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LIPIDS

LIPIDS. L ipids classification. LIPIDS Insoluble in water Soluble in organic solvents. HYDROLYSABLE Waxes Oils Fats. NON HYDROLYSABLE Prostaglandins Terpenes Steroids. HYDROLYSABLE LIPIDS. Esters of long chain carboxylic acids and long chain alcohols

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LIPIDS

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  1. LIPIDS

  2. Lipids classification LIPIDS Insoluble in water Soluble in organic solvents HYDROLYSABLE Waxes Oils Fats NONHYDROLYSABLE Prostaglandins Terpenes Steroids

  3. HYDROLYSABLE LIPIDS • Esters of long chain carboxylic acids and long chain alcohols • Even number of carbons in both chains Waxes Triacontyl hexadecanoate - component of beeswax

  4. Lipids classification HYDROLYSABLE LIPIDS (fats and oils) PHOSPHOLIPIDS GLYCERIDES PHOSPHOGLYCERIDES SPHINGOLIPIDS

  5. GLYCERIDES Triacylglycerols (TAG) Principal components of animal fats and plant oils sn-1 sn-2 sn-3 R, R’, R’’ – alkyl chains C11 – C19 of saturated and unsaturated fatty acids

  6. Saturated fatty acids

  7. Arachidic acid Molecular shape of the most stable extended conformation

  8. Fatty acids biosynthesis - Priming reactions

  9. Fatty acids biosynthesis – Chainelongation cycle

  10. Unsaturated fatty acids C18

  11. Molecular shapes of unsaturated fatty acids Oleic acid -Linolenic acid

  12. Unsaturated fatty acid C20

  13. Comparison of fatty acids molecular shapes

  14. Melting points of fatty acids

  15. Glycerides – structure and properties Trimyristin Saturated, solid Unsaturated triglycerides have lower melting points because their unsaturated fatty acids do not pack so tightly as saturated chains Triolein Unsaturated, liquid

  16. Fatty acid composition of some fats and oils • (% by weight) Saturated acids Unsaturated acids

  17. Reactions of glycerides Saponification (alkaline hydrolysis) Soap

  18. Soap is the oldest detergent H2O H2O H2O H2O H2O H2O H2O OIL OIL H2O H2O H2O H2O H2O H2O H2O H2O H2O H2O A soap micelle solubilizes an oil drop in water Calcium salts of fatty acids precipitate from water

  19. Synthetic detergents act similarly Hydrophobic tail Hydrophilic head Advantage – calcium or magnesium ions in hard water do not destroy micelle cleaning capacity by salt precipitation

  20. Reactions of glycerides Transesterification (alcoholysis) Mixture of fatty acids methyl esters • Reaction used for: • analysis of fatty acids composition in fats (GC), • „biodiesel” manufacturing

  21. Reactions of glycerides Hydrogenation Triolein 2-oleoyl-1,3-distearoylglycerol Margarine production from plant oils

  22. PHOSPHOLIPIDS PHOSPHOGLYCERIDES SPHINGOLIPIDS Phospholipids – major lipid components of cell membranes in plants and animals

  23. PHOSPHOGLYCERIDES LECITHINS (choline derivatives) CEPHALINS (ethanolamine derivatives) R – usually saturated chain R’ – usually unsaturated chain

  24. Lipid bilayer forming cell membranes 50 A

  25. SPHINGOLIPIDS Sphingomyelin – coating around nerve fibres

  26. NONHYDROLYSABLE LIPIDS PROSTAGLANDINS TERPENES STEROIDS

  27. PROSTAGLANDINS • Synthesized in nature from arachidonic acid • Numerous biological activities • Lowering blood pressure • Affecting blood-platelet aggregation • Affecting kidney function • Lowering gastric secretions • Controlling inflammation • Affecting reproductive system • Stimulating uterine contractions during childbirth • Prostacyclin, tromboxane, leukotriene - closely related to prostaglandins, also biologically active • Extensively studied by medicinal chemistry

  28. TERPENES • Synthesized in plants • Small, volatile molecules • Immense diversity of structure • Could be isolated by steam distillation • Distillates known as essential oils • Used since ancient times as medicines, • spices, perfumes Patchouli alcohol

  29. ISOPRENE – structural motif of terpenes and steroids Head Tail In terpenes and steroids (isoprenoids) isoprene units are linked „head to tail”

  30. In terpenes isoprene units are linked „head to tail” Tail Head

  31. In terpenes isoprene units are linked „head to tail” Head Tail

  32. CLASSIFICATION OF TERPENES

  33. β-Carotene (red plant pigment) is tetraterpene (C40) Tail Tail Vitamin A precursor -Carotene is oxidatively splitted (by enzyme) at „tail-to-tail” bond yielding aldehyde called retinal, which is a vitamin A.

  34. BIOSYNTHESIS OF TERPENES IPP – isopentenyl pyrophosphate DMAPP – dimethylallyl pyrophosphate GPP – geranyl pyrophosphate FPP – farnesyl pyrophosphate GGPP – geranylogeranyl pyrophosphate

  35. Formation of cyclic monoterpenes from geranyl pyrophosphate

  36. BIOSYNTHESIS OF CHOLESTEROL Squalene (triterpene, C30) Cholesterol - steroid

  37. BIOSYNTHESIS OF STEROIDS 10 steps H H H H

  38. STEROID CONFORMATIONS An A,B trans steroid An A,B cis steroid

  39. STEROID CONFORMATIONS trans An A,B trans steroid cis An A,B cis steroid Cyclohexane rings have chair conformations but are unable to undergo ring-flips

  40. CHOLESTEROL CONFORMATION

  41. STEROID HORMONES Male sex hormones

  42. STEROID HORMONES Female sex hormones

  43. STEROID HORMONES Adrenocortical hormones A mineralocorticoid A glucocorticoid

  44. SYNTHETIC STEROIDS A synthetic estrogen A synthetic progestin Components of oral contraceptive pills

  45. ANABOLIC STEROIDS Both steroids have strong tissue-building effect

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