Lipids

• Lipid properties :

  
  

  insoluble in water

  only soluble in organic solvents
• Lipids are made up of carbon, hydrogen and oxygen
• Triglycerides : 1x glycerol , 3x fatty acids
• Triglycerides functions :

  
  

  long term energy source

  waterproofing

  organ protection

  insulation
• An ester bond is formed when a condensation reaction happens between glycerol and a fatty acid
• phospholipid : 1x phosphate group , 1x glycerol , 2x fatty acids
• Phospholipid have the same functions as triglycerides but the phosphate group allows it to

  be a cell surface membrane component
• phosphate group is negatively charged therefore its hydrophilic
• fatty acids are non-polar so they are hydrophobic
• lipid bilayer is made of phospholipids
• Test for lipids in a sample :

  1. Dissolve solid samples in ethanol
  2. add an equal volume of water and shake
  3. positive result: milky white emulsion forms
• triglycerides are formed from a condensation between 1 molecule of glycerol & 3 fatty acids which forms an ester bond
• saturated fatty acids:

  • contain only single bonds
  • straight chain molecules , many contact points
  • solid at room temperature
  • found in animal fats
• unsaturated fatty acids:

  • contain C=C double bonds
  • 'kinked ' molecules , have fewer contact points
  • liquid at room temperature
  • found in plant oils
• triglycerides have high energy:mass ratio

  = high calorific value from oxidation ( energy storage )
• triglycerides are an insoluble hydrocarbon chain

  = cells used for waterproofing
• triglycerides are slow conductors of heat

  = thermal insulaation
• triglycerides are less dense than water

  = buoyancy of aquatic animals
• phospholipids form a bilayer in water
• Both in phospholipids and triglycerides :

  • both may b attached to a mixture of saturated, monusaturated & polyunsaturated fatty acids .
  • both contain the elements C, H O
  • both formed by condensation reactions
• contrast phsopholipids and triglycerides :

  Phospholipid :

  • 2 fatty acids & 1 phospphate group attache
  • hydrophylic head & hydrophobic tail
  • used primarily in membrane formation

  triglycerides :

  • 3 fatty acids attached
  • entire molecule is hydrophobic
  • used primarily as a storage molecule
• phospholipids and triglycerides are macromolecules , a small repeating unit
• an ester bond is formed in a phospholipid molecule through a condensation reaction between glycerol and fatty acid