Lipids

• lipids are macromolecules, not polymers
• insoluble in water
• uses - long term energy store, thermal insulation, membranes, insulating nerve axons (myelin sheath), protecting organs, hormones and buoyancy
• in the digestive system, lipids are broken down by lipase into glycerol and fatty acids
• glycerol - 3 carbon molecule with an -OH (hydroxyl) group bonded to each carbon
• fatty acid - a carboxyl group attached to a variable hydrocarbon tail
• saturated - no double bond between carbons in hydrocarbon chain
• monounsaturated - one C=C
• polyunsaturated - many C=C
• double bonds are easier to break down and digest than single bonds
• fats contain saturated fatty acids
• oils contain unsaturated fatty acids
• an ester bond is formed by a condensation reaction between each of the three OH groups on the glycerol and the OH group of each fatty acid
• hydrocarbon tails are hydrophobic - repel water - insoluble - non polar
• glycerol is hydrophilic
• phospholipid - cell membrane 'bilayer'

  phosphate group is hydrophilic - polar

  
• add ethanol to test substance

  shake for one minute

  add to water

  milky/cloudy emulsion indicates a lipid