Final answer:
The heavy chain of myosin uses its ATPase region to hydrolyze ATP, storing energy that enables it to bind to actin and perform the power stroke, essential for muscle contraction.
Step-by-step explanation:
The heavy chain of myosin contains 2 important regions: the first acts as an ATPase to convert energy into movement whereas the second binds to actin. The ATPase activity at the binding site on myosin enables the hydrolysis of ATP to ADP and inorganic phosphate, P₁, which provides the energy necessary for the myosin head to change into a cocked position. This stored energy is then used to perform a power stroke by binding to actin and pulling it along, which is fundamental for muscle contraction.
Upon ATP binding, myosin heads dissociate from actin, leading to the conversion of ATP to ADP and P₁. This process allows myosin to adopt a high-energy conformation while remaining attached to the hydrolized ATP. When actin binding sites are accessible, the myosin head forms a cross-bridge with actin and the stored energy is expended as a conformational change, which powers the movement of actin filaments during muscle contraction.