Amino Acids
Amino acids are colourless, crystalline, water soluble and animated organic acids formed of C, H, O, N and in some S. Each amino acids has at least one carboxylic group (– COOH) and one amino group (– NH2) attached to α-carbon, hence α-amino acids. The α-carbon also bears one hydrogen and a hydrocarbon which in case of glycine (simplest and smallest) is a second hydrogen.
Amino acids can also be refereed as substituted methanes. There are some 200 amino acids, out of which 20 occur in proteins. Proline and hydroxyproline have – NH (imino group) instead of – NH2. They are,therefore, imino acids instead of amino acids.
A particular property of amino acids is the ionizable nature of NH2 and COOH groups. These fully ionized species known as Zwitter ions have both a positive and a negative charge.
At isoelectric point, amino acid is present in form of zwitter ion
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