MUSCLE PHYSIOLOGY

Detailed explanation-1: -Tropomyosin is a long, double-stranded, helical protein that is wrapped about the long axis of the actin backbone (Figure 2-8, D). Tropomyosin serves to block the active site on actin, thereby inhibiting actin and myosin from binding under resting conditions.

Detailed explanation-2: -Calcium is essential for muscle contraction because it allows for the removal of tropomyosin from the actin binding sites.

Detailed explanation-3: -Tropomodulin: a cytoskeletal protein that binds to the end of erythrocyte tropomyosin and inhibits tropomyosin binding to actin.

Detailed explanation-4: -Tropomyosin binds to troponin to form a troponin-tropomyosin complex. The troponin-tropomyosin complex prevents the myosin “heads” from binding to the active sites on the actin microfilaments. Troponin also has a binding site for Ca++ ions.