Would you expect any of the side chains in a typical peptide to undergo hydrolysis under physiological conditions?

• A. All amino acid side chains are hydrolyzed before peptide bond formation.
• B. No, side chains generally do not undergo hydrolysis under physiological conditions.
• C. Yes, all side chains are readily hydrolyzed under physiological conditions.
• D. Only the peptide bonds in the backbone undergo hydrolysis, not the side chains.

Answer: (B)

Verified step by step guidance

1. Understand the concept of hydrolysis: Hydrolysis is a chemical reaction where water is used to break bonds. In the context of peptides, hydrolysis typically refers to the cleavage of peptide bonds in the backbone, not the side chains.
2. Review the structure of amino acids: Amino acids have a backbone consisting of an amine group (-NH2), a carboxyl group (-COOH), and a unique side chain (R group). The peptide bond forms between the amine group of one amino acid and the carboxyl group of another.
3. Consider physiological conditions: Physiological conditions refer to the environment within living organisms, typically characterized by neutral pH (~7.4), moderate temperature (~37°C), and the presence of enzymes. Under these conditions, peptide bonds can be hydrolyzed by specific enzymes (e.g., proteases), but side chains are generally stable.
4. Evaluate the chemical properties of side chains: Amino acid side chains vary in structure and reactivity. While some side chains may participate in chemical reactions (e.g., phosphorylation, oxidation), hydrolysis of side chains is not a common occurrence under physiological conditions.
5. Conclude based on the information: The correct answer is that only peptide bonds in the backbone undergo hydrolysis under physiological conditions, not the side chains. This is because side chains are generally stable and do not readily undergo hydrolysis in this environment.