Amino Acid
An organic molecule that serves as the building block of peptides and proteins. There are 20 standard amino acids encoded by human DNA, each with a unique side chain that determines its chemical properties and role in biological processes.
Technical Context
Amino acids are linked together by peptide bonds to form chains. The sequence of amino acids determines the three-dimensional structure and function of the resulting peptide or protein. Each amino acid has an amino group (-NH2), a carboxyl group (-COOH), and a variable side chain (R group). The 20 standard amino acids are classified by their side chain properties: hydrophobic (e.g. leucine, valine), hydrophilic (e.g. serine, threonine), positively charged (e.g. lysine, arginine), and negatively charged (e.g. aspartate, glutamate). Non-standard amino acids, including D-amino acids and non-natural residues, are frequently incorporated into synthetic peptides to improve stability against enzymatic degradation.