PHYSIOLOGY
EXCITATION CONTRACTION COUPLING
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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For tropomyosin to be shifted off its position covering the active sites of actin molecules, calcium ions must bind to which structure?
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z-discs
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troponin
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thin filaments
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ryadine receptor
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Explanation:
Detailed explanation-1: -If present, calcium ions bind to troponin, causing conformational changes in troponin that allow tropomyosin to move away from the myosin-binding sites on actin. Once the tropomyosin is removed, a cross-bridge can form between actin and myosin, triggering contraction.
Detailed explanation-2: -When calcium binds to troponin, the structure of troponin is altered. This results in the removal of tropomyosin from myosin binding sites on actin. Thus, as the active site of actin is now available, myosin heads in the muscle are able to bind to the actin. This results in muscle contraction.
Detailed explanation-3: -In order to uncover the active sites on actin, calcium ions must bind to troponin.
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