The biuret test for proteins gives
Correct answer: A. a violet colour with copper two ions in alkaline solution
- A. a violet colour with copper two ions in alkaline solution
- B. a brick red precipitate
- C. a silver mirror
- D. a blue black colour
Explanation
Copper two ions form a violet complex with the peptide linkages, so the test detects the presence of peptide bonds rather than any particular amino acid and requires at least two of them. A blue black colour with iodine is the test for starch and a brick red precipitate with Fehling's solution indicates a reducing sugar. The ninhydrin test is the alternative for free amino acids.
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About Importance of Proteins
Proteins are polymers of amino acids joined by peptide bonds, and their biological roles depend on primary, secondary, tertiary and quaternary structure. Coverage includes enzymes, hormones, antibodies, transport proteins, muscle fibres and structural tissues, together with denaturation and the effects of heat, pH and chemicals.
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