BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Lead sulfide test (or Lead acetate test) is a biochemical test for the detection of amino acids like cysteine and cystine. The test is a specific test for the detection of amino acids containing sulfur, S-S group in cysteine, and S-H group in cystine.

Detailed explanation-2: -Lightly spray or place a drop of hydrogen peroxide (3% v/v ) on the test paper. Record any colour change. The test is positive for sulfur if the paper turns dark brown or black after exposure to the fumes from the sample and then turns white after exposure to hydrogen peroxide.

Detailed explanation-3: -A test to detect hydrogen sulfide in a fluid by discoloration of a paper moistened with the lead acetate solution. It is important to determine the presence and amount of hydrogen sulfide because this gas is extremely poisonous, highly flammable, explosive and corrosive.

Detailed explanation-4: -Lead sulfide test is used for the identification of protein amino acids cysteine and cystine which contains sulfur group in their side chain from a sample. The sulfur-containing methionine also gives negative results. This test is used to test cystine in the urine of kidney patients.