Peptide Bonds

A peptide bond (amide bond) is a covalent chemical bond formed between two amino acid molecules. Amino acids are connected by a dehydration reaction, marked by the removal of water. The resulting covalent bond is called a peptide bond. A polypeptide, regardless of length, has a single amino acid end (N-terminus) and a single carboxyl end (C-terminus).

At the top are two amino acids beside each other. Each amino acid has an amino group consisting of one nitrogen bound to 3 hydrogens. The nitrogen is bound to a central carbon which is bound to an R group. The central carbon is also bound to a carboxyl group. The oxygen atom from the left amino acid is highlighted in green along with two hydrogens attached to the nitrogen of the second amino acid. These result in water being released and the two molecules being merged together to create a peptide linkage. The peptide linkage is the bond between the carbon of the left carboxyl group and the nitrogen of the right amino acid. The left is the N terminus and the right side is the C terminus.

Figure 1: Amino acids are bound by peptide bonds to form polypeptides. The linkage occurs between the amino and carboxyl group releasing H20 in the process.