What is the Myosin Head Bound to When the Muscle

Question

What is the myosin head bound to when the muscle is at rest?
A) ADP plus an associated phosphate
B) tropomyosin
C) troponin
D) ATP
E) actin

Accepted Answer

When the muscle is at rest, the myosin head is bound to tropomyosin, which is a part of the thin filament. This prevents the myosin head from interacting with actin, which is necessary for muscle contraction. ADP plus an associated phosphate and ATP are both energy sources for the myosin head, and troponin is the protein that regulates the movement of tropomyosin during muscle contraction.