A Distinguishing Test For Proteins

Perform a first-hand investigation and gather first-hand information about a distinguishing test for proteins

Biuret test

  • Known test for the identification of peptides and proteins
  • Involves the use of Biuret reagent which is made up of Sodium hydroxide and Copper (II) sulfate

Experiment: Protein Identification using Biuret Test

Reagent: Biuret reagent (1%  CuSO4  and 10% NaOH)


  1. Place two test tubes in a test tube rack. Transfer 2 mL water in the first and 2 – mL gelatin solution in the second tube.
  2. Add drops of Biuret reagent in each tube.
  3. Compare test tube 1 (Control) with the colour of the gelatine solution in test tube 2. Record for observations


  • The gelatine solution turned changes color to purple, indicating the presence of proteins or peptides


  • The change in colour is due to a coordination complex between the Cu2+ ions and the C—N and C=O atoms on the peptide group