Which of the following most accurately describes the effect of decreasing Ca²⁺ concentration on sarcomere activity? A) troponin is deactivated and tropomyosin covers the actin binding site B) tropomyosin is deactivated and troponin covers the actin binding site C) myosin no longer hydrolyzes ATP and detaches from actin D) myosin no longer binds ATP and recocks into an upright position

Question

Quizplus · Accepted Answer

Decreasing the concentration of Ca²⁺ means that there is less calcium ions available to bind to troponin, which normally causes a conformational change in troponin that moves tropomyosin away from the myosin binding site on actin. With less troponin activated, tropomyosin remains covering the actin binding site, preventing myosin from attaching and initiating muscle contraction.

Which of the Following Most Accurately Describes the Effect of Decreasing