Question

Which of the following is an imino acid?

• A. Serine
• B. Alanine
• C. Glycine
• D. Proline

Answer 1

The Correct Option is D

Amino acids are primarily classified based on their chemical properties, functional groups, and how they interact in various biological processes. While most amino acids contain a primary amino group (-NH2), some, like amino acids, have a secondary amine group (-NH) as a distinctive feature.

Step 1: Identifying Imino Acids - Imino acids are unique in that their amine group forms part of a cyclic structure, unlike the common linear form found in most amino acids. - Proline is the only naturally occurring imino acid, with its amino group integrated into a pyrrolidine ring, a distinctive cyclic structure. 

Step 2: Analyzing the Options - Option (A) - Incorrect: Serine is a hydroxy amino acid, meaning it contains a hydroxyl group (-OH) rather than an imino group. - Option (B) - Incorrect: Alanine is a simple, aliphatic amino acid that does not exhibit any secondary amine group. - Option (C) - Incorrect: Glycine is the simplest amino acid, but it has a primary amine group and is not classified as an imino acid. - Option (D) - Correct: Proline stands out as the only imino acid, with a cyclic structure featuring a secondary amine group that sets it apart from others. 

Step 3: Conclusion Given that Proline is the only amino acid with a cyclic structure incorporating a secondary amine, it is the correct answer, making option (D) the right choice.