Define Peptide bond

A peptide bond is a type of covalent bond that forms between the carboxyl group (–COOH) of one amino acid and the amino group (–NH2) of another amino acid during protein synthesis. This bond is formed through a condensation reaction, also known as a dehydration synthesis, where a molecule of water is released as a byproduct. The resulting linkage between the two amino acids is called a peptide bond, and the chain of amino acids formed by successive peptide bonds is known as a polypeptide chain.

The peptide bond is formed when the carbonyl carbon of one amino acid undergoes nucleophilic attack by the amino group of another amino acid. As a result, the carbonyl oxygen becomes doubly bonded to the nitrogen of the amino group, while the carbon atom becomes bonded to both the amino group and a hydrogen atom. This arrangement results in a planar structure with partial double bond character, restricting rotation around the C-N bond and giving the peptide bond its characteristic rigidity.

Peptide bonds play a fundamental role in the structure and function of proteins, as they link amino acid residues together to form the primary structure of a protein. The sequence of amino acids in a protein chain, dictated by the order of peptide bonds, determines the protein's overall structure and function. Additionally, peptide bonds contribute to the stability and conformational flexibility of protein structures, influencing their biological activity and interactions with other molecules.