Test for proteins

• What is added to a liquid solution to make it alkaline?

  Sodium or potassium hydroxide
• What is the color of copper (II) sulfate solution?


  Blue
• What does Biuret reagent contain?

  An alkali and copper (II) sulfate
• What indicates the presence of protein in a sample during the Biuret test?

  Color change from blue to lilac/purple
• How can you enhance observation of the color change in the Biuret test?

  Hold test tubes against a white tile
• What does it mean if no color change is observed in the Biuret test?

  No protein is present
• How many peptide bonds must be present for the Biuret test to work?

  At least two peptide bonds
• What is the result of the Biuret test if the sample contains only amino acids or dipeptides?

  The result will be negative
• What type of test is the Biuret test?

  Qualitative
• What does the Biuret test not provide regarding protein in a sample?

  Quantitative value of protein amount