And the answer is because of a high activation energy. So if we take a look at the following reaction going backwards, this here is the activation energy, the barrier energy that is needed, that we must overcome to actually go from the product side to the reactant side. So even though this reaction here, so going from the products to our reactants is thermodynamically favorable, it is not kinetically favorable. And what that means is we have to input a lot of energy to actually overcome this reverse activation barrier. And we simply don't have that much energy under normal conditions inside our cells at a PH of seven and at the normal body temperature, we don't have enough energy for this reaction to actually take place. In fact, to actually break the peptide bond inside our body, we have to use special enzymes that basically decrease this activation barrier.