During the crossbridge cycle in a skeletal muscle, the next step after a myosin head binds...

During the crossbridge cycle in a skeletal muscle, the next step after a myosin head binds to actin is that the myosin head
a. changes conformation in the power stroke.
b. unbinds from the actin.
c. binds to calcium.
d. contributes to rigor mortis.

Expert Solution

Answer : “a” changes confirmation in the power stroke.

Explanation: In resting stage of the muscle tropomycin covers the active site of actin, this prevents the cross bridge formation between myosin and actin.

Binding of ATP to the myosin changes the angle of myosin head and it is ready to bind to the actin site.In this state myosin is at high energy level(the ATP is hydrolysed to ADP and inorganic phosphate)

The contraction of muscles is initiated by binding of calcium ions to troponin leading to the exposure(troponin removes tropomycin from the active site) of active site of actin, the myosin head fills the gap,inorganic phosphate is released and myosin forms a cross bridge with actin. As soon as myosin binds actin it loses energy and there is a conformational change in myosin.since myosin spends the energy, it moves through the power stroke and pulls actin filament toward the M line leading to shortening of sarcomere and the muscle contracts.

gladiator answered 6 months ago

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