The bond is formed by a reaction. A peptide bond is an amide bond between two adjacent amino acids. The bond is formed between the carboxyl group of one amino acid and the amino group of a second amino acid with the elimination of water. The result is a linear chain with an N-terminus and a C-terminus. The chain can be extended into a polymer with additional amino acids. The polymer formed is called a polypeptide or a protein, depending on the number of amino acids joined. The amide bond can be broken by the addition of water across it in a hydrolysis reaction.