$$\text{Creatine phosphate} + \text{ADP} \rightarrow \text{Creatine} + \text{ATP}$$

Question 1

Which of the following best describes the role of calcium ions ($$Ca^{2+}) in $$skeletal muscle contraction?

Accepted Answer

Calcium ions bind to troponin, causing a conformational change that exposes myosin binding sites on actin.

Question 2

During the crossbridge cycle, what event directly triggers the power stroke?

Accepted Answer

Release of inorganic phosphate ($$P_i) $$from the myosin head

Question 3

Which process is responsible for the removal of $$Ca^{2+}$$ from the cytosol to end muscle contraction?

Accepted Answer

Active transport by the sarcoplasmic reticulum $$Ca^{2+}-$$ATPase pump

Question 4

What is the primary source of ATP during the first few seconds of intense skeletal muscle activity?

Accepted Answer

Phosphocreatine breakdown

Question 5

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

Calcium leaks into the sarcoplasm, but ATP is unavailable to release myosin from actin.

Question 6

Which equation correctly represents the reaction catalyzed by creatine kinase in muscle cells?

Accepted Answer

$$	ext{Creatine phosphate} + 	ext{ADP} ightarrow 	ext{Creatine} + 	ext{ATP}$$

Question 7

A patient with a genetic defect in the SERCA pump would most likely experience which symptom?

Accepted Answer

Prolonged muscle contraction due to delayed relaxation

Question 8

Which step in the crossbridge cycle is directly dependent on the presence of ATP?

Accepted Answer

Release of myosin from actin

Question 9

During anaerobic metabolism in muscle cells, what is the fate of pyruvate?

Accepted Answer

It is converted to lactate.

Question 10

Which of the following best describes the latent period in excitation-contraction coupling?

Accepted Answer

The time between the muscle fiber action potential and the onset of contraction

Question 11

Which of the following is TRUE regarding the sliding filament theory?

Accepted Answer

Myosin heads pull actin filaments toward the center of the sarcomere, causing muscle shortening.

Question 12

Which metabolic pathway provides the greatest yield of ATP per glucose molecule in skeletal muscle?

Accepted Answer

Aerobic metabolism (citric acid cycle and electron transport chain)

Question 13

What is the function of troponin in skeletal muscle contraction?

Accepted Answer

Troponin binds calcium, causing a conformational change that moves tropomyosin away from actin's myosin binding sites.

Question 14

Which of the following is a direct consequence of ATP depletion in muscle cells?

Accepted Answer

Permanent attachment of myosin to actin (rigor)

Question 15

Which of the following best explains why muscle fibers store glycogen?

Accepted Answer

Glycogen provides a rapid source of glucose for ATP production during muscle activity.

Question 16

Which of the following events occurs FIRST during excitation-contraction coupling in skeletal muscle?

Accepted Answer

Generation of an action potential in the muscle fiber

Question 17

Which of the following is NOT a function of ATP in skeletal muscle contraction?

Accepted Answer

Binding to troponin to initiate contraction

Question 18

During prolonged, low-intensity exercise, which metabolic pathway is most important for ATP production in skeletal muscle?

Accepted Answer

Aerobic metabolism of fatty acids (beta-oxidation)

Question 19

Which of the following best describes the role of the sodium-calcium exchanger in skeletal muscle relaxation?

Accepted Answer

It passively exchanges intracellular calcium for extracellular sodium, contributing to calcium removal.

Question 20

A muscle fiber is unable to relax after contraction. Which of the following is the most likely cause?

Accepted Answer

Impaired function of the $$Ca^{2+}-$$ATPase pump in the sarcoplasmic reticulum

Muscle Contraction and ATP Supply in Skeletal Muscle

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