Question

How many of the given compounds will give a positive Biuret test ?
$\text{Glycine, Glycylalanine, Tripeptide, Biuret}$.

• A. 2.0
• B. 2.00
• C. 2.00
• D. 2
• E. 2.0
• F. 2

Answer 1

Answer: (A), (B), (C), (D), (E), (F)

Biuret test is a chemical test used to determine the presence of peptide bond in a substance.
Protein composes of many amino acids connected to each other through peptide bonds. Hence, Biuret test is used to determine the presence of protein in a sample.
In presence of an alkaline solution, blue-colored copper II ion can form a complex with the peptide bonds since the peptide has unshared electron pairs in nitrogen, and oxygen of water. Once this complex has been formed, the solution turns from blue to purple. The deeper the purple color, the higher is the number of peptide-copper complexes.




Dipeptides and free amino acids do not give biuret test. Hence glycine and glycylalanine do not give this test.