Testing for Biological Molecules

• What is the purpose of testing for biological molecules in food samples?

  To determine the types of biological molecules present in the sample.
• What is Benedict's reagent used for?

  It is used to test for the presence of reducing sugars.
• What are reducing sugars?

  Reducing sugars are simple sugars made from one or two monosaccharide units.
• What happens when Benedict's solution is added to a sample containing reducing sugars?

  A coloured precipitate forms, indicating the presence of reducing sugars.
• How can you estimate the amount of reducing sugar in a solution using Benedict's test?

  By observing the speed of the color change in the solution.
• What should you do if your sample contains non-reducing sugars like sucrose?

  Add dilute hydrochloric acid and heat the sample before performing the Benedict's test.
• What indicates a positive result for non-reducing sugars in the Benedict's test?

  The solution changes color from blue to a different color.
• What does it mean if the solution stays blue after the Benedict's test?

  It means that there are no sugars present in the sample.
• How is starch tested for in a sample?

  By adding iodine solution to the test sample.
• What color change indicates the presence of starch when using iodine solution?

  The sample changes from browny-orange to dark blue-black.
• What is the emulsion test used for?

  To test for the presence of lipids in a sample.
• What is the procedure for the emulsion test for lipids?

  Shake the sample with ethanol, then pour it into water.
• What does a milky emulsion indicate in the emulsion test?

  It indicates the presence of lipids in the sample.
• What is the Biuret test used for?

  To test for the presence of proteins in a sample.
• What is the first step in the Biuret test?

  Add a few drops of sodium hydroxide solution to make the solution alkaline.
• What color change indicates the presence of protein in the Biuret test?

  The solution turns purple if protein is present.
• What does it mean if the Biuret test solution stays blue?

  It means that there is no protein present in the sample.
• What is the Anger Test mentioned in the material?

  It is a humorous reference to testing for anger by observing a red face.
• What conclusion can be drawn if a solution treated with sodium hydroxide and copper(II) sulfate turns purple?

  It indicates that the solution contains protein.