Questions: Multiple Choice Question Which is found in thin filaments but is not a regulatory protein? Tropomyosin Actin Troponin Myosin

The answer is the second one (B): Actin.

Explanation for each option:

• Tropomyosin: This is a regulatory protein found in thin filaments. It plays a role in regulating muscle contraction by blocking the binding sites on actin molecules.

• Actin: This is a structural protein found in thin filaments. It is not a regulatory protein. Actin forms the backbone of the thin filament and interacts with myosin to facilitate muscle contraction.

• Troponin: This is another regulatory protein found in thin filaments. It works with tropomyosin to regulate the interaction between actin and myosin.

• Myosin: This is not found in thin filaments; it is a motor protein found in thick filaments. Myosin interacts with actin to produce muscle contraction.

In summary, actin is the protein found in thin filaments that is not a regulatory protein.