Aspartic acid. Molecular model of the amino acid aspartic acid (C4.H7.N.O4). Structurally an alpha amino acid, aspartic acid is a non-essential amino acid. It can be synthesised by the body and so does not need to come from the diet. Also known as aspartate (the conjugate base of aspartic acid), this amino acid is a precursor to several other amino acids including methionine, threonine, isoleucine and lysine. Atoms are represented as spheres and are colour-coded: carbon (grey), hydrogen (white), nitrogen (blue) and oxygen (red).