lipids

• lipids are triglycerides formed by the combination of one glycerol molecule and three fatty acid molecules joined together by condensation reaction where three molecules of water are removed and ester bonds are formed between the fatty acid and glycerol molecules
• lipids, like carbohydrates contain carbon hydrogen and oxygen but in proportion to the carbon and hydrogen they contain much less oxygen
• lipids are non polar compounds and are insoluble in water
• phospholipids - hydrophilic head and hydrophobic tail
• waxes are lipids that melt above 45 degrees - they waterproof the exoskeleton of an insect and the cuticle of a leaf
• saturated lipid - a lipid that contains only single bonds between carbon atoms
• unsaturated lipid - a lipid with one or more double bonds between carbon atoms
• roles of lipids -

  1. phospholipids - biological membranes
  2. triglycerides - energy reserve, thermal insulation, protection for internal organs, metabolic water (water released in chemical reactions)
  3. waxes - reduce water loss
• testing for fats and oils -

  sample is mixed with ethanol which is then mixed with equal volume of water - because fats are insoluble in water they form an emulsion and the mix becomes cloudy