MCAT Organic Chemistry Question 177: Answer and Explanation

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Question: 177

12. Given a solution of insulin (molecular weight = 5.8 kD) and titin (molecular weight = 3816 kD), which chromatographic technique would be the most effective for separating out usable molecules of titin?

  • A. Thin-layer chromatography
  • B. Ion-exchange chromatography
  • C. Affinity chromatography
  • D. Size-exclusion chromatography

Correct Answer: D

Explanation:

Because this solution is composed of a much larger molecule and a much smaller molecule, size-exclusion chromatography would effectively remove the smaller insulin molecule into the fraction retained in the column and allow the titin to be eluted. Affinity chromatography, choice (C), could also be used, but comes with a risk of rendering the titin unusable; the eluent run through an affinity chromatography column often binds to the target molecule.

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