Final answer:
The myosin head must bind to an ATP molecule for it to disconnect from the actin molecule.
Step-by-step explanation:
The myosin head must bind to an ATP molecule for it to disconnect from the actin molecule. When the myosin head binds to an ATP molecule, it undergoes a conformational change that allows it to detach from actin. The ATP is then hydrolyzed into ADP and inorganic phosphate, resulting in the re-energized myosin head being in a position for further movement.
For a cross-bridge to disconnect from an actin molecule, an ATP molecule must bind to the myosin head. The cross-bridge cycle is initiated when the myosin head, with ADP and inorganic phosphate (Pi) still attached, binds to actin. After the power stroke, ADP and Pi are released, and then when a new ATP molecule binds to the myosin head, it causes the myosin head to detach from actin.