Question

a student heats a test tube containing a large amount of protein and Biuret reagent. She notices a colour change from violet to blue. Explain why heating causes this colour change?

Answer 1

Proteins are polypeptides that are composed of amino acids -- each amino acid is connected by a peptide bond.

Biuret's solution changes color (from blue to purple) in the presence of peptide bonds. A reverse reaction would indicate a lose of peptide bonds. Thus, the protein is being denatured.