During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a deltaG of -20kcal/mol. If you double the amount of enzyme in the reaction, what will be the deltaG for the new reaction?

Question

BlackTom AI · Accepted Answer

Understanding the question requires recognizing the role of enzymes in a reaction. Enzymes accelerate the rate at which equilibrium is reached but do not alter the thermodynamic driving force, i.e., the Gibbs free energy change (deltaG) of the reaction itself.
Option 1: 40kcal/mol. This would suggest that doubling enzyme changes the sign or magnitude of deltaG to a positive value or reverses the energy landscape. In reality, enzyme concentration does not change deltaG, so this option misinterprets enzyme effect as a change in thermodynamics rather than kinetics.
Option 2: -20kcal/mol. This matches the original deltaG of the reaction. Since deltaG is a thermodynamic property determined by the difference in free energy between products and reactants under standard conditions (and not by the amount of enzyme present), doubling enzyme does not alter this value.
Option 3: -10kcal/mol. This option implies a partial reduction in the magnitude of deltaG, which would require a change in the intrinsic thermodynamics of the reaction, not simply a change in enzyme concentration. Enzymes cannot halve deltaG just by being present in greater amounts.
Option 4: 20kcal/mol. A positive deltaG would indicate a non-spontaneous or endergonic reaction under the given conditions, which contradicts the original thermodynamics of the system. Enzyme quantity does not flip the sign of deltaG.
Option 5: -40kcal/mol. This would double the magnitude in the negative direction, suggesting a stronger thermodynamic drive due to more enzyme, which is incorrect because deltaG is not dependent on enzyme amount.
In summary, the only statement consistent with fundamental biochemistry is that deltaG remains unchanged by simply doubling the amount of enzyme, since enzymes affect rate (kinetics) but not the intrinsic thermodynamic potential of the reaction.

Bio 93 Section CDE 2025 Midterm 2 Practice Exam

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a deltaG of -20kcal/mol. If you double the amount of enzyme in the reaction, what will be the deltaG for the new reaction?

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