MCAT Biochemistry Question 10: Answer and Explanation
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Question: 10
10. Which of these amino acids has a chiral carbon in its side chain?
I. Serine
II. Threonine
III. Isoleucine
- A. I only
- B. II only
- C. II and III only
- D. I, II, and III
Correct Answer: C
Explanation:
Every amino acid except glycine has a chiral α-carbon, but only two of the 20 amino acids—threonine and isoleucine— also have a chiral carbon in their side chains as well. Thus, the correct answer is choice (C). Just as only one configuration is normally seen at the α carbon, only one configuration is seen in the side chain chiral carbon.