# DBT JRF 2022 — Question 23

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Enzyme Reaction Coordinate & Energy Landscape · Difficulty: Medium

## Question

The energy landscape or the energy of a reaction: A ⇌ B Along its reaction coordinate follows the following pattern: ![figure](https://res.cloudinary.com/dxil5euku/image/upload/v1779453123/pyq/6a104cb5920734408bc0c6d8/DBTJRF22-IMGB23.png) Which one of the following statements are true?

## Options

- **A.** The rate at which A changes to B is independent of E1
- **B.** The rate at which B converts to A is determined by E3
- **C.** The rate at which A converts to B is determined by E2
- **D.** The rate at which B converts to A is independent of E3

## Answer

Option B

## Explanation

Energy landscape of reaction A ⇌ B: For the reaction coordinate profile shown: • E1 = energy barrier from A to transition state (determines rate of A → B forward reaction) • E2 = energy of product B above transition state reference (not a common convention) • E3 = energy barrier from B back to transition state (determines rate of B → A reverse reaction) The rate of a reaction depends on the ACTIVATION ENERGY (energy barrier) for that direction: • Rate of $B \rightarrow A$ is determined by E3 (the energy from B's ground state up to the transition state). • Rate of $A \rightarrow B$ is determined by E1. From the answer key: 'Rate at which B converts to A is determined by E3' — this is the correct statement about energy barriers determining reaction rates. Answer: The rate at which B converts to A is determined by E3 (Option 2).

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