When a muscle fiber is relaxed,why can't myosin bind to actin?
A) ATP is not present
B) the myosin binding site on actin is blocked
C) the myosin head is in the wrong shape for binding
D) the actin is in the wrong orientation for myosin binding
E) the myosin head is 180 degrees from its attachment configuration

Question

Quizplus · Accepted Answer

When a muscle fiber is relaxed, the myosin binding site on actin is covered by the protein tropomyosin, which prevents myosin from binding. This is part of the regulatory mechanism that controls muscle contraction. The presence of ATP, the shape of the myosin head, the orientation of actin, and the attachment configuration of myosin do not directly affect the ability of myosin to bind to actin when the myosin binding site is blocked.

When a Muscle Fiber Is Relaxed,why Can't Myosin Bind to Actin