Biological molecules

• Biological molecules are molecules found in living organisms. They’re generally long, complex molecules made up of smaller basic units.

  • Carbohydrates
  • Protiens
  • Lipids
• Biological molecules can be broken down to fuel respiration.
• Carbohydrates - are made up of carbon, hydrogen and oxygen.

  The smallest units, monomers, are simple sugars - such as glucose or fructose molecules - that are joined together into long chains, polymer, to make large, complex carbohydrates.
• Proteins - are made up of Amino acids.

  They are polymers that are made up of long chains of monomers.

  Amino acids all contain carbon, nitrogen, hydrogen and oxygen atoms.
• Lipids - are made up of fatty acids and Glycerol.

  Unlike carbohydrates and proteins they are not polymers because they don’t form a long chain of repeating unit.

  Lipids contain carbon, hydrogen and oxygen atoms.
• Sugars are tested for using Benedict’s Reagent.

  Starch is tested for with Iodine.

  Lipids are tested for with the Emulsion Test.

  Proteins are tested for using the Biuret Test.
• Benedict’s Reagent -

  Reducing Sugars - included simple sugars made from just one unit e.g. glucose.

  Add (blue) Benedict's Reagent to a sample and heat in a water bath. If test is positive it will form a coloured precipitate.

  Non-Reducing Sugars - e.g sucrose

  Add dilute hydrochloride acid and heat in water bath. Add sodium hydrogen carbonate then carry out the Benedict’s test.
• Iodine test

  Just add Iodine solution to the test sample

  • If starch is present the colour changes from browny orange to blue back
  • If no starch the colour stays the same
• Emulsion Test

  Shake the test substance with Ethanol for about a minute until it dissolves then pour the solution into water.

  • If lipids then they will show up as a white milky emulsion.
• Biuret Test

  Add a few drops of sodium hydroxide to make the solution alkaline then add some copper(II) sulfate solution.

  • If no protein the solution will stay blue.
  • If protein is present the solution will turn purple.