# DBT JRF 2022 — Question 95

Exam: DBT JRF 2022 · Section: B · Topic: Biochemistry › Size Exclusion Chromatography · Difficulty: Medium

## Question

Given below are two statements one is labelled as Assertion A and the other is labelled as Reason R: Assertion A: In size exclusion chromatography, larger proteins elute earlier and smaller proteins elute later. Reason R: When matrices like sephadex are used, the partitioning of protein molecules between liquid and solid phases is a function of protein size. In the light of the above statements, choose the correct answer from the options given below:

## Options

- **A.** Both A and R are true and R is the correct explanation of A
- **B.** Both A and R are true and R is not the correct explanation of A
- **C.** A is true but R is false
- **D.** A is false but R is true

## Answer

Option A

## Explanation

Size exclusion chromatography (SEC): both statements correct: Size exclusion chromatography (also called gel filtration) separates proteins by molecular size: • Larger proteins: EXCLUDED from the pores of the gel beads → travel only through the void volume → ELUTE FIRST (shorter retention time). • Smaller proteins: ENTER the pores → take longer to traverse the column → ELUTE LATER. Statement A: 'Larger proteins elute first in SEC' — TRUE ✔ Statement R: 'Separation is size-dependent because proteins partition between the stationary (pore) phase and the mobile (interstitial) phase' — TRUE, and this correctly EXPLAINS statement A. ✔ This is an Assertion-Reason question where BOTH are true and R is the correct explanation of A. Answer: Both A (large molecules elute first) and R (partitioning is size-dependent) are correct; R explains A.

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