Question

In the resting muscle fiber, tropomyosin partially covers

• A. Calcium-binding sites on troponin
• B. Actin binding sites on myosin
• C. Myosin binding sites on actin
• D. Calcium-binding sites on actin

Answer 1

The correct option is C

Myosin binding sites on actin

The correct option is C.

Explanation of the correct option:

1. Tropomyosin is a protein found in the actin filaments in muscles.
2. When the muscle is at rest, the tropomyosin molecule covers the binding site of the actin molecule where interaction with myosin occurs.

Explanation of the incorrect options:

Option A:

Calcium-binding sites interact with myosin and help in contraction.

Option B:

On contraction of the muscle, the tropomyosin is displaced troponin, allowing the interaction of actin with myosin.

Option D:

On an increase in calcium level in the cell, calcium binds to actin filaments.

Final answer: In the resting muscle fiber, tropomyosin partially covers Myosin-binding sites on actin.