LIFE SCIENCE

Detailed explanation-1: -The tryptophan indole ring reacts with glyoxylic acid in the presence of sulphuric acid (VI) to form a product of a red-violet colour.

Detailed explanation-2: -The indole group of tryptophan reacts with glyoxylic acid (glacial acetic acid, which has been exposed to light, always contains glyoxylic acid CHOCOOH as an impurity) in the presence of concentrated H2SO4 to give a purple color. Apply this test to glycine, tryptophan and tyrosine.

Detailed explanation-3: -A purple ring appears between the two layers if the test is positive for tryptophan. Tryptophane due to its indole ring condenses with the aldehyde glyoxylic acid (OCH-CO2H) in presence of concentrated H2SO4 to produce a purple ring.

Detailed explanation-4: -The Hopkins-Cole reaction, also known as the glyoxylic acid reaction, is a chemical test used for detecting the presence of tryptophan in proteins. A protein solution is mixed with Hopkins Cole reagent, which consists of glyoxylic acid. Concentrated sulfuric acid is slowly added to form two layers.

Detailed explanation-5: -Interpretation The tryptophan indole ring reacts with glyoxylic acid in the presence of H2SO4 to form a product of a purple/violet colour. Glyoxylic acid is a polluting component of concentrated acetic acid. If a purple/violet ring appears between the two layers it confirms the presence of tryptophan in protein.