So for us to go from this energy level right over here to this energy level, let's say right over here, we have the input a certain amount of energy. So that means that the peptide bond formation is a process that requires energy. Now where does that energy come from in our body? Well, the energy comes from using ATP molecules. So it turns out that to actually form a peptide bond, we have to use ATP molecules as a result of the fact that the reactants are thermodynamically more stable than our products. So once again, notice that the four reaction which is a dehydrolysis reaction, is thermodynamically unfavorable.