Question

during muscle contraction, binding sites for myosin are uncovered by the movement of______.
multiple choice
adp
titin
actin
tropomyosin
troponin

Explanation:

During muscle contraction, tropomyosin covers the myosin - binding sites on actin in a resting state. When calcium ions bind to troponin, it causes a conformational change. This change moves tropomyosin, uncovering the myosin - binding sites on actin. ADP is involved in the cross - bridge cycle (release of myosin head from actin when ATP binds, and ADP is a product during the power stroke), but it does not uncover the binding sites. Titin is a large protein that provides elasticity to muscle fibers. Actin is the thin filament where the binding sites are located, not the molecule that moves to uncover them.

Answer:

tropomyosin