Classification of amino acids Amino acids are classified

Classification of amino acids • • Amino acids are classified according to Solubility Taste Reactions Aromatic and aliphatic amino acids Sulphur content Essential and non essential Glucogenic and ketogenic amino acids

CLASSIFICATION ACCORDING TO SOLUBILITY • Water soluble amino acids: glycine, alanine • Amino acids soluble in hot water: phenyl alanine • Amino acids soluble in alcohol: proline and hydroxy proline.

1 - Neutral amino acids: These amino acids contain one amino group and one carboxylic group. Both groups neutralize each other. Ex. Alanine, serine, cysteine glycine.

according to the reaction 2 - Acidic amino acids: These amino acids contain two acidic carboxylic groups and one basic amino grouup. Ex. Aspartic and glutamic acid. 3 - Basic amino acids: These amino acids contains two basic amino groups and one acidic carboxylic group. Ex. Lysine, arginine.

Classification of A. A according to aromatic and aliphatic A. A 1 - Aromatic amino acids: These A. A are characterized by the presence of benzene rings. Ex. Phenyl alanine, tyrosine and tryptophan.

2 - Aliphatic amino acids: These A. A are characterized by the absence of the aromatic ring. Ex. Alanine, serine, lycine. 3 - Heterocyclic amino acids: These amino acids are cyclicn in structure but not aromatic. Ex. Proline, hydroxyproline, histidine.

Classification of amino acids according to their sulphur content • 1 -sulphur containing amino acids: methionine, cystine and cysteine. They provide the body with sulphur. • 2 - Sulphur free amino acids: these are the rest of amino acids.

Classification of amino acids to essential and non essential A. A. • 1 - Essential amino acids: these are amino acids • • which should be taken in diet. The essential amino acids are 10: Phenyl alanine Tryptophan - Threonine Methionine Arginine - Leucine Isoleucine Lysine - Valine histidine

• 2 - Non essential amino acids: • These amino acids can be formed in the body by different ways: • Oxidation, (addition of oxygen). • Oxidation (removal of H 2). • Reduction • Transamination

General properties of amino acids All amino acids are optically active except glycine. All amino acids are present in crystalline state. Amino acids are soluble in cold water. The amino acids may be sweet in taste as glycine, serine or tasteless as leucine and tryptophan. • The alpha amino acids are characterized by their reaction with ninhydrine. This reaction depends on the presence of free NH 2 and free COOH groups. • •

• All amino acids give negative biuret test. • All amino acids are of low molecular weight as compared with proteins. • By condenstion of amino acids protein is reformed • Amino acids dipeptide tripeptide polypeptide peptone proteins.