ABSTRACT
Amino acids play a double role on living cells as building blocks of proteins and as intermediates in metabolism. Amino acids are organic compounds which contain both an amino group (pK by 9) and a carboxyl group (pK by 2) bound to a speci‚c side chain which confers characteristic properties to each amino acid. The precise amino acid content, and the sequence of amino acids, of a speci‚c protein, determines the biological activity of that protein. In addition, proteins contain within their amino acid sequences the necessary information to determine how that protein will fold into a three-dimensional structure, and the stability of the resulting structure. As a result, the characteristics of even a small, relatively simple, protein are a composite of the properties of the amino acids which comprise the protein. That is why each amino acid within a protein is unique and irreplaceable.
