BIOMOLECULES AND ENZYMES

Detailed explanation-1: -Proteins can be detected through the use of the Biuret test. Specifically, peptide bonds (C-N bonds) in proteins complex with Cu2+ in Biuret reagent and produce a violet color. A Cu2+ must complex with four to six peptide bonds to produce a color; therefore, free amino acids do not positively react.

Detailed explanation-2: -Why would amino acids give a negative result in the Biuret Test for Proteins? As 2 peptide bonds are required for the formation of the chelate complex, single amino acids-no peptide bonds present-and dipeptides-only 1 peptide bond present – give a negative result.

Detailed explanation-3: -The Colour turns purple. All proteins and peptides give positive results. Only amino acid, Histidine, gives a positive result.

Detailed explanation-4: -Biuret method Compounds containing peptide bonds give a characteristic purple colour when treated in alkaline solution with copper sulfate. This is termed the ‘biuret’ reaction because it is also given by the substance biuret NH2CONHCONH2.

Detailed explanation-5: -Answer and Explanation: Glycine and tyrosine will give negative test results because of the absence of peptide bonds, These are amino acids that make up proteins, however, single amino acids do not have peptide bonds. Gelatin, albumin, and casein are proteins made up of peptide bonds.