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 uses a copper - sulfate solution which is blue. In the presence of protein, the copper ions in the Biuret reagent react with peptide bonds, resulting in a color change to purple.

Answer:

color change from blue to purple