Question

Myosin comprises what per cent of the myofibrilar proteins?

• A. 25%
• B. 35%
• C. 45%
• D. 55%

Hint:

Myofibrillar protein composition: Myosin accounts for $\approx 55\%$ and Actin accounts for $\approx 20\text{--}25\%$.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Skeletal muscle proteins are categorized into sarcoplasmic, myofibrillar (salt-soluble), and stromal (connective tissue) proteins.

Step 2: Detailed Explanation:
Myofibrillar proteins constitute the contractile apparatus of muscle cells.
Myosin is the largest thick filament protein, making up approximately $55\%$ (50--55%) of the total myofibrillar protein fraction.
Actin accounts for approximately $20\text{--}25\%$, tropomyosin $\approx 5\%$, troponin $\approx 5\%$, and titin/nebulin constitute the remainder.

Step 3: Final Answer:
Thus, myosin comprises 55% of myofibrillar proteins.