Biological molecules

• Carbohydrates

  • Made of simple sugars
• Proteins

  • Made of amino acids
• Lipids

  • Made from glycerol and fatty acids
• Test for sugars using benedicts solution.

  • Colour turns from blue -> green -> yellow -> orange -> brick red
• Test for starch using iodine

  • Browny-orange -> blue-black
• Test for lipids using the emulsification test

  • Shake the test substance with ethanol until it dissolves, then pour into water
  • If any lipids present, they will show up as a milky emulsion
• Test for proteins using biuret solution

  • Add some sodium hydroxide solution to make the solution alkaline
  • Then add some copper (II) sulfate solution
  • If protein is present, the solution turns for blue -> purple