# DBT JRF 2022 — Question 46

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Thermodynamics & Reaction Parameters · Difficulty: Medium

## Question

Which one of the following will NOT change upon adding an enzyme to a chemical reaction or changing the concentration of reactants or products? A. ΔG° B. K_eq C. ΔG

## Options

- **A.** A, B
- **B.** B, C
- **C.** A, B, C
- **D.** Only A

## Answer

Option A

## Explanation

Thermodynamic constants: $\Delta G^\circ$ , $K_{eq}$ , and the effect of catalysts: Distinctions: • $\Delta G^\circ$ (standard free energy change): Fixed for a given reaction under standard conditions. Depends ONLY on the reaction, NOT on enzyme or reactant concentrations. • $K_{eq}$ (equilibrium constant): Related to $\Delta G^\circ$ by: $\Delta G^\circ = -RT\ln K_{eq}$ If $\Delta G^\circ$ is constant, $K_{eq}$ is also constant. Enzymes do NOT change $K_{eq}$ . • $\Delta G$ (actual free energy change): Depends on actual concentrations: $\Delta G = \Delta G^\circ + RT\ln Q$ where Q is the reaction quotient. This changes with reactant/product concentrations. Therefore: • $\Delta G^\circ$ and $K_{eq}$ are thermodynamic constants, unchanged by enzyme presence or reactant concentrations. • $\Delta G$ changes with concentrations and departs from $\Delta G^\circ$ .

Source: https://mypyqbuddy.com/questions/which-one-of-the-following-will-not-change-6a104cd5920734408bc0c73d