When two molecule of –amino acids similar or different combine in this way that the amino group of one molecule with carboxy group of the other molecule, this result in the elimination of water molecule and the formation of new bond-CO NH- . This type of bond is called peptide bond or peptide linkage. The product of reaction is called dipeptide. For example, COOH group of valine combine with NH₂ group of alanine, we get dipeptide Valylalanine (Val-Ala) as final product, as shown below:-