Once calcium bonds to troponin, ..... shifts, which allows the active sites of G-actin to be exposed therefore allowing the formation of crossbridges.

SYNAPTIC PHYSIOLOGY

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Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]

Once calcium bonds to troponin, ____ shifts, which allows the active sites of G-actin to be exposed therefore allowing the formation of crossbridges.

A	myosin
B	actin
C	tropomyosin
D	None of the above

Explanation:

Detailed explanation-1: -(1) Striated muscle in the relaxed state has tropomyosin covering myosin-binding sites on actin. (2) Calcium binds to troponin C, which induces a conformational change in the troponin complex. This causes tropomyosin to move deeper into the actin groove, revealing the myosin-binding sites.

Detailed explanation-2: -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-3: -Upon binding calcium, troponin moves tropomyosin away from the myosin-binding sites on actin (bottom), effectively unblocking it.

Detailed explanation-4: -Calcium binds to troponin, altering its shape. Calcium binding to troponin causes tropomyosin to move away from the active sites on actin. What role does tropomyosin play in the cross bridge cycle? The displacement of tropomyosin exposes the active sites of actin, allowing cross bridges to form.

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