During ATP hydrolysis used for muscle contraction, which products are released?

• A. ADP
• B. Pi
• C. H+
• D. All of the above

Answer: (D)

In muscle contraction, ATP hydrolysis by the myosin ATPase provides the energy for cross-bridge cycling. When ATP is cleaved, water breaks the terminal phosphate bond, yielding three products: ADP, inorganic phosphate (Pi), and a hydrogen ion (H+). The energy released powers the myosin head’s conformational change (the cocking step) and drives the power stroke that generates force. Pi release is closely tied to that force-generating step, while ADP is released after the stroke, resetting the myosin head for another cycle. The H+ enters the surrounding solution, contributing to local pH changes. So the products released are ADP, Pi, and H+.