The free energy change of hydrolysis of sucrose into glucose and fructose is ΔG = - 7
kcal/mol. When the enzyme sucrase is added to the reaction mixture, what happens to the ΔG of the reaction?

Question

BlackTom AI · Accepted Answer

Question restatement: The free energy change of hydrolysis of sucrose into glucose and fructose is ΔG = -7 kcal/mol. When the enzyme sucrase is added, what happens to the ΔG of the reaction?

Option a: 'The ΔG is decreased' — This is incorrect. A catalyst like an enzyme lowers the activation energy barrier, not the overall free energy change of the reaction. The thermodynamics (ΔG) are determined by the difference in energy between reactants and products, not by catalysts.

Option b: 'The ΔG is increased' — This is incorrect for the same fundamental reason as above: enzymes do not alter the thermodynamic favorability (ΔG) of the reaction; they affect kinetics, not the equilibrium free energy.

Option c: 'The ΔG remains the same' — This is correct. Enzymes accelerate the rate of the reaction by stabilizing transition states and lowering the activation energy, but they do not change the overall ΔG of hydrolysis. The energetics from reactants to products stay the same (−7 kcal/mol in this case).

Option d: 'The ΔG is equal to the activation energy of sucrase' — This is incorrect. ΔG and the activation energy (Ea) are distinct concepts: ΔG is the change in free energy from reactants to products, while Ea is the energy barrier to reach the transition state. An enzyme lowers Ea but does not set ΔG to Ea.

Summary: Enzymes modify reaction rates by lowering activation energy without altering the intrinsic thermodynamics of the reaction, so the only option that aligns with this is that the ΔG remains the same.

The free energy change of hydrolysis of sucrose into glucose and fructose is ΔG = - 7 kcal/mol. When the enzyme sucrase is added to the reaction mixture, what happens to the ΔG of the reaction?

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