Question

which color change represents a positive reaction for the presence of protein using the biuret test? multiple choice color change from green to red color change from purple to blue color change from blue to purple color change from yellow to green

Explanation:

The Biuret test is used to detect proteins. In the presence of proteins, the copper - sulfate in the Biuret reagent reacts with peptide bonds. The initial blue color of the reagent (due to copper ions in an alkaline solution) changes to purple when proteins are present.

Answer:

color change from blue to purple