PHYSIOLOGY
MUSCLE STRUCTURE FUNCTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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ATP molecules prevent calcium from binding to troponin
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calcium ion block actin binding sites on the myosin heads
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the troponin-tropomyosin complex covers the myosin-binding sites on the thin filaments
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actin forms cross bridges with myosin, preventing tropomyosin from sliding over troponin
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Detailed explanation-1: -Tropomyosin is a protein that winds around the chains of the actin filament and covers the myosin-binding sites to prevent actin from binding to myosin.
Detailed explanation-2: -Tropomyosin and troponin prevent myosin from binding to actin while the muscle is in a resting state.
Detailed explanation-3: -In a relaxed muscle, the troponin-tropomyosin complex prevents the myosin heads from binding to the active sites on the actin microfilaments. Troponin also has a binding site for Ca++ ions. These two regulatory proteins work together to respond to calcium and thus “regulate” sarcomere contraction.
Detailed explanation-4: -Actin has binding sites for myosin attachment, but strands of tropomyosin block the binding sites and prevent actin-myosin interactions when the muscles are at rest. Tropomyosin is regulated by troponin, which is regulated by calcium (Ca2+) ions.
Detailed explanation-5: -This model suggests that troponin · tropomyosin in the relaxing position blocks the binding of the myosin cross-bridge to actin.