Peptide bond:A covalent chemical bond formed between two amino acids when the carboxyl group of one reacts with the amine group of another, releasing water.
C: terminal amino acid - The last amino acid in a peptide or protein chain, characterized by having a free carboxyl group (-COOH) that is not involved in a peptide bond.
Polypeptide:A linear organic polymer consisting of a large number of amino-acid residues bonded together in a chain, forming part of (or the whole of) a protein molecule