PHYSIOLOGY
MUSCLE CONTRACTION
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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When actin slides
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When myosin heads bind to actin
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When myosin heads release from actin
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When myosin slides
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Detailed explanation-1: -At the end of the power stroke, the myosin is in a low-energy position. After the power stroke, ADP is released, but the cross-bridge formed is still in place. ATP then binds to myosin, moving the myosin to its high-energy state, releasing the myosin head from the actin active site.
Detailed explanation-2: -The ATP molecule bound to the myosin head is hydrolyzed to produce ADP and an inorganic phosphate. The hydrolysis of ATP releases the energy needed for the myosin head to be ready for another power stroke and bind to another myosin binding site further along the actin filament.
Detailed explanation-3: -ATP is used during relaxation to break the bond between the myosin heads and the actin filament. Additionally, ATP is needed to actively pump calcium ions back into the sarcoplasmic reticulum.
Detailed explanation-4: -Step 2: ATP binding to the myosin head domain induces a small conformational shift in the actin-binding site that reduces its affinity for actin and causes the myosin head to release the actin filament.