Head of _has ATP ase activity.

Answer

**Step-by-Step Solution:**

1. **Identify the Components of Muscle Fibers**: Muscle fibers consist of two main types of protein filaments: actin and myosin. Actin filaments are thin, while myosin filaments are thick.

2. **Focus on Myosin Filaments**: The question specifically asks about the ATPase activity associated with the head of a filament. Myosin filaments are known to have this activity.

3. **Understand Myosin Structure**: Myosin is a polymerized protein, meaning it is made up of multiple monomer units. These monomer units are referred to as meromyosin.

4. **Distinguish Parts of Myosin**: The myosin filament has two distinct parts: a head and a tail. The head part is crucial for its function.

5. **Identify ATPase Activity**: The globular head of the myosin filament possesses ATPase activity. This means that it can hydrolyze ATP, which is essential for muscle contraction.

6. **Binding Sites**: The head of the myosin also has a binding site for ATP, allowing it to interact with ATP molecules during the contraction process.

7. **Conclusion**: Therefore, the head of myosin has ATPase activity.

**Final Answer**: The head of myosin has ATPase activity.

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