Amino Acid - Study Guide

Amino Acid Amino acids are compounds that have an amino group (-NH2) and a carboxylic acid (COOH) in the same molecule35 . Each amino acid is composed of a carbon atom that binds a hydrogen atom, an amino group, and a carboxylic group and one of the R groups which are different in the 20 amino acids and the structure of the R group determines the identity of the amino acid and its special properties36. The side chain (R group) depending on the functional group can be aliphatic, aromatic, acidic, basic, hydroxylic, sulfur-containing, or amidic37 . From the general structure of these amino acids, the α carbon atom is an asymmetric carbon atom, except when R is an H38 atom. . The molecular structure of 20 protein amino acids has standard groups, namely the amino group and the carboxyl group, while the R group varies. Because of the atom α carbon is an asymmetric carbon atom, except when R is an H atom so that each amino acid has the property of being able to rotate planes of polarized light or known as optical activity which can be described using the Fischer projection formula and with a ball and rod model so that it has 2 configurations, namely D and L39. An amino acid molecule is said to have an L configuration, if the –NH2 group is to the left of the α carbon atom. If the position of the –NH2 group is on the right, then the amino acid group has a D configuration. In nature, what is found in abundance is L- α -amino acid, while only a small amount of D-ÿ-amino acid is found. All twenty amino acids of the C α protein are asymmetric except glycine, which is an amino acid whose C α is symmetric. As stated in the previous discussion, if protein is hydrolyzed under control, a peptide or amino acid will be produced as a molecular unit. The hydrolysis results of all natural proteins still produce 20 amino acids40. Untill today there are 150 amino acids have been discovered contains the 20 amino acids that form proteins and the rest are free amino acids or in complex form with other compounds or in the form of a peptide which is called non-protein amino acids41 . Bradykinin or a peptide hormone is one example of an amino acid in peptide form. An example of an amino acid in complex form with other compounds is Sadenosylmethionine, and non-protein amino acids are also found in nucleic acid protein complexes, namely in ribosomes and histones. Based on the structure of amino acids, in general they have the same basic structure which differentiates one amino acid from another, namely the chain group a branch called the R group which determines the physical and chemical properties of a protein42 .