Biochemical tests

• What are the two classifications of sugars based on their reducing properties?

  Reducing sugars and non-reducing sugars
• Which types of sugars are classified as reducing sugars?

  All monosaccharides and some disaccharides (maltose and lactose)
• What is the procedure for conducting the Benedict's Test for reducing sugars?

  1. Add equal volumes of test solution and Benedict's solution to a test tube.
  2. Heat the mixture in a gently boiling water bath for about 5 minutes.
  3. Observe colour change to determine the concentration of reducing sugar.weigh the precipitate formed.
• What indicates a positive result in the Benedict's Test?

  A coloured precipitate forms
• What is the procedure for testing non-reducing sugars using the Benedict's Test?

  1. Add dilute hydrochloric acid to the test solution and heat it.
  2. Neutralize with sodium hydrogencarbonate.
  3. Carry out the Benedict's test as for reducing sugars.
• What does a blue solution indicate after testing for non-reducing sugars?

  It means there is no sugar present (either reducing or non-reducing)
• How can glucose be tested for using test strips?

  By dipping the strips in a test solution and observing the color change
• What does a color change in glucose test strips indicate?

  It indicates the presence of glucose
• What is the procedure for the Iodine Test for starch?

  1. Add iodine dissolved in potassium iodide solution to the test sample.
  2. Observe the color change:

  • From browny-orange to dark blue-black if starch is present.
  • Stays browny-orange if no starch is present.
• What indicates the presence of protein in the Biuret Test?

  The solution turns purple
• What are the steps in the Biuret Test for proteins?

  1. Add a few drops of sodium hydroxide solution to make the test solution alkaline.
  2. Add some copper(II) sulfate solution.
  3. Observe the color change to determine protein presence.
• What is the procedure for the Emulsion Test for lipids?

  1. Shake the test substance with ethanol for about a minute.
  2. Pour the solution into water.
  3. Observe the color change:

  • Turns milky if lipid is present.
  • Stays clear if no lipid is present.