Question 1

Which of the following best describes the primary function of dynein in eukaryotic cells?

Accepted Answer

It powers the sliding of microtubules in cilia and flagella, generating bending motion.

Question 2

A mutation disrupts the function of the protein nexin in cilia. Which cellular process would be most directly affected?

Accepted Answer

The ability of cilia to generate a coordinated bending motion.

Question 3

Which of the following statements about the sliding filament model of muscle contraction is correct?

Accepted Answer

Thin filaments slide past thick filaments, with no change in the length of either filament.

Question 4

Which of the following best explains why cardiac muscle cells contract in a coordinated manner?

Accepted Answer

They are joined by intercalated discs containing gap junctions that allow depolarization to spread.

Question 5

A scientist observes a eukaryotic cell with motile appendages that have a '9 + 2' arrangement of microtubules. What structure is being observed?

Accepted Answer

Flagellum

Question 6

Which of the following steps in the muscle contraction cycle is directly triggered by the binding of ATP to myosin?

Accepted Answer

The detachment of myosin from actin.

Question 7

Which of the following is a key difference between kinesin and myosin II function?

Accepted Answer

Kinesin operates alone or in small numbers for long-distance transport, while myosin II operates in large arrays for short-distance movement.

Question 8

A patient has a genetic defect that prevents the phosphorylation of myosin light chains in smooth muscle. Which process would be most directly impaired?

Accepted Answer

The activation of myosin for cross-bridge cycling with actin.

Question 9

Which of the following best describes the role of integrins during cell migration?

Accepted Answer

They connect the extracellular matrix to actin filaments inside the cell, forming focal adhesions.

Question 10

During fast axonal transport, which motor protein is responsible for moving cargo toward the cell body (retrograde transport)?

Accepted Answer

Cytoplasmic dynein

Question 11

Which of the following is true regarding the regulation of skeletal muscle contraction?

Accepted Answer

Troponin binds calcium, causing tropomyosin to shift and expose myosin-binding sites on actin.

Question 12

Which of the following best explains why primary cilia are non-motile?

Accepted Answer

They have a '9 + 0' microtubule arrangement and lack the central pair.

Question 13

A drug inhibits the function of the protein titin in skeletal muscle. What is the most likely effect on muscle contraction?

Accepted Answer

Thick filaments would not be anchored to the Z lines, leading to misalignment during contraction.

Question 14

Which of the following best describes the processivity of kinesin?

Accepted Answer

Its ability to move long distances along a microtubule before detaching.

Question 15

Which of the following events occurs FIRST during the contraction cycle in skeletal muscle?

Accepted Answer

Hydrolysis of ATP, energizing the myosin head.

Question 16

Which of the following is a function of myosin V in eukaryotic cells?

Accepted Answer

Transport of vesicles and organelles along actin filaments.

Question 17

Which of the following best explains the role of radial spokes in the axoneme of cilia and flagella?

Accepted Answer

They translate the sliding of microtubules into bending of the axoneme.

Question 18

Which of the following is a direct result of the activation of myosin light-chain kinase (MLCK) in smooth muscle cells?

Accepted Answer

Phosphorylation of myosin light chains, enabling cross-bridge cycling with actin.

Question 19

Which of the following best describes the function of cytoplasmic streaming in plant cells?

Accepted Answer

It is an actomyosin-dependent movement of cytoplasm, facilitating the distribution of nutrients and organelles.

Cellular Movement: Motility and Contractility

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