In order for high force crossbridges to form in contracting skeletal muscle, calcium must
A) bind to calmodulin to phosphorylate the myosin.
B) phosphorylate the tropomyosin which moves it.
C) phosphorylate the troponin to move the tropomyosin.
D) bind to tropomyosin which moves the troponin.
E) bind to troponin which moves the tropomyosin.

Question

Quizplus · Accepted Answer

Calcium ions bind to the troponin molecule, causing conformational changes that move the tropomyosin away from the myosin-binding site on the actin filament. This allows the high-force crossbridge to form between the myosin head and the actin filament, resulting in muscle contraction. Phosphorylation does play a role in muscle contraction, but it is not directly involved in the binding of calcium ions to the troponin molecule.

In Order for High Force Crossbridges to Form in Contracting