Which of the following is an active ATPase?

The globular head of myosin is an active ATPase enzyme. Myosin is a motor protein responsible for muscle contraction, and its globular head region plays a crucial role in this process.

• ATPase Activity: The globular head of myosin has ATPase activity, which means it can hydrolyse ATP (adenosine triphosphate) into ADP (adenosine diphosphate) and inorganic phosphate (Pi). This ATPase activity provides the energy needed for muscle contraction.
• Binding Sites for ATP: The globular head has binding sites for ATP molecules. When ATP binds to myosin, it causes a conformational change in the myosin head, leading to its energised state.
• Binding Sites for Actin: The globular head of myosin also has binding sites for actin, another protein involved in muscle contraction. During muscle contraction, myosin heads attach to actin filaments, forming cross-bridges.
• Cross-Bridge Cycle: The cross-bridge cycle is a series of steps that involve the myosin heads binding to actin, using the energy from ATP hydrolysis to change their conformation and generate force, and then releasing from actin as ADP and Pi are released. This cycle repeats, causing the sliding of actin filaments past myosin filaments, resulting in muscle contraction.