Final answer:
In an enzyme-catalyzed reaction where the product has lower free energy than the substrate, the reaction will favor the formation of the product. Enzymes lower activation energy but do not change the overall free energy change of the reaction, meaning they facilitate but do not reverse reaction direction despite catalyzing both forward and reverse reactions.
Step-by-step explanation:
When considering enzyme-catalyzed reactions, if the difference in free energy between the substrate and product is very large, and the product has much lower energy, it implies that the reaction will proceed more readily in the direction of substrate to product than in the reverse. This is due to the principle that the net direction of a reaction is from higher to lower free energy. Nevertheless, enzymes can catalyze reactions in both directions; the rate at which the reverse reaction occurs might be significantly lower if the product has substantially lower free energy compared to the substrate.
Activation energy is crucial in this context. It is the energy needed to reach the transition state, from which the reaction can proceed to product formation. Enzymes lower the activation energy, making reactions occur more rapidly, but they do not alter the overall free energy change (ΔG) of the reaction. Thus, the direction of a reaction with a large difference in free energy will not be reversed by an enzyme. It can, however, be facilitated to reach equilibrium faster in the preferable direction. This concept is vital for understanding metabolic pathways and reaction kinetics in biological systems.