Why must tropomyosin cover the thin filament in just the right position before the muscle can relax?
A) It covers the myosin-binding sites and, if left exposed, will allow the myosin to bind and pull.
B) Without tropomyosin in the correct position, calcium cannot be released.
C) It is needed in the proper location, or ATP cannot be used.
D) It has a particular binding place that facilitates the removal of calcium.

Question

Quizplus · Accepted Answer

Tropomyosin covers the myosin-binding sites on the actin filaments, preventing myosin from binding and initiating muscle contraction. When calcium ions are released, they bind to another protein called troponin, which causes tropomyosin to move out of the way, allowing myosin to bind and initiate muscle contraction. If tropomyosin is not covering the myosin-binding sites in the absence of calcium, myosin can still bind and cause muscle contraction, preventing relaxation.

Why Must Tropomyosin Cover the Thin Filament in Just the Right