Lipids

• Test for Lipids

  -crush the test material or place in solution

  -Mix with ethanol THEN water

  -White emulsion forms if lipids present
• Triglyceride structure

  -3 fatty acid chains joined to a glycerol

  -Each fatty acid joined by an ester bond formed by condensation reaction

  -Fatty acids can have varying lengths
• Saturated vs unsaturated

  Saturated- No C-C double bonds (usually animal fat)

  Unsaturated- one or more C-C double bonds causing kinks in the fatty acid tails (usually plant fat)
• Phospholipid structure

  -2 Fatty acids joined to glycerol+phosphate head by ester bonds

  -Hydrophilic head (phosphate+glycerol)

  -Hydrophobic fatty acid tails

  -Polar molecule
• TG vs PL

  Sim:

  -both have glycerol and fatty acids

  -both have ester bonds

  -both insoluble in water

  -both made of CHO

  Differences:

  -TG has 3 FA, PL has 2 FA

  -PL has a phosphate, TG doesn't

  -TG are fully non-polar whereas PL is polar
• Functions of lipids

  -Plasma membranes- flexibility/transfer of lipid-soluble substances through the phospholipid bilayer

  -Energy source- oxidised to make fuels- triglycerides have long CH tails to store lots of energy

  -Waterproofing- insoluble in water - TG dont affect water potential and PL form micelles in water