3. Qualitative tests of functional groups in lipids.

 3.      Qualitative tests of functional groups in lipids.

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2. Qualitative Test for functional groups in proteins.

 2.      Qualitative Test for functional groups in proteins.

Qualitative tests of functional groups in Protein

 Qualitative tests of functional groups in Protein 

Aim:-   Detection of  Protein 

Preparation of Sample solution for protein test. 

For experiments fresh 5% solution of egg white is prepared. Egg white is filtered through cotton. Dissolve 5ml  of egg white into 95 ml of distilled water for 5% egg white solution. Proteins show both precipitation and colour reactions. 

Preliminary test for identification of unknown substance from the sample

Sr. No.	Test	Observation	Inference
1	Preliminary Test	coagulation	Protein  may be present carbohydrates may be present
		No coagulation	carbohydrates may be present
2	Biurate test Take 3 ml  of 5% O.S. in a test tube, add 1 ml of 40% NaOH solution to make it strongly alkaline, and then add 2 drops of 1 % copper sulphate solution.	Violet or pink colour appears.	Protein may be present.
3		No violet or pink colour	Carbohydrates may be present.

 

 Qualitative tests of functional groups in Protein 

Test for Protein

Proteins, found in animals and plants are important building blocks formed by amino acids, condensed together by a peptide linkage. They contain free amino and carboxyl groups and so they can combine with bases and acids depending upon the pH of the medium. On hydrolysis, proteins break into peptones, proteoses, peptides and amino acids. Chemical behaviour of the proteins is due to the amino acids in the protein molecules.

           

Sr. No.	Test	Observation	Inference
1	Mercuric chloride test. In a test tube take 3 ml  of 5% O.S. then add mercuric chloride drop by drop.	White turbidity is produced first which becomes thick and granular.	Protein is present
2	Precipitation of proteins with heavy metals  O.S+Hgcl2 drop by drop + lead acetate	White ppt.	Protein present
3	Hellers' test. (Ring test) Take 3 ml of concentrated HN03 in a test tube and then add very carefully 3 ml of 5% egg white solution by means of a pipette in such a manner that it forms upper layer.  Mix gradually by rotating between palms.	A white ring is formed at the junction of the two solutions.	Protein is present
4	Ninhydrin test. Take 1 ml  of 5% O.S.  and add 4 drops of 0.1 % ninhydrin solution and boil for one minute. Cool the test tube.	Blue colour develops.	Protein present
5	Xantho protein Recn  O.S. + 1ml HNO3(conc.) & then boil	White ppt turns Yellow after boiling	Protein confirmed
6	Million test:- O.S.. +2ml HgSo4 boil cocl+ few drops of NaNO2 then heat	Yellow to dark red ppt	Protein confirmed

 

Result: The given sample contains protein.

Qualitative tests of functional groups Protein/ Carbohydrate and Lipids.

 Qualitative tests of functional groups Protein/ Carbohydrate and Lipids.   

Use this link for the procedure

1.      Qualitative test for functional groups in carbohydrates.+

Qualitative tests of functional groups in carbohydrates

                                Qualitative tests of functional groups in Carbohydrate 

Carbohydrates are abundantly found in the plants and as glycogen in the animals. In animals they are found in free stored state as glycogen or in combination with proteins as glycoprotein. The name carbohydrate is given because they are composed of carbon, hydrogen and oxygen atoms.

Many carbohydrates are of low molecular weight and having sweet taste. Carbohydrates are classified into 3 groups : (1) Monosaccharides or simple sugars (C6H1206), (2) Di- and tri-saccharides or compound sugars, (3) Polysaccharides.

For experiment make 2% solutions of the Dextrose-D or Fructose and perform the following experiments in order to identify the reducing action of glucose and fructose

Sr. No.	Test	Observation	Inference
1	Reduction test. In a test tube take 3 ml  of distilled water, then add a drop of methylene blue (1%). The water becomes blue coloured. Add 0.5 cc of 40% NaOH. Boil the solution. Colour is not discharged, blue colour remains. Add 1 ml  of 0.2% OS and boil.	Decoloration	Carbohydrate may be present.
2	Fehling's test. Procedure: Take 5ml  of Fehling's solution and boil. Add 1 ml  of OS  and boil again.	Yellow or brick-red precipitate	Glucose is  present.
3	Benedict's test. In a test tube 5 ml  of Benedict's reagent, then add 0.5 ml  of glucose solution and heat to boiling. Boil for 2 minutes. Cool the solution under tap water.	Green, yellow or red precipitate
4	Picric acid test. In a test tube take 3 ml  of 2% O.S. then add 1 ml  of picric acid saturated solution and then add 1 ml  of 40% NaOH.	Formation of  red colour.	Glucose is present
5	Rapid furfural test. Take 1 ml of 2% fructose solution, add 6 drops at a-naphthol, then add 5 ml of conc. HCI in a test tube and boil.	Deep purple colour appears.	Fructose is present

 

Result: The given  sample contains  Glucose / Fructose