Question

1. What are the Detection Methods for Carbohydrates, Lipids, and Protein?

Answer 1

Answer:- Detection Method of Protein.

Protein are complex nitrogenous substances made up of a large number of amino acid molecules.

Test of proteins:-

1. Biuret test :- Take 2.0 to 3.0 of protein solution or egg albumin solution in a test tube , add an equal volume of 10%NaOH , mix thoroughly and add 0.5% CuSO4 solution drop- by - drop.

Result: Mix it well until a purple - violet or pinkish - violet colour or protein develops.

Million 's Test :- Take 5.0 ml of dilute solution of protein or egg albumin in a test tube , add 3 to 4 drops of Million's reagent .Mix and heat the mixture till it boils .

Result :- White precipitate of protein appears which gradually turns pink or red on warming.

Xanthoproteic Test :- In a test - tube take 3 ml of 5% egg white solution and add 1 ml of conc. HNO3 and boil. Cool the tube and add excess of 40%NaOH or ammonia to make alkaline.

Result :- Yellow colour appears that changes to orange, which indicate presence of protein.

Carbohydrates:-

The carbohydrates are the compounds of the carbon , hydrogen and oxygen . Chemically carbohydrates are polyhydroxy aldehydes or ketones.

Tests of carbohydrates:-

Fehling 's test :- Take 5.0 ml of Fehling 's solution in a test tube , add 1.0 ml of 0.2% sugar solution and boil.

Result :- The colour changes with the formation of yellow or brick red precipitate . It is reducing monosaccharide.

Benedict's test :- Take 5.0 ml of Benedict's reagent in a test tube , add 0.5 ml of sugar solution and mix it well . Heat to boil for two minutes then cool under tap water.

Result :- Green , yellow or red precipitate is formed. Test sample contains reducing monosaccharide.

Lipids :-

Test of lipids:-

Solubility test :- In a five test tubes (A, B,C,D,E) take 3 ml of water, alcohol ,ether, benzene and chloroform. To each test tube add 2 or 3 drops of lipid . Shake well and note the solubility.

Result:- The lipid floats on water but it is miscible with ether, benzene and chloroform, while it sinks to the bottom in alcohol.

Colour test with Sudan III:- In a test tube containing 0.5 ml of ether or chloroform, add 0.5 ml test sample drop by drop . When test sample is fully dissolved, add one drop of Sudan III reagent in the test tube.

Result :- Red colour appears showing presence of fat.