Which is required for cross‑bridge detachment during muscle contraction?

Which is required for cross‑bridge detachment during muscle contraction?

• A. ATP
• B. Calcium
• C. Acetylcholine
• D. Myosin

Answer: (A)

Detachment of the myosin head from actin requires ATP binding. When ATP binds to the myosin head, its affinity for actin drops and the cross-bridge releases. After detachment, ATP is hydrolyzed to ADP and Pi, which re-energizes the head for another cycle. Calcium is needed to expose actin’s binding sites so cross-bridges can form, and acetylcholine at the neuromuscular junction triggers the contraction signal, but the actual release of the cross-bridge hinges on ATP binding. Myosin is the motor protein that does the binding and power stroke, and without ATP the cross-bridges would remain attached (rigor).

Detachment of the myosin head from actin requires ATP binding. When ATP binds to the myosin head, its affinity for actin drops and the cross-bridge releases. After detachment, ATP is hydrolyzed to ADP and Pi, which re-energizes the head for another cycle. Calcium is needed to expose actin’s binding sites so cross-bridges can form, and acetylcholine at the neuromuscular junction triggers the contraction signal, but the actual release of the cross-bridge hinges on ATP binding. Myosin is the motor protein that does the binding and power stroke, and without ATP the cross-bridges would remain attached (rigor).