Lipids

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Lipids

  1. 1. LipidsFunction5 classes / types
  2. 2. Lipid Function1. Long-term energy storage (fat)2. Form cell membrane (phospholipids)3. Messaging (hormones)4. Insulation5. Cushioning of Internal Organs
  3. 3. Lipid FunctionWhy are lipids well suited for long term energy storage? Contain many high energy bonds between carbon and hydrogen Contain twice as much energy per gram than carbohydrates (very concentrated) Thus a much more compact form of storage than carbohydrate Animals store fats in adipose cells
  4. 4. Types of Lipid1. Fat: Triglyceride / triacylglycerol2. Phospholipid3. Steroid4. Wax5. Carotenoid
  5. 5. 1. Fat Structure Fatty acid also known as Glycerol Fatty acid triglyceride or Fatty acid triacylglycerol Consists of:  1 glycerol backbone  3 fatty acid chains
  6. 6. Glycerol Structure Fatty acid Basic structure: Glycerol Fatty acid  3 carbon molecule Fatty acid  each carbon has a hydroxyl group attached the alcohols are sites for condensation reactions
  7. 7. Fatty acid structure Basic structure:  Unbranched chain of carbons  A carboxyl group at one end Fatty acid chains can differ from each other in two ways:  Length of carbon chain: 4-24  Saturation (number of double bonds) - Saturated - Monounsaturated - polyunsaturated
  8. 8. Properties of Fatty acids Type Saturated Unsaturated Structure Single bonds Double bonds, kinkState at r.t. Solid liquid Origin Animals PlantsExamples Butter, lard Olive oil, essential FA (omega-3/6 fish oil)
  9. 9. Property of Saturated Fats  Saturated fats are solid!  Butter sculpture at the CNE 2012  Can you guess who this is?
  10. 10. Forming a triacylglycerol Condensation reaction between:  Hydroxyl on glycerol  Carboxyl on fatty acid Results in an ester bond Fig 5.10
  11. 11. Triacylglycerol model
  12. 12. 2. Phospholipid structure Phosphate / Polar  Glycerol backbone Glycerol group Fatty acid  2 fatty acids chains Fatty acid  phosphate/polar group
  13. 13. 2. Phospholipid structure Polar head: negatively charged, hydrophilic tail Nonpolar tails: fatty acids, hydrophobic Amphipathic: exhibiting both hydrophilic and hydrophobic properties
  14. 14. Polar Head Groups
  15. 15. Polar Head Groups
  16. 16. Self-assembly of phospholipid Condition: in water (aqueous) Self-assembly = spontaneous aggregate Due to hydrophobic interactions Micelle: single layer of phospholipid with polar head facing out, nonpolar tails facing inward Fig. 5.13 http://www.bio.miami.edu/~cmallery/255/255chem/mcb2.20.micelle.jpg
  17. 17. Self-assembly of phospholipid Phospholipid bilayer have a double layer of phospholipids where the nonpolar tails aggregate forming a hydrophobic core This is the basic structure of the plasma membrane http://www.bio.miami.edu/~cmallery/255/255chem/mcb2.20.micelle.jpg
  18. 18. Plasma Membrane Membranes are made of a bilayer of phospholipids.
  19. 19. Plasma Membrane
  20. 20. Phospholipid Bilayer
  21. 21. 3. Steroid Carbon skeleton, 4 interconnected rings Three 6C rings, one 5C ring Common examples:  cholesterol  hormones – estrogen, testosterone
  22. 22. SteroidCholesterol TestosteroneCortisone Aldoesterone
  23. 23. 4. Wax StructureLong chain hydrocarbons Primarily wax esters: a long chain hydrocarbon with an ester group that is not a triglyceride Could also involve alcohol, aldehyde & ketone groups http://www.lipidlibrary.co.uk/Lipids/waxes/index.htm
  24. 24. Properties of Wax Solid at room temperature Becomes liquid when melted has plastic properties: deforms under pressure without application of heat thermoplastic is a polymer that turns to a liquid when heated and freezes to a very glassy state when cooled sufficiently
  25. 25. Natural WaxNatural Animal wax: beeswax, lanolin, shellac Vegetable waxes: soy, jojoba, carnauba Mineral waxes: petroleum (paraffin) from fossil fuelsSynthetic Polypropylene, Polyethylene
  26. 26. 5. Carotenoids Natural fat-soluble pigment Backbone: 40 carbon polyene chain with alternating single and double bonds terminated by cyclic end-groups
  27. 27. Polyene structure
  28. 28. Carotenoid: Plant Pigment Found in plants, algae, photosynthetic bacteria Pigment needed for photosynthesis e.g. beta-carotene in carrot http://i03.i.aliimg.com/img/pb/593/581/248/1273569425304_hz-myalibaba-web15.hst.dsl.en.alidc.net_2444.jpg
  29. 29. Carotenoid: use in animals Detecting light: e.g. retinal absorbs light in retina Serves as antioxidant: double bonds absorb excess energy from other molecules, protecting cells and tissues from damaging effects of free radicals Source for vitamin A http://home.caregroup.org/clinical/altmed/interactions/Images/Nutrients/vitAbetac.gif
  30. 30. What is common to all lipids? The 5 forms of lipids studied are not built upon any common monomer. What unified these lipids so that they are all classified under the ‘lipid’ category? In other words, what makes a lipid, a lipid?
  31. 31. HW Question Why is glycerol not classified as a triose (3C monosaccharide)? Explain how saturation in a fatty acid chain affects fluidity. Explain how the length of the fatty acid chain affects fluidity.

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