Thin myofilaments are made up of

Options

A. Actin, tropomyosin and meronyosin
B. Tubulin and dynein
C. Heavy meromyosin and light meromyosin
D. Actin, troponin and tropomyosin

Answer

**Step-by-Step Text Solution:**

1. **Understanding Myofilaments**: Myofilaments are the basic units of muscle contraction and are categorized into two types: thick and thin myofilaments.

2. **Composition of Thin Myofilaments**: Thin myofilaments are primarily composed of the protein actin.

3. **Additional Proteins**: In addition to actin, thin myofilaments also contain two other important proteins: tropomyosin and troponin.

4. **Role of Tropomyosin and Troponin**: Tropomyosin serves as a regulatory protein that blocks the binding sites on actin for myosin during muscle relaxation. Troponin is a complex of three proteins that bind to calcium ions and help regulate muscle contraction by moving tropomyosin away from the binding sites on actin when calcium is present.

5. **Conclusion**: Therefore, thin myofilaments are made up of actin, tropomyosin, and troponin.

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