What kind of peptide is alanylglycylphenylalanine?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Tripeptide
A peptide is named from its amino acids in order: each amino acid joined through its –COOH group takes the ending “-yl”, and the last one keeps its own name (as in glycylalanine, a dipeptide).
alanyl — alanine, amino acid 1.
glycyl — glycine, amino acid 2.
phenylalanine — amino acid 3, the end of the chain.
Three amino acids joined by two peptide linkages make a tripeptide.
NCERT (2026-27 edition):
10.2.3 Structure of Proteins – “If a third amino acid combines to a dipeptide, the product is called a tripeptide. A tripeptide contains three amino acids linked by two peptide linkages.”