How does the changing state of ATP-binding on myosin influence sarcomere contraction?

Question

What will be an ideal response?

Answer 1

In a relaxed sarcomere, myosin heads have bound ATP molecules and are in a low-energy conformation. Removing a phosphate group (Pi) from a bound ATP energizes a myosin head in a manner analogous to stretching a spring. The myosin head remains in a high-energy conformation, with bound ADP and phosphate, until a signal from the nervous system excites the muscle. When this signal arrives, myosin heads attach to actin and this attachment releases a phosphate group from myosin and triggers a power stroke. Like a stretched spring returning to its original shape, a myosin head snaps back toward the sarcomere center. As it does, it pulls the attached thin filament along with it. During the power stroke, a myosin head releases bound ADP. Afterward, the head can bind to a new molecule of ATP and return to its low-energy conformation.