PHYSIOLOGY
EXCITATION CONTRACTION COUPLING
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Which of the following statements about muscle contraction is FALSE?
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When Ca++ binds to a myosin head, it triggers the formation of a cross-bridge between myosin and actin.
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A troponin molecule that binds a calcium ion weakens its connection to an actin molecule.
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In the resting state, a myosin head is bound to an ADP and a phosphate molecule that have been produced by splitting an ATP molecule.
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Myosin cross-bridges remain in place until the myosin head binds an ATP molecule.
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Explanation:
Detailed explanation-1: -The motion of muscle shortening occurs as myosin heads bind to actin and pull the actin inwards. This action requires energy, which is provided by ATP. Myosin binds to actin at a binding site on the globular actin protein.
Detailed explanation-2: -In addition to binding actin, the myosin heads bind and hydrolyze ATP, which provides the energy to drive filament sliding. This translation of chemical energy to movement is mediated by changes in the shape of myosin resulting from ATP binding.
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