ATPase activity in muscle fibre lies with

Options

A. light meromyosin
B. troponin
C. head of heavy meromyosin
D. short arm of heavy meromyosin

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks where ATPase activity lies in muscle fibers. ATPase is an enzyme that catalyzes the hydrolysis of ATP into ADP and inorganic phosphate (Pi), which is crucial for muscle contraction.

2. **Identifying Muscle Fiber Components**: Muscle fibers contain myosin, actin, and various regulatory proteins. Myosin is a motor protein that interacts with actin to facilitate muscle contraction.

3. **Recognizing Myosin Structure**: Myosin is composed of two main parts: light meromyosin and heavy meromyosin. The heavy meromyosin has a globular head that is essential for muscle contraction.

4. **Locating ATPase Activity**: The ATPase activity is specifically associated with the head of the heavy meromyosin. This head binds to ATP, and the ATPase activity hydrolyzes ATP to ADP and Pi, allowing the myosin head to become energized and interact with actin.

5. **Elimination of Incorrect Options**:
- **Light Meromyosin**: This part does not have ATPase activity; it mainly forms the tail of the myosin molecule.
- **Troponin**: This is a regulatory protein that does not have ATPase activity.
- **Short Arm of Heavy Meromyosin**: This part does not contain the ATPase activity either.

6. **Conclusion**: The ATPase activity in muscle fibers lies with the head of heavy meromyosin. This is the correct answer.

**Final Answer**: The ATPase activity in muscle fiber lies with the head of heavy meromyosin.

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