Question

Troponin:

• A. Produces sliding movement of microtubules
• B. Contains globular head
• C. Binding to $C{a}^{+2}$ produces skeletal muscle contraction.
• D. Covers the active site of action

Answer 1

The correct option is D Covers the active site of action

Interaction between actin and myosin is prevented by the proteins tropomyosin and troponin. Calcium ions prevent troponin and tropomyosin from blocking contraction, and calcium levels in the resting muscle are low. The calcium level rises rapidly at time of contraction, which stops the troponin and tropomyosin from blocking contraction.
Under resting intracellular levels of calcium, tropomyosin covers the active on actin to which myosin binds in order to generate forces.
So, the correct answer is 'covers the active of action'.