Testing for Biological Molecules

• What is the test for reducing sugars?

  Benedicts
• Give an example of a reducing sugar

  Glucose
• What colour is benedicts reagent?

  Blue
• After you add benedicts reagent, what do you do?

  Heat in a water bath
• What temperature is the water bath set to?

  75 degrees C
• What is formed to show a positive result?

  Coloured precipitate
• THe higher the concentration of reducing sugarst the closer to __________ the solution will be

  Brick red
• For non reducing sugars, what do you have to add to the solution before carrying out benedicts test as normal?

  Dilute HCl, heat (using water bath at 75C) the add sodium hydrogen-carbonate
• What element is used to test for starch?

  Iodine
• State the colour change for if starch is present

  Brown/orange to blue/black
• What test is used to test for proteins?

  Biuret's test
• WHat do you add first (biuret test)

  Sodium Hydroxide
• Why do you add sodium Hydroxide first?

  To make solution alkaline
• What is added second?

  Copper (II) sulfate
• What colour is copper (II) sulfate?

  Blue
• State the colour chnge seen if proteins are present?

  Blue to purple
• Wha tis the test for lipids?

  Emulsion test
• What is added to substance first?

  Ethanol
• WHat do you do with substance to get it to dissolve in the ethanol?

  Shake for approx 1 min until fully dissolved
• What do you do next with your solution?

  Pour solution into water
• What is seen if lipids are present?

  Milky emulsion