Question

question 1
0.75 pts
the role of tropomyosin in skeletal muscles indicates which of the following?
tropomyosin is the chemical that activates the myosin heads.
tropomyosin promotes inhibition via blocking the active binding site on actin to prevent engaging the myosin molecules.
tropomyosin serves as a contraction inhibitor by blocking the actin binding sites on the myosin molecules.
tropomyosin is the receptor for the motor neuron neurotransmitter.

Explanation:

Tropomyosin is a protein that wraps around actin filaments. In the resting state of skeletal muscle, it blocks the myosin - binding sites on actin. When calcium ions bind to troponin (another protein complex), tropomyosin shifts, and the myosin - binding sites on actin are exposed, allowing myosin heads to bind and muscle contraction to occur.

• The chemical that activates myosin heads is ATP (adenosine triphosphate), not tropomyosin. So the first option is incorrect.
• Tropomyosin blocks the binding site on actin (not on myosin), so the third option is incorrect.
• The receptor for the motor neuron neurotransmitter (acetylcholine) is on the motor end - plate (a part of the muscle fiber membrane), not tropomyosin. So the fourth option is incorrect.

Answer:

Tropomyosin promotes inhibition via blocking the active binding site on actin to prevent engaging the myosin molecules.