Which statements about peptide bonds are true

Which statements about peptide bonds are true?

A The formation of a peptide bond involves a dehydration reaction.

B A tripeptide contains three amino acid residues.

C Peptide bonds are ester linkages.

D A tetrapeptide contains five amino acid residues.

E Peptides are polymers of proteins.

The correct answer and explanation is :

Correct Answers:

✅ A The formation of a peptide bond involves a dehydration reaction.
✅ B A tripeptide contains three amino acid residues.

Explanation:

1. (A) The formation of a peptide bond involves a dehydration reaction – TRUE
   Peptide bonds are formed through a condensation (dehydration) reaction, where a water molecule (H₂O) is removed as the carboxyl (-COOH) group of one amino acid reacts with the amino (-NH₂) group of another. This reaction results in the formation of a covalent amide bond, linking amino acids together in a peptide chain.
2. (B) A tripeptide contains three amino acid residues – TRUE
   A tripeptide is a short peptide consisting of three amino acids connected by two peptide bonds. Each amino acid in a peptide is referred to as a residue after it has joined the chain.
3. (C) Peptide bonds are ester linkages – FALSE
   Peptide bonds are amide bonds, not ester linkages. Amide bonds are formed between the carboxyl (-COOH) and amino (-NH₂) groups of amino acids, whereas ester bonds occur between carboxyl and hydroxyl (-OH) groups (as seen in lipids and some other biological molecules).
4. (D) A tetrapeptide contains five amino acid residues – FALSE
   A tetrapeptide consists of four amino acid residues, not five. The number of amino acids in a peptide corresponds directly to the name prefix (e.g., tripeptide = 3, tetrapeptide = 4, pentapeptide = 5).
5. (E) Peptides are polymers of proteins – FALSE
   Proteins are polymers of peptides, not the other way around. Peptides are short chains of amino acids, while proteins are large, functional macromolecules composed of one or more long polypeptide chains.

Conclusion:

The correct statements are A and B, as they accurately describe peptide bond formation and peptide structure.