$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} \rightarrow \mathrm{ADP} + \mathrm{P}_i + \text{energy}$$

Question 1

Which of the following best describes the role of the sarcolemma in skeletal muscle fibers?

Accepted Answer

It is the plasma membrane that conducts action potentials into the muscle fiber.

Question 2

During muscle contraction, which change occurs in the sarcomere according to the sliding filament theory?

Accepted Answer

The H zone decreases in width.

Question 3

Which protein is responsible for blocking the myosin binding sites on actin in a relaxed muscle?

Accepted Answer

Tropomyosin

Question 4

A patient with a genetic defect in dystrophin would most likely experience which of the following?

Accepted Answer

Difficulty linking thin filaments to the sarcolemma, leading to muscle weakness

Question 5

Which of the following is a regulatory protein that binds calcium to initiate muscle contraction?

Accepted Answer

Troponin-C

Question 6

What is the correct sequence of events during the sliding filament mechanism of muscle contraction?

Accepted Answer

Myosin heads detach from actin, ATP is hydrolyzed, myosin binds to actin, power stroke occurs

Question 7

Which structural protein provides elasticity and extensibility to the sarcomere by connecting the Z disk to the M line?

Accepted Answer

Titin

Question 8

If a muscle fiber is unable to store sufficient glycogen, which process would be most directly affected?

Accepted Answer

Energy production during muscle contraction

Question 9

Which of the following correctly matches the protein to its function in the sarcomere?

Accepted Answer

Nebulin: stabilizes the position of thin filaments

Question 10

A muscle biopsy reveals a lack of myosin heads in the center of the sarcomere. What is the functional consequence of this arrangement?

Accepted Answer

No cross-bridge formation in the H zone during contraction

Question 11

Which equation best represents the hydrolysis of ATP by the myosin head during muscle contraction?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H}_2\mathrm{O} ightarrow \mathrm{ADP} + \mathrm{P}_i + 	ext{energy}$$

Question 12

Which of the following is NOT a feature associated with the myosin head?

Accepted Answer

Calcium binding site

Question 13

A mutation in the gene encoding actinin would most likely disrupt which aspect of sarcomere structure?

Accepted Answer

Anchoring of thin filaments at the Z line

Question 14

Which of the following statements about the A band in a sarcomere is correct?

Accepted Answer

Its length remains unchanged during muscle contraction.

Question 15

Which protein complex is responsible for the on/off regulation of muscle contraction?

Accepted Answer

Troponin-tropomyosin complex

Question 16

Which of the following best explains why skeletal muscle fibers are multinucleated?

Accepted Answer

Multiple myoblasts fuse during development to form a single muscle fiber.

Question 17

Which of the following is a correct description of the function of satellite cells in skeletal muscle?

Accepted Answer

They aid in repair and regeneration of muscle fibers.

Question 18

Which of the following proteins is found in the thick filament and is essential for force generation during contraction?

Accepted Answer

Myosin

Question 19

During a muscle contraction, which of the following changes occurs in the I band?

Accepted Answer

It decreases in width.

Question 20

Which of the following best describes the arrangement of actin in the thin filament?

Accepted Answer

Double-stranded helix with myosin binding sites

Skeletal Muscle Anatomy: Structure, Proteins, and Sarcomere Function

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