6.4.P14

Two students discussing the process of ATP hydrolysis (ATP + H₂O → ADP + P_i) make the following comments:

Justin: “The O-P bond in ATP is called a ‘high-energy bond’ because the energy released when ATP is hydrolyzed is large. That released energy can be used to do useful things in the body that require energy, like making a muscle contract.”

Kim:  “I thought chemical bonds like the O-P bond in ATP could be modeled by a potential energy curve like this (she draws the picture at the right), where r is the distance between the O and the P.  If that’s the case, then breaking the O-P bond in ATP would require me to input energy. I might not have to input much energy to break it, if that O-P happens to be a weak bond, but shouldn’t I have to input at least some energy?”

How did Kim infer from the PE graph that breaking the O-P bond requires an input of energy? Who’s right? Or can you reconcile their statements? (The chemical structures of this process are given if you find that useful.) Note:  This is an essay question.  Your answer will be judged not solely on its correctness, but for its depth, coherence, and clarity.