Does ATP hydrolysis reaction have a high or low activation energy? I was recently studying about ATP and how it functions as an energy carrier to all biological processes; however, I came across a confusing and paradoxical statement from two sources: (at 7:36) and (the free response question in the bottom of the page) Basically, in the video, it says that ATP hydrolysis has a high activation energy which is why all of the ATP isn't randomly used by the cell processes. And in the free response question, the answer is that ATP hydrolysis has a low activation energy and low free energy making it a spontaneous reaction. A follow up question is: How then does the ATP of the cell used in a selective way to certain processes only? Thanks for your help.

High and low are not very descriptive since they are relative. ATP hydrolysis may have a high activation energy compared to some reactions and low when compared to others. The important point is that the activation energy is sufficiently high enough such that ATP is not rapidly hydrolysed under physiological conditions before it can do useful work. In other words ATP hydrolysis is kinetically unfavourable but thermodynamically favourable. The reaction rate is increased by enzymes (by lowering the activation energy), which couple ATP hydrolysis to other processes to do useful work.

Also, a note on reaction spontaneity: it has nothing to do with activation energy but rather depends on the change in free energy; ATP hydrolysis is spontaneous because it is exergonic.