But if we add an enzyme the energy value of the reactants and products will not actually change. Now, if the thermodynamics of the products and reactants is not changed by an enzyme, what is actually changed? Well, recall that the kinetics of the chemical reaction is determined by the energy of the transition state. And the transition state is this transient molecule, transient stage that exists between the reactants and our products. Now, what exactly will the transition state look like when we go from the reactants to the products? Well, we have a single elementary, a single step elementary reaction in which on the reactants side we have a bond between A and B.