Question

Write a short note on peptide bond.

Answer 1

1. The amino acids are linked covalently by peptide bonds.
2. The carbonyl group of the first amino acid reacts with the amino group of the second amino acid to give an amide linkage (−CONH) between these amino acids. This amide linkage is called a peptide bond.
   \[\begin{array}{cc}
   \ce{\underset{(Glycine)}{H2N - CH2 - COOH} + H2N - CH - COOH ->[][-H2O] H2N - CH2 - C - N - CH - COOH}\\
   \phantom{....................}|\phantom{.................................}||\phantom{....}|\phantom{....}|\\
   \phantom{.........................}\ce{\underset{(Alanine)}{CH3}}\phantom{.........................}\ce{\underset{(Compound is Glycylalanine)}{\underset{(Peptide Bond)}{O\phantom{...} H\phantom{..} CH3}}}
   \end{array}\]
3. The resulting compound is called a dipeptide. Because two amino acids are involved in getting one peptide bond.
4. If a large number of amino acids are combined through a peptide bond, the resulting giant molecule is called a protein.
5. The amino end of the peptide is known as the N-terminal, while the carboxy end is called the C-terminal.