$$\mathrm{ATP} \rightarrow \mathrm{ADP} + \mathrm{P_i} + \text{energy}$$

Question 1

Which of the following statements best describes the structural polarity of actin filaments?

Accepted Answer

Actin filaments have a plus end and a minus end, with the plus end growing faster.

Question 2

A mutation in the gene encoding nuclear lamin proteins is most likely to affect which cellular structure or function?

Accepted Answer

The structural support of the nuclear envelope.

Question 3

Which cytoskeletal element is primarily responsible for the separation of chromosomes during mitosis?

Accepted Answer

Microtubules

Question 4

A scientist observes a cell with defective vesicle transport. Which motor protein and cytoskeletal element are most likely involved?

Accepted Answer

Kinesin and microtubules

Question 5

Which of the following best explains why microtubules exhibit 'dynamic instability'?

Accepted Answer

They alternate between phases of growth and rapid shrinkage due to GTP hydrolysis.

Question 6

Which cytoskeletal element is most important for resisting mechanical stress in skin cells and is a major component of hair and nails?

Accepted Answer

Intermediate filaments

Question 7

During cytokinesis in animal cells, which cytoskeletal elements and proteins are directly involved in pinching the cell into two daughter cells?

Accepted Answer

Actin filaments and myosin

Question 8

A patient with progeria has a mutation in a gene encoding a nuclear lamin. What is the most likely cellular consequence?

Accepted Answer

Abnormal nuclear envelope structure and premature aging symptoms

Question 9

Which of the following best describes the structure of a microtubule?

Accepted Answer

A hollow tube composed of α- and β-tubulin heterodimers

Question 10

Which of the following equations correctly represents the hydrolysis of ATP by a motor protein such as kinesin or myosin?

Accepted Answer

$$\mathrm{ATP} ightarrow \mathrm{ADP} + \mathrm{P_i} + 	ext{energy}$$

Question 11

Which of the following is a key difference between eukaryotic and prokaryotic flagella?

Accepted Answer

Eukaryotic flagella are composed of microtubules arranged in a '9+2' axoneme, while prokaryotic flagella are rigid rods made of flagellin.

Question 12

A researcher disrupts the centrosome in an animal cell. Which process is most likely to be directly affected?

Accepted Answer

Organization and growth of microtubules

Question 13

Which of the following best explains the role of dynein in cilia and flagella movement?

Accepted Answer

Dynein hydrolyzes ATP to 'walk' along microtubule doublets, causing bending of the axoneme.

Question 14

Which cytoskeletal element is most directly involved in cytoplasmic streaming in plant cells?

Accepted Answer

Actin filaments

Question 15

A cell is observed to have a meshwork of filaments supporting its nuclear envelope. Which protein is most likely a major component of this meshwork?

Accepted Answer

Nuclear lamin

Question 16

Which of the following best describes the function of intermediate filaments?

Accepted Answer

They maintain cell shape by resisting tension and provide mechanical strength.

Question 17

Which of the following is true regarding the nucleoside substrate used by actin filaments and microtubules?

Accepted Answer

Actin filaments use ATP, while microtubules use GTP.

Question 18

A cell is treated with a drug that prevents GTP hydrolysis in microtubules. What is the most likely effect on microtubule dynamics?

Accepted Answer

Microtubules will become more stable and less likely to undergo catastrophe.

Question 19

Which of the following best explains why actin filaments can form both bundles and cross-linked networks?

Accepted Answer

Actin filaments are composed of two twisted strands with binding sites for cross-linking proteins.

The Cytoskeleton: Structure and Function Inside the Cell

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