3.1.3 Lipids

3.1.3 Lipids

1. NOT POLYMERS

   • Not made out of repeating monomers but different components
     • Known as MACROMOLECULES

2. Soluble in alcohol

3. insoluble in water (water is polar)

   • whereas lipids are non polar

4. Contain

   • Larger amounts of C + H
   • Little O

5. 4 types of lipids

   • Glycolipids
     • Carb + lipid
       • Glycosidic bond holds them together
   • Triglycerides
     • Glycerol + fatty acids (3)
       • Glycerol has 3C backbone hence the name
       • Fatty acids - group of molecules which can vary
       • fatty acids - can be made OR ingested
         • ingested - "essential" fatty acids
     • Structure
       • Hydrocarbon tails ( Only C + H)
       • Carboxyl group (COOH)
         • they are called 'acid'
           • can donate the H⁺ ion from OH group
     • Types of Hydrocarbon chains
       • Saturated
       • Unsaturated
         • HAS double bond(s) between carbons
         • Polyunsaturated hydrocarbons
           • ⟩1 C=C bond
         • Intermolecular forces between unsaturated are not strong
           • as kinks in hydrocarbon chains due to C=C bonds
           • ∴ more kinks in the tails increases the fluidity + lowers the melting point
     • Functions
       • Energy source
         • ester bonds can be hydrolysed
           • Glycerol ➡ (Respiration) ➡H₂O + CO₂
           • Fatty acids ➡(Respiration)➡ H₂O + CO₂
       • Energy store
         • Insoluble
           • non polar
           • doesn't alter water potential
         • Low mass : energy
           • each unit of fat there is more energy than sugar fat ⟩ sugar
       • Insulation
         • whales have 'blubber'
         • fat reserves for hibernation
         • Mechanical protection
           • fat around organs
             • Humans - heart/kidneys
   • Phospholipids
     • Phospholipid bilayer
       • 2 layers of phospholipids
       • selectively permeable
         • small non polar molecules can go through
           • CO₂ , O₂
       • 20-80% of all surface membranes
         • bacteria contain higher % of proteins in membrane
       • Fluid Mosaic model
         • Has Stability as never have fatty acid chains on outside
         • Phospholipids can swap and move around ONLY laterally
       • Contain proteins / lipids/ glycoproteins
     • Structure
       • 2 hydrocarbon tails
       • glycerol
       • 1 phosphate containing group
     • Amphipathic
       • Half hydrophobic / half hydrophilic
     • Can create Micelles
   • Cholesterol
     • Steroid alcohol
     • lipid
     • 4 carbon 'ringed' structures
       • Isoprene units
     • Produced in the liver
     • Small
     • Hydrophobic
       • Controls the fluidity of bilayer
     • Plant Cholesterol
       • Stigmasterol
         • The difference it has double C=C between C₂₂=C₂₃
     • Used to make, testosterone, oestrogen + vitamin D
       • All small, non polar molecules

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