A. The large protein will be eluted first

B. The small protein will be eluted first

C. Both large and small will elute at the same time

D. The small protein with high charge will be eluted first

Gel filtration chromatography separates proteins based on size, with larger proteins eluting first due to their exclusion from gel pores.

This MCQ’s correct answer is A. The large protein will be eluted first, a key concept for exams like GATE Life Sciences.

Correct Answer

A. The large protein will be eluted first

Option Analysis

Gel filtration (size exclusion chromatography) uses porous beads where proteins travel through a column with buffer.

• A. The large protein will be eluted first: Large proteins cannot enter bead pores, so they follow the shortest path (void volume) and exit quickest.

• B. The small protein will be eluted first: Incorrect—small proteins enter pores, take longer paths, and elute later.

• C. Both large and small will elute at the same time: Wrong, as elution strictly follows size order, not simultaneous.

• D. The small protein with high charge will be eluted first: No—separation is size-based only; charge affects ion-exchange, not gel filtration.

Gel filtration chromatography elution order determines protein separation in purification, vital for biochemistry students preparing GATE Life Sciences. This technique relies on molecular size, not charge or affinity.

Principle of Gel Filtration

Porous beads (e.g., Sephadex) form the matrix. Large molecules are excluded from pores, eluting in void volume first; small ones diffuse in, delaying elution.

Elution volume correlates inversely with size: bigger proteins mean earlier peaks.

Why Large Proteins Elute First

Large proteins skirt beads externally for a direct path. Small proteins explore pores, increasing path length by up to 2-3x. Calibration curves plot log(molecular weight) vs. elution volume for accuracy.

Common Misconceptions

Students confuse it with electrophoresis (small migrates faster). Here, no electric field—purely steric exclusion. Charge (option D) is irrelevant.

GATE Exam Relevance

This PYQ tests core purification knowledge. Practice with standards like thyroglobulin (670 kDa, elutes first) vs. cytochrome c (12 kDa, last).

Ideal for protein desalting or oligomer analysis in molecular biology labs.