Which of the following amino acids would not create an aldehyde as a by-product?

• A. Cysteine
• B. Valine
• C. Proline
• D. Histidine
• E. Glycine

Answer: (C)

Verified step by step guidance

1. Understand the question: We need to identify which amino acid does not produce an aldehyde as a by-product. This typically involves understanding the structure and possible reactions of each amino acid.
2. Examine the structures: Look at the chemical structures of the amino acids provided in the image. Each amino acid has a unique side chain that can influence its chemical behavior.
3. Consider the reaction: Amino acids can undergo oxidative deamination, where the amino group is removed and converted into an aldehyde. This is more likely to occur in amino acids with side chains that can easily form aldehydes.
4. Analyze Proline: Proline is unique because it has a secondary amine in a cyclic structure, which makes it less likely to undergo oxidative deamination to form an aldehyde compared to other amino acids with primary amines.
5. Conclude: Based on the structure and the typical reactions, Proline is the amino acid that would not create an aldehyde as a by-product due to its cyclic structure and secondary amine.