Chapter_16_Cytoskeleton_Flashcards

Question 1

What are the three main cytoskeletal elements in eukaryotic cells?

Answer 1

Actin filaments, microtubules, intermediate filaments.

Question 2

What is the primary function of actin filaments?

Answer 2

Determine cell shape and facilitate movement.

Question 3

Describe the process of actin filament treadmilling.

Answer 3

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

Question 4

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

Answer 4

It nucleates branched actin filament structures.

Question 5

How does profilin influence actin filament elongation?

Answer 5

It promotes actin monomer addition at the plus end.

Question 6

What is dynamic instability in microtubules?

Answer 6

Alternation between growth and shrinkage due to GTP cap loss.

Question 7

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

Answer 7

Intermediate filaments lack polarity and are made of fibrous subunits.

Question 8

How does the centrosome function in microtubule organization?

Answer 8

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

Question 9

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

Answer 9

Intermediate filaments are more stable and resist deformation better.

Question 10

How does actin filament nucleation differ from microtubule nucleation?

Answer 10

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

Question 11

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

Answer 11

Regulate actin filament assembly and cell polarity.

Question 12

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

Answer 12

Rac promotes lamellipodia formation; Rho promotes stress fiber formation.

Question 13

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

Answer 13

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

Question 14

True or False: Intermediate filaments exhibit polarity.

Answer 14

False.

Question 15

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

Answer 15

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

Question 16

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

Answer 16

True.

Question 17

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

Answer 17

A trimer stabilizes weak interactions, allowing rapid polymerization.

Question 18

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

Answer 18

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

Question 19

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

Answer 19

Coiled-coils bundled laterally for mechanical strength.

Question 20

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

Answer 20

Reduced lamellipodia formation, impairing migration.

Question 21

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

Answer 21

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

Question 22

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

Answer 22

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

Question 23

Why is dynamic instability important during mitosis?

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

Increases depolymerization, disrupting cytoskeletal functions.

Question 26

How does filamin deficiency affect cellular movement?

Answer 26

Impairs actin network crosslinking, reducing cell motility.

Question 27

What happens during actin-based Listeria movement?

Answer 27

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

Question 28

How do actin filaments and microtubules cooperate during vesicle transport?

Answer 28

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

Question 29

Why are accessory proteins essential for cytoskeletal function?

Answer 29

They regulate filament dynamics, stability, and interactions.

Question 30

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

Answer 30

True.

Question 31

What are microtubules made of?

Answer 31

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

Question 32

What is the primary function of intermediate filaments?

Answer 32

Provide mechanical strength to cells.

Question 33

What motor proteins are associated with actin filaments?

Answer 33

Myosin.

Question 34

What is the role of kinesin motor proteins?

Answer 34

Move cargo toward the microtubule plus end.

Question 35

What is the role of dynein motor proteins?

Answer 35

Move cargo toward the microtubule minus end.

Question 36

What cellular structure organizes microtubules?

Answer 36

Centrosome.

Question 37

What are lamellipodia?

Answer 37

Sheet-like actin-rich protrusions for cell migration.

Question 38

What are filopodia?

Answer 38

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

Question 39

What is the role of GTP in microtubule dynamics?

Answer 39

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

Question 40

What is catastrophe in microtubule dynamics?

Answer 40

Transition from growth to shrinkage.

Question 41

What is rescue in microtubule dynamics?

Answer 41

Transition from shrinkage to growth.

Question 42

How do thymosin and profilin regulate actin polymerization?

Answer 42

Thymosin prevents polymerization; profilin promotes polymerization.

Question 43

How does cofilin affect actin filaments?

Answer 43

It severs older filaments, promoting disassembly.

Question 44

What nucleates actin filaments?

Answer 44

ARP2/3 complex and formins.

Question 45

What is the primary nucleator of microtubules?

Answer 45

γ-TuRC (gamma-tubulin ring complex).

Question 46

Where are intermediate filaments found in epithelial cells?

Answer 46

Anchored to desmosomes and hemidesmosomes.

Question 47

What cytoskeletal structure forms the mitotic spindle?

Answer 47

Microtubules.

Question 48

What is the function of the nuclear lamina?

Answer 48

Provide structural support to the nucleus.

Question 49

What accessory protein organizes actin into web-like networks?

Answer 49

Filamin.

Question 50

What is the function of spectrin in red blood cells?

Answer 50

Supports the plasma membrane.

Question 51

True or False: All cytoskeletal filaments are dynamic.

Answer 51

True.

Question 52

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

Answer 52

False.

Question 53

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

Answer 53

False.

Question 54

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

Answer 54

True.

Question 55

What happens if a cell lacks functional centrosomes?

Answer 55

Microtubule organization and mitotic spindle formation are impaired.

Question 56

How would a mutation in keratin affect skin cells?

Answer 56

Increased fragility, leading to blistering under mechanical stress.

Question 57

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

Answer 57

Impaired muscle contraction and cytokinesis.

Question 58

How does a loss of filamin affect immune cells?

Answer 58

Reduced ability to form lamellipodia, impairing migration.

Question 59

Compare microtubule and actin filament polarity.

Answer 59

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

Question 60

How do stress fibers differ from lamellipodia?

Answer 60

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

Question 61

Compare WASP and WAVE proteins in actin nucleation.

Answer 61

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