Amino acids are the building blocks of all biological proteins. Amino acids link together via peptide bonds in a particular order as defined by genes. Genes are translated by RNA to amino acid chains; the length and order of the amino acid chain then dictates the three-dimensional structure of a polypeptide or protein. While plants and bacteria can generally synthesize all 22 amino acids, mammals can naturally synthesize only ten of these; the others are dietary essentials.