Proteins are polymers of amino acid monomers. There are twenty different amino acids that are used to build proteins in organisms. All amino acids have a carbon atom bonded to a hydrogen atom, an amino group (NH2), and a carboxyl group (COOH) the side group R is different on every amino acid.
Amino acids are linked by peptide bonds. These are covalent bonds formed between an amino group on one amino acid and the carboxyl group on another. Through these bonds amino acids are linked into chains called polypeptides. Proteins are made of one or more polypeptides.
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