MCAT Biochemistry Question 41: Answer and Explanation
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Question: 41
11. Which amino acids contribute most significantly to the pI of a protein?
I. Lysine
II. Glycine
III. Arginine
- A. I only
- B. I and II only
- C. I and III only
- D. II and III only
Correct Answer: C
Explanation:
The overall pI of a protein is determined by the relative number of acidic and basic amino acids. The basic amino acids arginine, lysine, and histidine, and the acidic amino acids aspartic acid and glutamic acid will therefore contribute most significantly. Glycine’s side chain is a hydrogen atom, so it will have the least contribution of all the amino acids.