The active sites on actin molecules are usually covered up by other molecules. What is the critical material required to uncover the active sites on the actin molecules that will then bind to myosin heads?
A) ATP
B) calcium
C) oxygen
D) vitamin A
E) titin

Question

Quizplus · Accepted Answer

Calcium ions are critical for uncovering the active sites on actin molecules. When calcium levels increase in the muscle cell, it binds to troponin, causing a conformational change that moves tropomyosin away from the active sites on actin, allowing myosin heads to bind to actin and initiate muscle contraction.

The Active Sites on Actin Molecules Are Usually Covered Up