When Calcium Ion Binds To Troponin. A) tropomyosin moves out of the groove between the actin molecules. When calcium binds troponin, certain changes happen inside muscle cell membranes where they become depolarized which leads to contraction.
B) tropomyosin moves into the groove between the helical actin strands. For skeletal muscle contraction, calcium binds to troponin to uncover actin binding sites. Troponin c binds to calcium ions to produce a conformational change in tni;