The thick filaments in a myofibres are formed by the protein

Options

A. Myoglobin
B. Chitin
C. Actin
D. Myosin

Answer

**Step-by-Step Solution:**

1. **Understanding Myofibers**: Myofibers are the basic structural units of muscle tissue. They are long, thread-like structures that make up muscles and are essential for muscle contraction and movement.

2. **Identifying Thick Filaments**: In myofibers, there are two types of filaments: thick and thin filaments. Thick filaments are primarily responsible for muscle contraction.

3. **Composition of Thick Filaments**: The thick filaments are made up of the protein myosin. Myosin is crucial for muscle contraction as it interacts with the thin filaments (which are primarily made of actin) to produce movement.

4. **Function of Myosin**: Myosin not only forms the thick filaments but also plays a role in converting chemical energy (from ATP) into mechanical energy, facilitating muscle contraction.

5. **Differentiating Other Proteins**:
- **Myoglobin**: This is a protein that binds oxygen in muscle cells but does not form thick filaments.
- **Chitin**: This is a polysaccharide found in the exoskeletons of arthropods and is not a protein.
- **Actin**: This is a protein that forms the thin filaments and is involved in muscle contraction but is not responsible for the thick filaments.

6. **Conclusion**: Based on the above understanding, the thick filaments in myofibers are formed by the protein myosin.

**Final Answer**: Myosin

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