Which statement about ATP hydrolysis energy transfer is true?

• A. It stores energy for long-term use
• B. It always acts as a catalyst
• C. It consumes energy that must be spent
• D. It powers endergonic reactions by coupling with them

Answer: (D)

Energy transfer from ATP hydrolysis works by coupling the energy released when ATP is converted to ADP and inorganic phosphate to reactions that would not proceed on their own. That exergonic step provides the free energy needed to drive endergonic processes, making the overall reaction favorable. In cells, this coupling drives activities like biosynthesis, active transport, and mechanical work by changing substrates through phosphorylation or fueling conformational changes in proteins. ATP itself isn’t a long-term energy store—fat and glycogen store energy more stably—and ATP hydrolysis isn’t a catalyst; it’s the energy source that enables other reactions to occur. It also doesn’t consume energy; it releases energy to power other tasks. So the true statement is that ATP hydrolysis powers endergonic reactions by coupling with them.