1.5 Lipids

1.5 Lipids

TRIGLYCERIDES
1. Three (tri) Fatty Acids
2. Glycerol (glyceride)
3. Each fatty acid forms an ESTER bond with glycerol in a CONDENSATION REACTION
4. Glycerol molecule is same in all moleculets but there are variations in the fatty acids meaning there are different properties
  1. Saturated = NO carbon-carbon double bonds
  2. Mono-unsaturated = 1 double bond
  3. Polyunsaturated = More than 1 Double bond
5. High ratio of energy-storing Carbon-hydrogen bonds to carbon atoms = excellent source of energy
6. Low mass to energy ratio = good storage molecules. Beneficial to animals as reduced mass to carry around
7. Large, non-polar and insoluble = doesn't effect osmosis in cells or water potential in them
8. Triglycerides release water when oxidised, meaning they're an important source of water for organisms, especially those living in dry conditions
PHOSPHOLIPIDS
1. Similar to triglycerides but one fatty acid replaced with a PHOSPHATE MOLECULE
2. Fatty acid molecules - Hydrophobic 'tail'
  1. Phosphate Molecules - Hydrophillic 'head'
3. Polar
4. Properties
  1. Polar so form a bilayer between intercellular and extra cellular
  2. Phospholipid structure allows them to form glycolipids by combining with carbohydrates within the cell-surface membrane. These glycolipids are important in cell recognition
Characteristics
1. Contain: Carbon, Oxygen and Hydrogen
2. Proportion of oxygen to carbon and hydrogen is smaller than in carbohydrates
3. Soluble in solvents such as alcohols and acetone
4. Insoluble in water
Roles of Lipids
1. Source of Energy
  1. When oxidised, lipids provide over 2x the energy of carbohydrates
2. Waterproofing
  1. Lipids are insoluble = good at waterproofing.
    1. Both plants and insects have waxy, lipid cuticles that conserve water. Where as mammals produce an oily secretion from the sebaceous glands in the skin
3. Insulation
  1. Fats are slow conductors of heat meaning when stored they help retain body heat. They also act as electrical insulators in the myelin sheath around nerve cells
4. Protection
  1. Fat is often stored around delicate organs
Testing For Lipids
1. Dry and grease-free testube
  1. Add sample and ethanol
    1. Shake tube throughly and dissolve lipid in sample
      1. Add water, shake gently
        Cloudy white = lipid present and emulsion formed
        As a control, repeat the procedures using after instead of the sample; the final solution should be clear

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	Created by Bee Brittain about 9 years ago

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