Question 1

Which of the following best describes the function of the sarcoplasmic reticulum (SR) in skeletal muscle cells?

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 2

A patient is experiencing muscle weakness due to a defect in acetylcholine (ACh) receptors at the neuromuscular junction. Which process is most directly impaired?

Accepted Answer

Initiation of an action potential in the muscle fiber membrane (sarcolemma).

Question 3

During intense exercise, when oxygen is limited, which pathway is primarily used by muscle cells to generate ATP?

Accepted Answer

Anaerobic glycolysis in the sarcoplasm.

Question 4

Which of the following correctly matches a muscle cell adaptation with its function?

Accepted Answer

Glycosomes: store glucose for ATP production.

Question 5

What is the role of myoglobin in skeletal muscle cells?

Accepted Answer

It binds and stores oxygen for use during aerobic ATP production.

Question 6

Which of the following events occurs immediately after acetylcholine binds to its receptor on the sarcolemma?

Accepted Answer

Opening of sodium ($$\mathrm{Na^+}) $$gated channels and influx of $$\mathrm{Na^+}$$ into the muscle cell.

Question 7

A muscle cell is unable to relax after contraction. Which malfunction is most likely responsible?

Accepted Answer

Failure of the sarcoplasmic reticulum to reabsorb $$\mathrm{Ca$$^{2+}$$}$$ ions.

Question 8

Which equation best represents the net ATP yield from glycolysis of one glucose molecule in the absence of oxygen?

Accepted Answer

$$\mathrm{C_6H_{12}O_6$} \rightarrow 2\ \mathrm{C_3H_6O_3} + 2\ \mathrm{ATP}$$

Question 9

Why do athletes sometimes take creatine supplements, and what is a potential risk?

Accepted Answer

To increase creatine phosphate stores for rapid ATP regeneration; risk includes kidney strain.

Question 10

Which of the following best explains why muscle cells contain many mitochondria?

Accepted Answer

To meet the high energy demand for ATP production during contraction.

Question 11

A toxin blocks the reuptake of acetylcholine at the neuromuscular junction. What is the most likely effect on muscle contraction?

Accepted Answer

Prolonged muscle contraction due to continuous stimulation.

Question 12

Which structure in the muscle cell is directly responsible for propagating the action potential deep into the fiber?

Accepted Answer

T-tubules (transverse tubules)

Question 13

During the power stroke of muscle contraction, which molecule is hydrolyzed to provide energy?

Accepted Answer

ATP

Question 14

Which of the following best describes the sequence of events at the neuromuscular junction leading to muscle contraction?

Accepted Answer

Motor neuron releases acetylcholine $$\rightarrow$$ acetylcholine binds to sarcolemma receptors $$\rightarrow$$ sodium channels open $$\rightarrow$$ action potential spreads.

Question 15

A genetic mutation causes a deficiency in myoglobin within muscle cells. Which symptom would most likely be observed during prolonged exercise?

Accepted Answer

Early muscle fatigue due to reduced oxygen storage.

Question 16

Which of the following is the correct order of structures from largest to smallest in skeletal muscle organization?

Accepted Answer

Muscle $$\rightarrow$$ Fascicle $$\rightarrow$$ Muscle fiber $$\rightarrow$$ Myofibril $$\rightarrow$$ Sarcomere

Question 17

If the sodium-potassium pump in the sarcolemma is inhibited, what is the most immediate effect on muscle cell function?

Accepted Answer

The cell cannot repolarize after an action potential, impairing repeated contractions.

Question 18

Which of the following best explains why carbon dioxide ($$\mathrm{CO_2$}) is $$produced during aerobic respiration in muscle cells?

Accepted Answer

It is a byproduct of the citric acid cycle in the mitochondria.

Question 19

A patient with a genetic defect in the enzyme that phosphorylates glucose upon entry into the muscle cell would have difficulty with which process?

Accepted Answer

Trapping glucose in the cell as glucose-6-phosphate for glycolysis.

Review of Muscle Tissue, ATP, and the Neuromuscular Junction

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