Biomolecules in the Cell > Proteins - Peptide Bond

• Bond formed between –COOH of one amino acid and –NH₂ of another by the elimination of water

\[ \begin{array}{c} \mathrm{H}_2\mathrm{N} - \mathrm{CH}_2 - \mathrm{COOH} + \mathrm{H}_2\mathrm{N} - \underset{\underset{\displaystyle \mathrm{CH}_3}{|}}{\mathrm{CH}} - \mathrm{COOH} \\ \downarrow \\ \mathrm{H}_2\mathrm{N} - \mathrm{CH}_2 - \boxed{\mathrm{CO}-\mathrm{NH}} - \underset{\underset{\displaystyle \mathrm{CH}_3}{|}}{\mathrm{CH}} - \mathrm{COOH} \\ \uparrow \\[-1ex] \text{Peptide linkage} \end{array} \]

• Dipeptide = 2 amino acids, 1 peptide bond
• Tripeptide = 3 amino acids, 2 peptide bonds
• Polypeptide = more than 10 amino acids
• Polypeptide chain has –NH₂ terminus (N-terminal) and –COOH terminus (C-terminal)