Which of the following is a possible role of enzymes in catalysis?

• A. Changing the overall free energy change of a reaction ($\mathrm{\Delta G}$)
• B. Converting endothermic reactions into exothermic reactions
• C. Lowering the activation energy of a reaction ($E_a$)
• D. Increasing the equilibrium constant of a reaction ($K$_eq)

Answer: (C)

Verified step by step guidance

1. Understand the role of enzymes in catalysis: Enzymes are biological catalysts that speed up chemical reactions without being consumed in the process.
2. Recognize that enzymes do not change the overall free energy change (ΔG) of a reaction. The free energy change is a property of the reactants and products, not the pathway taken.
3. Identify that enzymes cannot convert endothermic reactions into exothermic reactions. The thermodynamics of a reaction are determined by the reactants and products, not the enzyme.
4. Learn that enzymes lower the activation energy of a reaction. This is the energy barrier that must be overcome for reactants to be converted into products. Lowering this barrier increases the rate of the reaction.
5. Understand that enzymes do not increase the equilibrium constant of a reaction. The equilibrium constant is determined by the relative energies of the reactants and products, not the enzyme.