How does an enzyme affect the activation energy of a biochemical reaction?

• A. It changes the reaction's overall Gibbs free energy change (ΔG) to make the reaction more favorable.
• B. It increases the activation energy to prevent side reactions.
• C. It lowers the activation energy by stabilizing the transition state.
• D. It is consumed during the reaction, providing the energy needed to overcome the activation barrier.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the role of activation energy (Ea) in biochemical reactions. Activation energy is the minimum energy required for reactants to reach the transition state and proceed to products.
2. Step 2: Recognize that enzymes function as biological catalysts, which means they speed up reactions without being consumed in the process.
3. Step 3: Know that enzymes lower the activation energy by stabilizing the transition state, making it easier for reactants to convert into products.
4. Step 4: Clarify that enzymes do not change the overall Gibbs free energy change (\$\(\Delta\) G\$) of the reaction; \$\(\Delta\) G\$ depends on the difference in free energy between reactants and products and remains the same with or without the enzyme.
5. Step 5: Conclude that by lowering the activation energy, enzymes increase the reaction rate without altering the thermodynamic favorability or being consumed during the reaction.