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2009-12-05 13:12:54
chemistry lipids

chemistry test 4 lipids
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  1. Lipids
    • • Lipids can be broadly classified as biomolecules which are insoluble in water – they contain a high percentage of non-polar hydrocarbon regions.
    • • They exists as colloidal suspensions within the aqueous fluid of the organism
    • • They are responsible for long term energy storage, building cell membranes, emulsification ofnutrients and protection of internal organs.
    • • They can be further classified as – fatty acid derived (waxes, fats, prostaglandins) – steroids
  2. Long hydrocarbon chain (10-20 C atoms, non-polar, water insoluble
    • If the hydrocabon chain contains all single bonds, then the fatty acid
    • is saturated
    • If the hydrocarbon chain contains a double bond, the fatty acid is
    • mono-unsaturated
    • If the hydrocarbon chain contains several double bonds, the fatty
    • acid is poly-unsaturated.
  3. Fats and Oils
    Fats are solids, Oils are liquid
    • • Consist of triglycerol backbone and three fatty acids linked through oxygen atoms
    • • Fats – Saturated- all C-C bonds are single bonded.
    • • These type of fats contain the maximum of H atoms possible per carbon atom (the carbons are filled, or ‘saturated’ with H atoms – Unsaturated – some of the carbon atoms are joined with double bonds.
    • • In principle, more H atoms can be added to these C atoms
  4. Key Points
    • • The more double bonds (unsaturation) in the chain, the lower the melting point
    • – saturated fatsoften solid at room temp.
    • – mono unsaturated  liquid at room temp, but will solidify in refrigerator
    • – poly unsaturated lowest melting points saturated fats can "pack" efficiently
    • into a crystal structure cis double bonds make 'packing' inefficientdifficult to crystallize into solids. Therefore they remain liquid at room temp. • Cis double bonds predominate
  5. Key Points
    • • Humans can synthesize most fatty acids from carbohydrate feed stocks.
    • BUT
    • • Polyunsaturated acids are inefficiently synthesized
    • – obtained from external food sources
    • – referred to as "essential fatty acids"
  6. Omega Acids
    Omega-3 acids inhibit clotting of platelets in blood vessels, thereby perhaps providing protection against coronary disease.
  7. Fats and Oils
    • Fats and oils are the product of the reaction glycerol
    • with fatty acids
    • Fats are solids, while oils are liquids
    • Fats are also known as triglycerides
    • Fats are used by organisms for long term storage of energy
  8. Partially Hydrogenated Fats
    • • Formed by treating polyunsaturated vegetable fats with hydrogen
    • • Advantages
    • – Proper consistency for use as margarine and shortenings
    • – More resistant to oxidation and spoilage
    • • Disadvantages
    • – Formation of saturated fats bad cholesterol
    • – Formation of trans fatty acids. bad cholesterol
  9. Trans-Fatty Acids
    • Unsaturated fats have cis double bonds.
    • Trans-fatty acids are implicated in the formation of LDL cholesterol\
    • The hydrogenation process often leads to the formation of transfatty acids as an unwanted by-product
  10. Saponification
    • • Heating a fat with a strong base breaks the ester bonds
    • • The result is a sodium salt of the fatty acid
    • • These are called ‘soaps’
    • – hydrophobic chain (dissolves greasy matter)
    • – hydrophilic CO -Na+ end mixes with water 2
    • – results in dispersing of greasy matter (dirt) in water
  11. Glycerophospholipids
    • •Key points:
    • –they are consist of a glycerol backbone, two fatty acid chains and 1 ester of phosphoric acid and amino alcohol
    • – They contain a nonpolar region (fatty acid chain) and highly polar region (ionized nitrogen)
    • – most abundant lipid in cell membranes (walls).
    • – they assist in making cell membranes permeable so that molecules can enter and leave the cell
    Steroids are characterized by 4 ring system- 3 rings have 6 carbon atoms each (A-C); the D ring has 5 carbon atoms
  13. Steroid Hormones
    • Hormones are chemical messengers that signal between different cell types within the progesterone
    • (signals uterus prior to implantation of fertilized egg) norethindrone (contraceptive) organism.
  14. Steroids
    (Cholesterol and Steroid Hormones)
    • • Cholesterol is essential for animal life
    • – component of cellular membranes, myelin (nerve covering), brain and liver tissue
    • – precursor (starting material) for Vitamin A
    • – precursor for other hormones
    • • Obtained via diet or synthesis in the liver
    • – Diet
    • • animal products only (not present in plants)
    • – Synthesis in the liver
    • • from carbohydrates
    • • from fats (esp. saturated)
  15. Transport of Cholesterol
    LDL (low density lipoprotein)
    • – Transport to cells for membrane synthesis, steroid hormones and bile salts.
    • – If more LDL present than is needed for cell maintenance, LDL deposits cholesterol in lining of arteries heart disease, high blood pressure
    • – "bad cholesterol"
  16. Transport of Cholesterol
    • HDL (high density lipoprotein)
    • – function to pick up excess cholesterol and return it to the liver for breakdown and excretion.
    • – "good cholesterol"
    • • Recommended levels
    • – Total: <200mg/dL
    • – LDL: <130 mg/dL
    • – HDL: >40mg/dL