PHYSIOLOGY
MUSCLE CONTRACTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Which of the following statement(s) is/are true about the role of ATP during muscle contraction?I) Energizing the power stroke of the myosin cross bridge.II) Disconnecting the myosin cross bridge from the binding site on actin at the conclusion of a power stroke.III) Opening myosin binding sites on actin
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Only I
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I and II
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I, II and III
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Only II
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Explanation:
Detailed explanation-1: -ATP is responsible for cocking (pulling back) the myosin head, ready for another cycle. When it binds to the myosin head, it causes the cross bridge between actin and myosin to detach. ATP then provides the energy to pull the myosin back, by hydrolysing to ADP + Pi.
Detailed explanation-2: -ATP binding to myosin during the contractile cycle results in myosin detachment from actin, and energy liberated from subsequent ATP hydrolysis is then used to drive the next contractile cycle. ATP is also used to lower myoplasmic calcium levels during muscle relaxation.
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