Question 1

Which of the following statements best describes the role of the centrosome in a eukaryotic cell?

Accepted Answer

It serves as the microtubule organizing center (MTOC), nucleating and stabilizing the minus ends of microtubules.

Question 2

Microtubules are composed of which type of protein subunits?

Accepted Answer

Alpha- and beta-tubulin dimers

Question 3

What is the effect of Taxol on microtubules, and why is it used in chemotherapy?

Accepted Answer

Taxol stabilizes microtubules, blocking cell division and thus inhibiting cancer cell proliferation.

Question 4

Which of the following best explains why kinesin is considered a 'processive' motor protein?

Accepted Answer

Kinesin can take many consecutive steps along a microtubule without dissociating because one head is always firmly bound.

Question 5

During muscle contraction, which molecular event directly generates the 'power stroke'?

Accepted Answer

Release of phosphate ($$Pi) $$from the myosin head after ATP hydrolysis.

Question 6

Which equation correctly represents the hydrolysis of ATP by motor proteins?

Accepted Answer

$$ATP \rightarrow ADP + Pi$$

Question 7

A scientist removes ATP from a cell extract containing organelles and microtubules. What is the expected result regarding organelle movement?

Accepted Answer

Organelle movement will cease because ATP hydrolysis is required for motor protein function.

Question 8

Which of the following statements about actin filaments is TRUE?

Accepted Answer

Actin filaments grow at the plus end and dissociate from the minus end, with ATP hydrolysis occurring after polymerization.

Question 9

Which motor protein is responsible for moving ER tubules towards the periphery of the cell?

Accepted Answer

Kinesin

Question 10

What is the primary difference between the movement of kinesin and myosin II?

Accepted Answer

Kinesin moves along microtubules in a processive manner, while myosin II moves along actin filaments in a non-processive manner.

Question 11

Which of the following best describes the function of actin-binding proteins in cells?

Accepted Answer

They control the behavior and organization of actin filaments, including nucleation, stabilization, and disassembly.

Question 12

Which of the following is NOT a function of the cytoskeleton?

Accepted Answer

Catalyzing ATP hydrolysis for energy production

Question 13

Which statement about microtubule dynamics is correct?

Accepted Answer

Microtubules grow and shrink dynamically due to GTP hydrolysis by tubulin.

Question 14

A mutation prevents the hydrolysis of ATP in myosin heads. What is the most likely effect on muscle contraction?

Accepted Answer

Muscle contraction will be impaired because the power stroke cannot occur without ATP hydrolysis.

Question 15

Which of the following correctly matches a cytoskeletal filament with its associated motor protein?

Accepted Answer

Microtubules — Kinesin

Question 16

Which process is directly blocked by the chemotherapy drug Taxol?

Accepted Answer

Cell division (mitosis)

Question 17

Which of the following is a correct description of the sliding filament mechanism in muscle contraction?

Accepted Answer

Myosin filaments slide past actin filaments, shortening the sarcomere.

Question 18

Which of the following best explains why dynein moves Golgi membranes towards the center of the cell?

Accepted Answer

Dynein moves cargo towards the minus end of microtubules, which is typically located near the cell center.

Question 19

Which of the following is TRUE regarding the nucleotide binding state and affinity of kinesin heads for microtubules?

Accepted Answer

Kinesin heads bound to ATP have high affinity for microtubules, while those bound to ADP have low affinity.

The Cytoskeleton and Molecular Motors: Structure and Function

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