MCAT Biochemistry Question 40: Answer and Explanation
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Question: 40
10. Which of the following methods would be best to separate large quantities of the following proteins? (Note: MM = molar mass)
| Protein | pI | MM |
| Protein A | 6.5 | 28,000 |
| Protein B | 6.3 | 70,000 |
| Protein C | 6.6 | 200,000 |
- A. Ion-exchange chromatography
- B. Size-exclusion chromatography
- C. Isoelectric focusing
- D. Native PAGE
Correct Answer: B
Explanation:
The proteins described in the question differ primarily in their molecular weights. Their pI values are very close, so ion-exchange chromatography, choice (A), is not a good choice. The question specifies a large quantity, which is better processed through chromatography than through electrophoresis—choices (C) and (D)—because the gel can only handle a small volume of protein.