Which of the following explains why ATP hydrolysis to ADP + Pi provides energy for muscle contraction?

• A. Breaking the high-energy phosphate bond lowers the free energy of the system and the released energy drives conformational changes in contractile proteins.
• B. ATP hydrolysis increases cellular pH dramatically, which stimulates all muscle enzymes to work faster and therefore produces contraction without additional chemical work.
• C. The released inorganic phosphate binds irreversibly to myosin forming a permanent cross-bridge that maintains contraction until the phosphate is depleted.
• D. Hydrolysis of ATP converts it into glycogen directly, which is then oxidized to provide heat that makes muscles contract more effectively during exercise.

Answer: (A)