Question

When a muscle is stimulated to contract, myosin heads walk along actin filaments in repeated cycles of attachment and detachment. Which of the following represents a correct description of the events in this cycle?

A. Myosin binds to actin, ATP is hydrolyzed, and myosin undergoes a conformational change to pull actin.
B. Myosin releases ADP and inorganic phosphate, leading to the power stroke and movement of the myosin head.
C. Myosin binds ATP, causing it to detach from actin.
D. The binding of calcium ions initiates the release of myosin from actin.

Answer 1

When a muscle is stimulated to contract, the myosin head attaches to actin and initiates the power stroke. During the power stroke, the myosin head bends with the release of ADP and inorganic phosphate. Another ATP then causes the cross-bridge to detach and return actin to the cocked configuration.

Step-by-step explanation:

When a muscle is stimulated to contract, the myosin head forms a cross-bridge with actin, which initiates the power stroke. During the power stroke, the myosin head bends with the release of ADP and inorganic phosphate. Another ATP then binds to the myosin head, causing the cross-bridge to detach from actin and returning myosin to the cocked configuration.