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Lipids

Lipids. Dr. Mamoun Ahram. Resources. This lecture Campbell and Farrell’s Biochemistry, chaper 8. Lipids. What are lipids? Classes Fatty acids Glycerides and waxes Phospholipids (glycerophospholipids and sphingolipids) Glycolipids Eicosanoids Steroids. Lipid Functions.

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Lipids

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  1. Lipids Dr. Mamoun Ahram

  2. Resources • This lecture • Campbell and Farrell’s Biochemistry, chaper 8

  3. Lipids • What are lipids? • Classes • Fatty acids • Glycerides and waxes • Phospholipids (glycerophospholipids and sphingolipids) • Glycolipids • Eicosanoids • Steroids

  4. Lipid Functions • Source of energy • Structural components (cell membranes) • Regulators of signaling, metabolism, and absorption • Precursors of hormone • Precursors of vitamins • Electric and tissue insulators • Shock absorbers

  5. Fatty acids • Lengths • Number of carbons • Short: 2-6, medium: 8-14, long: >14 (16-24) • Even vs. odd • Degree of unsaturation

  6. Amphipathic molecules • They are an excellent examples of amphipathic molecules

  7. Types of fatty acids • Saturated fatty acids • Unsaturated fatty acids • Monounsaturated • Polyunsaturated

  8. Cis vs. trans bonds Cis > trans

  9. At physiological pH • Carboxylate form not carboxylic acid form • For example, palmitic acid

  10. Greek number prefix

  11. Naming of a fatty acid • Alkane to oic • Octadecane (octa and deca) is octadecanoic acid • One double bond = octadecenoic acid • Two double bonds = octadecadienoic acid • Three double bonds = octadecatrienoic acid

  12. More on naming(Designation of carbons and bonds) • 18:0 = a C18 fatty acid with no double bonds • stearic acid (18:0) • palmitic acid (16:0) • 18:2 = two double bonds • linoleic acid

  13. More on naming(designation of location of bonds) • Where do numbering start at? • Δn: The position of a double bond • cis-Δ9 :a cis double bond between C 9 and 10 • trans-Δ2:a trans double bond between C 2 and 3

  14. Another way of naming • (ω)-C: distal methyl C as #1

  15. Essential fatty acids • Linoleic acid and linolenic acid • Linoleic acid is the precursor of arachidonates • Linolenic acid is the precursor of EPA and DHA

  16. Arachidonate • all cis-Δ5,Δ8,Δ11,Δ14-eicosatetraenoate, CH3(CH2)4(CH=CHCH2)4(CH2)2COO-

  17. Eicosanoids

  18. Synthesis of eicosanoids

  19. Functions • Prostaglandins • Inhibition of platelet aggregation • Blood clotting • Leukotrienes • Constriction of smooth muscles • Asthma • Thromboxanes • Constriction of smooth muscles • Platelet aggregation • Prostacyclins • An inhibitor of platelet aggregation • A vasodilator

  20. Aspirin

  21. Omega-3 PUFAs • α-linolenic acid eicosapentaenoic acid (EPA) docosahexaenoic acid (DHA) • Clinically speaking • Reduce inflammatory reactions by • Reducing conversion of arachidonic acid into eicosanoids • Promoting synthesis of anti-inflammatory molecules • Brain development and function http://supplementscience.org/pufas.html

  22. Omega -6 PUFAs • Arachidonic acid • stimulate platelet and leukocyte activation, • signaling of pain, • induction of bronchoconstriction, • regulation of gastric secretion

  23. Clinical Significance of omega -9 FAs • Oleic acid • Reducing cholesterol in the circulation

  24. Properties of fatty acids • The properties of fatty acids are dependent on chain length and degree of saturation

  25. Effect of double bonds

  26. Effect on membrane fluidity

  27. Effect of chain length

  28. Hydrogenation…partially

  29. Physiological importance of fatty acids • Building blocks of other lipids • Modification of many proteins (lipoproteins) • Important fuel molecules • Derivatives of important cellular molecules

  30. Triglycerides

  31. Types of glycerides How soluble will a triglyceride be if fatty acids are unsaturated?

  32. Waxes

  33. Other lipids • Phospholipids • Sphingolipids • Glycolipids • Steroids

  34. Phospholipids (phosphoacylglycerols)

  35. Other phospholipids • Phosphatidylcholine • lecithin • most abundant membrane lipid • Phosphatidylethanolamine • Phosphatidylserine • abundant in brain • Phosphatidylinositol • sends messages across cell membranes

  36. Emulsification

  37. Plasmalogens • Precursor: Dihydroxyacetone phosphate

  38. Major classes of plasmalogens • Ethanolamine plasmalogen (myelin) • Choline plasmalogen (cardiac tissue) • Platelet activating factor • Serine plasmalogens

  39. Platelet activating factor (PAF) • PAF is a potent biochemical signal molecule • cause platelet aggregation and vasoconstriction (via release of serotonin from platelets) • involved in smooth muscle contraction, inflammation, and allergic response • Note the short (acetate) fatty acyl chain at the C-2 position in PAF

  40. Types of lipid structures

  41. Uses of liposomes

  42. Sphingolipids

  43. Ceramide

  44. Types of sphingolipids • The sphingolipids are divided into the two subcategories: • Sphingomyelins • Glycosphingolipid (or glycolipids)

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