AQA A-Level PE Energy Systems Practice Exam

Energy release from ATP comes when a molecule-specific enzyme hydrolyzes the terminal phosphate bond, converting ATP to ADP and inorganic phosphate and releasing usable energy. The enzyme that does this hydrolysis is ATPase, which powers many cellular processes including muscle contraction through the energy released during ATP breakdown. Lactate dehydrogenase acts on lactate and pyruvate, not ATP. ATP synthase, by contrast, builds ATP from ADP and Pi using a proton gradient, so it consumes energy rather than releases it. Cytochrome oxidase is part of the electron transport chain, transferring electrons to oxygen and helping maintain the gradient, but it does not hydrolyze ATP.