Which is thick filament of muscle

Options

A. Actin
B. Troponin
C. Tropomyosin
D. Myosin.

Answer

To answer the question "Which is the thick filament of muscle?" we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Muscle Structure**:
- Muscle fibers are composed of myofibrils, which contain alternating dark and light bands.

2. **Identifying the Bands**:
- The dark bands in the myofibrils are known as A-bands, which are associated with thick filaments.
- The light bands are known as I-bands, which are associated with thin filaments.

3. **Identifying Thick and Thin Filaments**:
- The thick filament is primarily made up of the protein myosin.
- The thin filament is primarily made up of the protein actin.

4. **Analyzing the Options**:
- **Actin**: This is a thin filament, so it is incorrect.
- **Troponin**: This is a protein associated with actin, not a filament, so it is incorrect.
- **Tropomyosin**: This is also a protein that associates with actin, not a filament, so it is incorrect.
- **Myosin**: This is the thick filament, making it the correct answer.

5. **Conclusion**:
- The thick filament of muscle is **myosin**.

### Final Answer:
The thick filament of muscle is **myosin**.

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