Which of the following statements regarding myosin in skeletal muscle is TRUE?
A)Myosin cross-bridge heads contain two binding sites,one for actin and one for tropomyosin.
B)Myosin is an ATPase.
C)The rate of ATP hydrolysis by myosin is the same in all types of skeletal muscle.
D)All of the myosin cross-bridge heads in a thick filament are oriented and rotate in the same direction.
E)Troponin covers the binding site on myosin molecules until Ca²⁺ binds to troponin to remove it from its blocking position.

Question

Quizplus · Accepted Answer

Myosin is an ATPase enzyme, which means it can break down ATP into ADP and phosphate to release energy for muscle contraction. Option A is incorrect because myosin cross-bridge heads contain only one binding site for actin, not for tropomyosin. Option C is incorrect because the rate of ATP hydrolysis varies with the type of skeletal muscle fiber. Option D is incorrect because the myosin cross-bridge heads in a thick filament are oriented and rotate in opposite directions. Option E is incorrect because troponin, not tropomyosin, covers the binding site on the actin molecule until Ca²⁺ binds to troponin to move tropomyosin away and expose the binding site.

Which of the Following Statements Regarding Myosin in Skeletal Muscle