Lipids

• What are the 4 roles of lipids?

  Source of energy - when oxidised produce twice the energy the same mass of carbohydrates make and they release H20

  Waterproofing - hydrophobic, insoluble in water

  Insulation - Slow conducters of heat- when stored below the surface of the body they retain heat and also inulate neurons

  Protection - Fat is stored around delicate organs e.g kidneys
• What is the structure of a triglyceride?

  Once glycerol molecule undergoes a condensation reaction with 3 fatty acid molecules to create ester bonds between the glycerol and fatty cids.

  
• What part of a fatty acid makes the formation of an ester bond possible?

  Fatty acids are carboxylic acids so contain a COOH functional group
• Where does the ester bond form|?

  between the hydroxyl group (OH) on the glycerol molecule and the the carboxyl group (COOH) on the fatty acid
• What does a saturated fatty acid mean?

  The hydrocarbon chain only has carbon to carbon single bonds

  
• What does unsaturated fatty acid mean?

  The hydrocarbon chain has at least one carbon t carbon double bond.

  Ths creates a kink in the structure therefore the molecule can not be packed at tightly causing it to be liquid at RTP

  
• What is a cis-fatty acid

  A form of an unsaturated fatty acid that has the hydrogens lying on the same side of the carbon-carbon double bond. they are metabolised by enzymes
• What is a trans-fatty acid

  A form of an unsaturated fatty acid that has the hydrogens lying on opposite sides of the carbon-carbon double bond. it can not form an enzyme-subrtrate complex so is not metabolised by enzymes
• What are the properties of trigycerides?

  1. can store lots of energy due to large ratio between energy storing carbon-hydrogen bonds to the number of carbon atoms.

  2. Metabolic water source which is essential to dessert animals due to the fact they release H2O whe oxidised

  3. Insoluble so dont affect water potential or osmosis due to being hydrophobic and non-polar molecules

  4. Can be stored without increasing mass and preventing due to their relatively low mass.
• What does monounsaturated mean?

  only one carbon-carbon double bond
• What does polyunsaturated mean?

  many carbon-carbon double bonds
• What is the structure of a phospholipid

  glycerol, two fatty acids, and a phosphate group
• draw a phospholipid

  
• How do phospholipids form? what is the reaction called? what are the bonds formed called?

  condensation reaction that releases H20 molecules, forms ester bonds
• What does the term amphipathic mean

  having both hydrophilic and hydrophobic parts
• How is a phospholipid amphipathic

  it has a polar head due to the phosphate ion and non polar fatty acid tails
• due to being amphipathic what structure can phospholipids form

  form a bilayer in call membranes which acts as a barrier to water soluble molecules
• draw a phospholipid bilayer

  
• How do triglycerides and phospholipids compare?

  Both have a glycerol molecule

  Both form by condensation reaction

  Both form 3 ester bonds so both release 3 H20 molecules

  Phospholipids contain 2 fatty acid tails whereas triglycerides contain 3

  the main function of triglycerides is energy storage whereas the main function of a phospholipid is as a cell membrane component

  triglycerides are non polar and hydrophobic so are insoluble, phospholipids have a polar head which is hydrophilic so attracts water