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13
Q

Explain the concept of ‘critical concentration’ in filament polymerization.

A

The concentration of subunits at which polymerization and depolymerization rates are equal.

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14
Q

True or False: Intermediate filaments exhibit polarity.

A

False.

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15
Q

Compare the roles of CapZ and ARP2/3 in actin filament dynamics.

A

CapZ caps the plus end, preventing elongation; ARP2/3 promotes branching.

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16
Q

True or False: Microtubules depolymerize faster at a GDP-bound end.

A

True.

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17
Q

Describe the mechanism of actin filament nucleation as shown in the diagram.

A

A trimer stabilizes weak interactions, allowing rapid polymerization.

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18
Q

How do γ-tubulin ring complexes (γ-TuRCs) contribute to microtubule nucleation?

A

They cap the minus end and provide a template for assembly.

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19
Q

What structural arrangement do intermediate filaments adopt according to the diagram?

A

Coiled-coils bundled laterally for mechanical strength.

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20
Q

What would happen to cell motility if ARP2/3 was non-functional?

A

Reduced lamellipodia formation, impairing migration.

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21
Q

How does a mutation in the tau protein affect microtubule stability in neurons?

A

Leads to aggregation and destabilization, associated with Alzheimer’s.

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22
Q

If cofilin activity is inhibited, how would it affect actin filament turnover?

A

Reduced disassembly at the minus end, leading to filament accumulation.

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23
Q

Why is dynamic instability important during mitosis?

A

It allows microtubules to rapidly reorganize to form the mitotic spindle.

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24
Q

How do motor proteins like dynein and kinesin coordinate intracellular transport?

A

Dynein moves cargo toward the minus end; kinesin moves cargo toward the plus end.

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25
Q

Predict the effect of a drug that stabilizes GDP-tubulin on microtubules.

A

Increases depolymerization, disrupting cytoskeletal functions.

26
Q

How does filamin deficiency affect cellular movement?

A

Impairs actin network crosslinking, reducing cell motility.

27
Q

What happens during actin-based Listeria movement?

A

ActA protein activates ARP2/3, propelling the bacterium forward.

28
Q

How do actin filaments and microtubules cooperate during vesicle transport?

A

Actin facilitates local movement; microtubules manage long-distance transport.

29
Q

Why are accessory proteins essential for cytoskeletal function?

A

They regulate filament dynamics, stability, and interactions.

30
Q

True or False: Both treadmilling and dynamic instability depend on nucleotide hydrolysis.

A

True.

31
Q

What are microtubules made of?

A

Tubulin heterodimers (α-tubulin and β-tubulin).

32
Q

What is the primary function of intermediate filaments?

A

Provide mechanical strength to cells.

33
Q

What motor proteins are associated with actin filaments?

A

Myosin.

34
Q

What is the role of kinesin motor proteins?

A

Move cargo toward the microtubule plus end.

35
Q

What is the role of dynein motor proteins?

A

Move cargo toward the microtubule minus end.

36
Q

What cellular structure organizes microtubules?

A

Centrosome.

37
Q

What are lamellipodia?

A

Sheet-like actin-rich protrusions for cell migration.

38
Q

What are filopodia?

A

Thin, finger-like projections made of bundled actin filaments.

39
Q

What is the role of GTP in microtubule dynamics?

A

GTP-tubulin promotes polymerization; GDP-tubulin promotes depolymerization.

40
Q

What is catastrophe in microtubule dynamics?

A

Transition from growth to shrinkage.

41
Q

What is rescue in microtubule dynamics?

A

Transition from shrinkage to growth.

42
Q

How do thymosin and profilin regulate actin polymerization?

A

Thymosin prevents polymerization; profilin promotes polymerization.

43
Q

How does cofilin affect actin filaments?

A

It severs older filaments, promoting disassembly.

44
Q

What nucleates actin filaments?

A

ARP2/3 complex and formins.

45
Q

What is the primary nucleator of microtubules?

A

γ-TuRC (gamma-tubulin ring complex).

46
Q

Where are intermediate filaments found in epithelial cells?

A

Anchored to desmosomes and hemidesmosomes.

47
Q

What cytoskeletal structure forms the mitotic spindle?

A

Microtubules.

48
Q

What is the function of the nuclear lamina?

A

Provide structural support to the nucleus.

49
Q

What accessory protein organizes actin into web-like networks?

A

Filamin.

50
Q

What is the function of spectrin in red blood cells?

A

Supports the plasma membrane.

51
Q

True or False: All cytoskeletal filaments are dynamic.

A

True.

52
Q

True or False: Actin filaments can only polymerize at the plus end.

A

False.

53
Q

True or False: Intermediate filaments require ATP or GTP for assembly.

A

False.

54
Q

True or False: Kinesin and dynein can move along the same microtubule simultaneously.

A

True.

55
Q

What happens if a cell lacks functional centrosomes?

A

Microtubule organization and mitotic spindle formation are impaired.

56
Q

How would a mutation in keratin affect skin cells?

A

Increased fragility, leading to blistering under mechanical stress.

57
Q

What effect would blocking myosin II activity have on a cell?

A

Impaired muscle contraction and cytokinesis.

58
Q

How does a loss of filamin affect immune cells?

A

Reduced ability to form lamellipodia, impairing migration.

59
Q

Compare microtubule and actin filament polarity.

A

Both have plus and minus ends; microtubules grow at the plus end faster.

60
Q

How do stress fibers differ from lamellipodia?

A

Stress fibers are contractile bundles; lamellipodia are protrusions for movement.

61
Q

Compare WASP and WAVE proteins in actin nucleation.

A

Both activate ARP2/3; WASP works in filopodia, WAVE in lamellipodia.

BMS 612 Exam 3 (6 decks)

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