Biological Molecules

• Carbohydrates: made from Carbon, Hydrogen and Oxygen (CHO)
• Fats and oils: made from Carbon, Hydrogen and Oxygen (CHO)
• Proteins: made from Carbon, Hydrogen, Oxygen, Nitrogen and sometimes Sulfur (CHON{S})
• Basic units (monomers) --> Large molecules (macromolecules):

  • Simple sugars --> Starch and glycogen
  • Fatty acids and glycerol --> Fats and oils
  • Amino acids --> Proteins

  
• Test for Starch: Add few drops of iodine, +ve result = blue / black colour
• Test for Reducing sugars: Add Benedict’s reagent, then mixture is heated in water bath for 2 to 3 minutes. +ve result = brick red precipitate, -ve result = remains blue
• Test for Proteins: Add few drops of Biuret reagent, +ve result = mauve colour
• Test for Fats: Emulsion test; ethanol is added to mixture, and this is poured into a test tube with an equal amount of distilled water, +ve result = milky-white emulsion
• Test for Vitamin C: Decolourisation of DCPIP shows that a vitamin C is probably present.
• Chromosomes are made of a molecule called DNA
• Each chromosome is a very long molecule of tightly coiled DNA
• Two strands of DNA coiled together to form a double helix
• Each strand of DNA contains chemicals called bases
• Cross-links between DNA strands are formed by pairs of bases
• The bases always pair up in the same way:

  • A and T
  • C and G