If ATP is present, why do actin and myosin not spontaneously interact with each other in the absence of nerve stimulation? Select all that apply. A) ATP is blocked by an ATPase in the absence of Ca²⁺. B) Myosin and actin require Ca²⁺ to interact. C) ATP is bound to the myosin binding site on actin. D) The actin-binding site for myosin is blocked by troponin/tropomyosin complex.

Question

Quizplus · Accepted Answer

In the absence of nerve stimulation, the actin-binding site for myosin is blocked by the troponin/tropomyosin complex, which prevents interaction between actin and myosin. While ATP is necessary for muscle contraction, its presence alone is not enough to initiate the interaction between actin and myosin in the absence of Ca2+. Therefore, choices A, B, and C are not correct.

If ATP Is Present, Why Do Actin and Myosin Not