<prompt> Ninhydrin test is used for ?Bile saltsAmino acidsNucleic acidLipids  <response>: Ans. is b i.e., Amino acids Impoant chemical reactions of amino acids Following are some impoant chemical reactions. A. Reaction used to determine amino acid sequence in polypeptide chain : - Generally, amino terminal N-terminal of amino acid is tagged with some reagent. It is split off by hydrolysis and tagged amino acid is identified. The reaction is, then, repeated with new N-terminal of subsequent amino acid and so on. The two reactions are used for identification of amino acid sequence : ? Sangers reaction : - Uses Sangers reagent 1 -fluoro-2,4-dinitrobenzene to tag amino terminal. Edmans reaction : - Uses Edmans reagent phenylisothiocyanate to tag amino terminal. B. Reaction used to identification of individual or group of amino acids : - These reactions are frequently used for qualitative detection and quantitative measurement of various amino acids. Ninhydrin tese : - All a-amino acids. Xanthophoretic reaction : - Aromatic amino acidse Tyrosine, tryptophan, phenylalanine. Millans teste Millon-Nasse reaction : - Tyrosinedeg phenol group of tyrosine. Therefore millons test is positive in tyrosinosisdeg. Aldehyde test : - Tryptophan indole ring Hopkins-tole reaction : - Tryptophan indole ring Sakaguchs reaction : - Arginine guanidinium group of arginine. Sulphur test : - Cysteine sulphydryl group Nitroprusside test : - Cysteine sulphydryl group Paulys test : - Histidine imidazole group Biuret reaction : - Peptide bond Diazo reaction Q Paulis : - Histidine or tyrosine. 