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. So we can see that if we know what the gives free energy value is of some particular reaction, we know whether or not that reaction is actually spontaneous. Now, another important fact that you have to know about this quantity gives free energy is gives free energy only depends on the energy, the free energy value of the product and the free energy value of the reactants. So if we know what the free energy of the product is and the free energy of the reactants, all we have to do is subtract the two to find that gives free energy.