Biomolecules and enzymes: gel filtration chromatography: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Biomolecules and enzymes: gel filtration chromatography

Sample item

A mixture of proteins of 150 kDa, 66 kDa and 14 kDa is passed through a gel filtration column. In which order do they leave the column?

A66 kDa first, then 14 kDa, then 150 kDaB14 kDa first, then 66 kDa, then 150 kDaCAll three together, since the column separates only by chargeD150 kDa first, then 66 kDa, then 14 kDa

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. 150 kDa first, then 66 kDa, then 14 kDa

Gel filtration (size-exclusion) separates molecules by size. Large molecules cannot enter the pores of the beads, take the shorter path through the column and elute first, while small molecules enter the pores and are delayed. This is the opposite of what happens in SDS-PAGE, where small molecules migrate furthest.

Option by option

A. 66 kDa first, then 14 kDa, then 150 kDa
This order does not follow any property of size; the intermediate protein cannot elute first.
B. 14 kDa first, then 66 kDa, then 150 kDa
This is the order of migration distance in SDS-PAGE, not of elution from a gel filtration column.
C. All three together, since the column separates only by charge
Separation in gel filtration is by size, not by charge, so the proteins do not elute together.
D. 150 kDa first, then 66 kDa, then 14 kDa (correct)
Correct. The largest protein is excluded from the pores and elutes first.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, 150 kDa first, then 66 kDa, then 14 kDa. Gel filtration (size-exclusion) separates molecules by size.

Why is "66 kDa first, then 14 kDa, then 150 kDa" not the answer?

This order does not follow any property of size; the intermediate protein cannot elute first.

Why is "14 kDa first, then 66 kDa, then 150 kDa" not the answer?

This is the order of migration distance in SDS-PAGE, not of elution from a gel filtration column.

Why is "All three together, since the column separates only by charge" not the answer?

Separation in gel filtration is by size, not by charge, so the proteins do not elute together.

What concept does this question test?

It tests Biomolecules and enzymes: gel filtration chromatography in Biochemistry. Large molecules cannot enter the pores of the beads, take the shorter path through the column and elute first, while small molecules enter the pores and are delayed. This is the opposite of what happens in SDS-PAGE, where small molecules migrate furthest.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Biomolecules and enzymes: gel filtration chromatography?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.