5 cm3 dilute sodium hydroxide solution and 5 cm3 one percent copper sulphate solution are added to a solution of food specimen. The purple colour which is o...

Assessment: JAMB UTME - Biology - 1992 Subject: Biology

Question 1 Report

5 cm3 dilute sodium hydroxide solution and 5 cm3 one percent copper sulphate solution are added to a solution of food specimen. The purple colour which is observed shows the presence of
Answer Details
The purple colour observed after adding 5 cm3 dilute sodium hydroxide solution and 5 cm3 one percent copper sulphate solution to a solution of food specimen shows the presence of protein. This is because the Biuret test is used to detect proteins in a sample. In this test, the copper ions in the copper sulphate solution react with the peptide bonds in the protein molecule to form a purple complex. The intensity of the purple colour is directly proportional to the concentration of the protein present in the sample.

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