Which of the following lists contains all three branched-chain amino acids (BCAAs)?

• A. Alanine, Glycine, and Serine
• B. Leucine, Isoleucine, and Valine
• C. Lysine, Methionine, and Threonine
• D. Phenylalanine, Tyrosine, and Tryptophan

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the concept of branched-chain amino acids (BCAAs). BCAAs are essential amino acids characterized by their aliphatic side chains with a branch. The three BCAAs are Leucine, Isoleucine, and Valine.
2. Step 2: Review the options provided in the problem. Each option lists three amino acids, and you need to identify the set that includes all three BCAAs.
3. Step 3: Analyze the first option: Alanine, Glycine, and Serine. None of these amino acids have branched side chains, so this option does not contain any BCAAs.
4. Step 4: Analyze the second option: Leucine, Isoleucine, and Valine. All three amino acids in this set are BCAAs, as they have branched aliphatic side chains.
5. Step 5: Confirm that the other options (Lysine, Methionine, and Threonine; Phenylalanine, Tyrosine, and Tryptophan) do not include all three BCAAs. These amino acids have different structural features and functions, and none of these sets contain Leucine, Isoleucine, and Valine together.