Question 1

Which of the following best describes the structural organization of a skeletal muscle fiber?

Accepted Answer

A single multinucleated cell containing myofibrils, surrounded by endomysium

Question 2

Which protein is primarily responsible for the contractile function within the sarcomere?

Accepted Answer

Myosin

Question 3

What is the main function of the Z disc in a sarcomere?

Accepted Answer

Anchoring thin filaments and defining the boundaries of a sarcomere

Question 4

Which of the following best describes the sliding-filament mechanism of muscle contraction?

Accepted Answer

Thick and thin filaments slide past each other, shortening the sarcomere

Question 5

Which regulatory protein blocks the myosin-binding sites on actin molecules in a relaxed muscle?

Accepted Answer

Tropomyosin

Question 6

During muscle contraction, which ion binds to troponin to initiate the exposure of myosin-binding sites?

Accepted Answer

$$Ca^{2+}$$

Question 7

Which of the following is a structural protein that helps maintain the alignment of thick filaments in the sarcomere?

Accepted Answer

Titin

Question 8

A mutation in the gene encoding for nebulin would most likely affect which aspect of muscle structure?

Accepted Answer

Stabilization and alignment of thin filaments

Question 9

Which of the following correctly matches the filament type with its primary protein component?

Accepted Answer

Thick filament – myosin

Question 10

If a muscle fiber is unable to produce ATP, which step of the sliding-filament mechanism would be directly affected?

Accepted Answer

Detachment of myosin heads from actin

Question 11

Which of the following best describes the arrangement of myofibrils within a muscle fiber?

Accepted Answer

Parallel bundles extending the length of the cell

Question 12

Which protein complex is responsible for regulating the interaction between actin and myosin during muscle contraction?

Accepted Answer

Troponin-tropomyosin complex

Question 13

A patient presents with muscle weakness due to a defect in the protein titin. Which function is most likely impaired?

Accepted Answer

Elastic recoil and stabilization of thick filaments

Question 14

Which of the following events occurs first during the sliding-filament mechanism?

Accepted Answer

Calcium ions bind to troponin

Question 15

Which of the following is NOT a component of the thin filament?

Accepted Answer

Myosin

Question 16

Which structural protein links the sarcomere to the sarcolemma and helps transmit force to the extracellular matrix?

Accepted Answer

Dystrophin

Question 17

During a muscle contraction, what happens to the H zone?

Accepted Answer

It becomes narrower as thin filaments slide inward

Question 18

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

Accepted Answer

ATP is unavailable, so myosin heads cannot detach from actin

Question 19

Which of the following is a correct sequence of events in the sliding-filament mechanism?

Accepted Answer

Calcium binds to troponin $$\rightarrow$$ tropomyosin shifts $$\rightarrow$$ myosin binds actin $$\rightarrow$$ power stroke

Question 20

Which of the following best describes the role of ATP in muscle contraction?

Accepted Answer

It provides energy for the detachment of myosin heads from actin

Study Guide: Skeletal Muscle Fiber Structure and Function

Study Guide - Practice Questions