ATPase enzyme needed for muscle contraction is located in myosin.

Explanation:

Muscle contraction is a complex process that involves the interaction between two major proteins, actin and myosin. The ATPase enzyme is an essential component for muscle contraction as it provides the energy required for the movement of myosin along the actin filaments.

Role of ATPase in muscle contraction:

1. Actin and myosin interaction: Muscle contraction occurs when the myosin heads interact with actin filaments, forming cross-bridges. The ATPase enzyme is located on the myosin heads and plays a crucial role in this interaction.

2. Hydrolysis of ATP: The ATPase enzyme hydrolyzes ATP (adenosine triphosphate) into ADP (adenosine diphosphate) and inorganic phosphate (Pi). This hydrolysis reaction releases energy that is used to power the movement of the myosin heads.

3. Cocking of myosin heads: After the hydrolysis of ATP, the myosin heads undergo a conformational change called "cocking." This cocking motion allows the myosin heads to bind to actin and form cross-bridges.

4. Power stroke: Once the myosin heads are bound to actin, the ADP and Pi are released, and the myosin heads undergo a power stroke. During the power stroke, the myosin heads pivot, pulling the actin filaments towards the center of the sarcomere and causing muscle contraction.

5. ATP binding and detachment: At the end of the power stroke, a new ATP molecule binds to the myosin heads, causing them to detach from actin. The ATPase enzyme hydrolyzes the newly bound ATP, providing energy for the myosin heads to reset and prepare for another cycle of muscle contraction.

In summary, the ATPase enzyme located on the myosin heads is responsible for hydrolyzing ATP, providing the energy required for muscle contraction. Without ATPase, the myosin heads would not be able to generate the necessary force for muscle contraction.