Question

question 17
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during the skeletal muscle contraction cycle, what causes the myosin head
to return to its original position?
calcium ions binding to troponin
myosin pulling on actin
tropomyosin covering the myosin - binding site
atp cleavage into adp and inorganic phosphate

Explanation:

In the skeletal muscle contraction cycle, when ATP binds to the myosin head, it causes the myosin head to detach from actin. The cleavage of ATP into ADP and inorganic phosphate provides the energy for the myosin head to return to its original (cocked) position. Calcium ions binding to troponin (option 1) is related to the exposure of myosin - binding sites on actin. Myosin pulling on actin (option 2) is part of the power - stroke phase of muscle contraction. Tropomyosin covering the myosin - binding site (option 3) is related to muscle relaxation (when there is no calcium), not the return of the myosin head to its original position.

Answer:

ATP cleavage into ADP and inorganic phosphate