So to synthesize ATP, we have to actually input energy. And the ATP molecules, when they break down, that is an exergonic reaction and energy is released. And every time we break down ATP molecules inside our body, energy is released. And we can use that energy to basically power different types of processes that take place inside our body that require those ATP molecules. So on the other hand, a chemical reaction is said to be endergonic and non spontaneous if a delta g is positive. And ATP synthesis is an example of such an endergonic reaction.