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  1. 1. lipids
  2. 2. What are lipids? <ul><li>Lipids are a a large and varied group of organic compounds. </li></ul><ul><li>Lipids contain carbon, hydrogen and oxygen. </li></ul><ul><li>They are insoluble in water but will dissolve in organic solvents. </li></ul><ul><li>There are two types of lipids: fats which are solid at room temp and oils which are liquid at room temp. </li></ul>
  3. 3. Triglycerides. <ul><li>Triglycerides are made up of a molecule of glycerol join with three fatty acids (RCOOH). </li></ul><ul><li>H H </li></ul><ul><li>H C OH HOOC.R H-C-OOC.R </li></ul><ul><li>H C OH + HOOC.R H-C-OOC.R </li></ul><ul><li>H C OH HOOC.R H-C-OOC.R </li></ul><ul><li>H H </li></ul>WATER
  4. 4. Ester bond
  5. 5. Ester bond. <ul><li>Triglycerides are formed when a glycerol molecule is linked to 3 fatty acid molecules. </li></ul><ul><li>Fatty acids always have –COOH group (carboxyl group) and this combines with the –OH group on the glycerol by a condensation reaction. </li></ul><ul><li>When this happens an ester bond is formed. </li></ul>
  6. 6. Ester bond
  7. 8. UNSATURATED FATTY ACIDS. <ul><li>Unsaturated fatty acids have double bonds between some of the carbon atoms. </li></ul><ul><li>Unsaturated fatty acids have a low melting point and may be liquid at room temperature. </li></ul><ul><li>Plant oils are an example of an unsaturated triglyceride that is a liquid at room temperature. </li></ul>
  8. 9. Structure of a unsaturated fatty acid. <ul><li>O H H H H H H H H H H H H H H </li></ul><ul><li>C-C-C-C-C-C-C-C=C-C-C-C-C-C-C-H </li></ul><ul><li>HO H H H H H H H H H H H H H H </li></ul><ul><li>In unsaturated fatty acids at least some of the carbon atoms are joined by a double covalent bond. </li></ul>
  9. 10. Structure of a saturated fat. <ul><li>Saturated fatty acids do not have a double bond between the carbon atoms. </li></ul><ul><li>Saturated fatty acids have a higher melting points and are solid at room temperature. </li></ul><ul><li>Animal fats are classified as a saturated fatty acid. </li></ul>
  10. 11. A saturated fatty acid molecule. <ul><li>O H H H H H H H H H H H H H H </li></ul><ul><li>C-C-C-C-C-C-C-C-C-C-C-C-C-C-C-H </li></ul><ul><li>HO H-H-H-H-H- H-H-H-H-H-H-H-H-H </li></ul><ul><li>In saturated fats the carbon molecules are join together by single covalent bonds. </li></ul>
  11. 13. Phospholipids. <ul><li>A Phospholipid molecule is like a triglyceride in which one of the fatty acids have been replaced by a phosphate group. </li></ul><ul><li>The phosphate group gives the phospholipid a hydrophilic head and a hydrophobic tail. </li></ul>
  12. 14. Phospholipids have two ends. <ul><li>A head that contains a phosphate group. This has an uneven charge that makes the head able to mix with water (hydrophilic). </li></ul><ul><li>A tail that contains 2 fatty acid chains. They have an even charge and this makes them unable to mix with water (hydrophobic). </li></ul>
  13. 15. Structure of a phospholipid. A phosphate group
  14. 18. Hydrophilic head Hydrophobic tail A phospholipid molecule
  15. 19. Test for lipids. (The emulsion test) <ul><li>Lipids do not dissolve in water, but they will dissolve in ethanol. </li></ul><ul><li>Add ethanol to the sample being tested. </li></ul><ul><li>Shake the sample and ethanol, so that the lipids dissolve </li></ul><ul><li>Pour the mixture of ethanol and sample into water. </li></ul><ul><li>If lipids are present the water turns cloudy as a white emulsion is formed. </li></ul>