MCAT Biochemistry Question 164: Answer and Explanation
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Question: 164
14. Which of the following amino acids will provide the most energy when degraded?
- A. Glycine
- B. Alanine
- C. Valine
- D. Isoleucine
Correct Answer: D
Explanation:
The energy contribution of an amino acid depends on its ability to be turned into glucose through gluconeogenesis (glucogenic amino acids), ketone bodies (ketogenic amino acids), or both. All of the amino acids listed in the answer choices are glucogenic; isoleucine is also ketogenic. The energy acquired from an amino acid will also depend on the number of carbons it can donate to these energy-creating processes, which depends on the size of its side chain. Isoleucine has the largest side chain of the answer choices, and will thus contribute the most energy per molecule.