Question 1

Which of the following best explains why muscle fibers cannot store large amounts of ATP for future contractions?

Accepted Answer

The demand for ATP during contraction is so high that it would be impossible to store enough ATP in advance; instead, ATP is generated as needed.

Question 2

A patient presents with elevated levels of creatine kinase (CK) in their blood. What does this most likely indicate?

Accepted Answer

The patient has suffered muscle damage, causing CK to leak into the bloodstream.

Question 3

During peak muscle activity, which metabolic process becomes the primary source of ATP, and what is a major drawback of this process?

Accepted Answer

Anaerobic glycolysis; it leads to lactate and hydrogen ion accumulation, causing metabolic acidosis.

Question 4

Which of the following equations correctly represents the reaction catalyzed by creatine kinase during muscle contraction?

Accepted Answer

$$\mathrm{ADP} + \mathrm{Creatine~Phosphate} \rightarrow \mathrm{ATP} + \mathrm{Creatine}$$

Question 5

A muscle fiber at rest primarily generates ATP through which process, and what substrate does it mainly use?

Accepted Answer

Aerobic metabolism using fatty acids absorbed from the circulation.

Question 6

Why does glycolysis become a significant source of ATP during intense, short-duration exercise?

Accepted Answer

Because oxygen supply is limited, and glycolysis can proceed without oxygen.

Question 7

Which of the following best describes the Cori cycle?

Accepted Answer

The shuttling of lactate from muscle to liver, where it is converted to glucose and returned to muscle.

Question 8

Calculate the total number of ATP molecules generated from one glucose molecule if both pyruvate molecules produced by glycolysis are fully oxidized in the mitochondria. Show your reasoning.

Accepted Answer

2 ATP from glycolysis + 15 ATP per pyruvate (2 pyruvate) = 32 ATP

Question 9

Which hormone would most likely increase the rate of energy consumption in both resting and active skeletal muscles?

Accepted Answer

Thyroid hormones

Question 10

A marathon runner is observed to continue breathing heavily for several minutes after finishing a race. What physiological process best explains this phenomenon?

Accepted Answer

The body is repaying the oxygen debt (excess post-exercise oxygen consumption) to restore ATP, CP, and glycogen levels.

Question 11

Which of the following statements about heat production during muscle activity is correct?

Accepted Answer

During peak exertion, muscle fibers capture about 30% of energy as ATP and lose 70% as heat.

Question 12

Which of the following is a direct consequence of hydrogen ion accumulation in muscle fibers during anaerobic glycolysis?

Accepted Answer

Lowered intracellular pH, which impairs enzyme function and muscle contraction.

Question 13

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

Accepted Answer

Glycogen provides a readily available source of glucose for ATP production during muscle contraction.

Question 14

Which of the following scenarios would most likely lead to premature muscle fatigue?

Accepted Answer

Wearing tight clothing that restricts blood flow to the muscles.

Question 15

Which of the following best explains why aerobic metabolism is considered more efficient than anaerobic glycolysis in muscle fibers?

Accepted Answer

Aerobic metabolism produces more ATP per glucose molecule than anaerobic glycolysis.

Question 16

Which hormone is most directly responsible for stimulating the synthesis of contractile proteins and the enlargement of skeletal muscles?

Accepted Answer

Testosterone

Question 17

During the recovery period after intense exercise, what is the fate of most lactate produced in muscle fibers?

Accepted Answer

It is converted to pyruvate in the liver, then used to synthesize glucose.

Question 18

Which of the following best describes the main function of creatine phosphate in muscle fibers?

Accepted Answer

To rapidly regenerate ATP from ADP during the initial seconds of muscle contraction.

Question 19

A patient with a metabolic disorder cannot efficiently convert lactate to glucose in the liver. Which process would be most directly impaired?

Accepted Answer

The Cori cycle

Question 20

Which of the following best explains why fit athletes continue to breathe heavily after exercise has stopped?

Accepted Answer

To repay the oxygen debt required to restore muscle and liver energy reserves.

Muscle Energy Metabolism: Mechanisms of ATP Production and Recovery in Skeletal Muscle

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