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Chemistry of Lipids

Chemistry of Lipids. Dr ANITHA 1. Lipid chemistry. Lipid chemistry. Definition Organic substances insoluble in water but soluble in organic solvents like chloroform, ether and benzene Fatty acids are the building blocks

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Chemistry of Lipids

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  1. Chemistry of Lipids Dr ANITHA 1

  2. Lipid chemistry

  3. Lipid chemistry Definition • Organic substances insoluble in water but soluble in organic solvents like chloroform, ether and benzene • Fatty acids are the building blocks 3

  4. Classification of Lipids ( modified Bloor)

  5. Simple lipid They are esters of FA with alcohols D/U the type of alcohols these are subclassified as

  6. 6

  7. Waxes True waxes Esters of FA with long chain alcohols other than glycerol • Lanolin • Bees wax • Spermacetic oil 7

  8. Classification of Lipids 8 8

  9. These are esters of FA with alcohol containing additional[prosthetic] groups. • Complex lipid Subclassified according to the type of prosthetic group 9

  10. These are esters of FA with alcohol containing additional[prosthetic] groups. • Complex lipid Subclassified according to the type of prosthetic group 10

  11. 1.Phosholipids FA + ALCOHOL + PHOSPHORIC ACID and nitrogenous base 11

  12. 1.Phosholipids Phospholipids may be classified on the basis of the type of alcohol present 13

  13. A. Glycerophospholipids • B. Spingophospholipids Alcohol is GLYCEROL Alcohol is SPINGOSINE • Phosphatidylcholine or lecithin • Phosphatidyl serine • Phosphatidylinositol • Spingomyelin

  14. 2.Glycolipids FA + ALCOHOL[SPINGOSINE] +CARBOHYDRATE (glycosphingolipids) • They do not contain phosphate group • Example • Cerebrosides • Gangliosides • Globosides

  15. Lipid with prosthetic group PROTEIN • 3.Lipoproteins • Chylomicrons • Very low density lipoprotein (VLDL) • Low density lipoprotein (LDL) • High density lipoprotein (HDL)

  16. Include the products obtained after the hydrolysis of simple and compound lipids • Derived lipids

  17. Functions of Lipids • Concentrated storage form of energy • Structural lipids like phospholipids and cholesterol – cell membrane and regulate permeability • Precursor of many steroid hormones, vitamin D • Act as thermal insulator for internal organs and give shape and smooth appearance to body • Lipids are activators of enzymes • Lipoproteins – transportation of lipids

  18. Functions of Lipids • Helps in absorption of fat soluble vitamins • phospolipids serve as surfactants by reducing surface tension, detergents and emulsifying agents • Phospholipids present in inner mitochondrial membrane participate in ETC • Lipids present in myelinated nerves act as insulators for propagation of depolarization wave.

  19. Medical Importance of lipids Obesity : • Excessive deposition of fat in adipose tissue. Abnormality in cholesterol metabolism leading to myocardial infarction. 2. Atherosclerosis: 3. Ketosis : Derangement in the metabolism of fatty acid in type-1 Diabetes mellitus.

  20. Fatty Acids They are acids derived from fats. • They are carboxylic acids containing long hydrocarbon side chain • Animal FA are simpler when compared to plants • Present mainly in esterified form eg PL, TAG , GL • In plasma found bound to albumin called non esterified FA or FFA Based on the nature of hydrocarbon side chain, they are divided into: A. Saturated fatty acids B. Unsaturated fatty acids

  21. Saturated fatty acids (no double bonds).

  22. Unsaturated fatty acids • One or more double bonds are present. Subclassified according to number of double bonds 25

  23. Fatty acids are also divided based on hydrocarbon chain length. 27

  24. Chemistry of Lipids 2 Dr ANITHA

  25. Lipid chemistry

  26. Numbering of carbon atoms in FA C system and n or ω system 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH2-COOH Palmitic acid ω or n β α Carboxyl end Methyl end 28

  27. Nomenclature of Fatty Acids Saturated fatty acids Saturated FA have both trivial names and systematic names. Usually saturated FA end as anoic acids.

  28. Nomenclature of Fatty Acids Unsaturated fatty acids Usually Unsaturated FA end as enoic acids.

  29. Nomenclature of Fatty Acids Unsaturated fatty acids Representation of double bonds of FA 2 systems

  30. 1. C-System • 2. ω-or n-System 18 17 16 15 14 13 12 11 10 9 8 1 CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH=CH-(CH2)7 -COOH Oleic acid (C:18:1:∆9) 1 2 3 4 5 6 7 8 9 10 11 18 CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH=CH-(CH2)7 -COOH Oleic acid (C:18:1:ω-9)

  31. ESSENTIAL FATTY ACIDS 34 Can’t be synthesised in human body Linoleic acid ω-6, Linolenic acid ω- 3 and Arachidonic acid ω - 6(PUFA) Arachidonic acid can be synthesied from Linoleic acid Linoleic acid : safflower oil, sunflower oil, soyabean oil. Linolenic acid : Linseed oil, Soyabeen oil. Arachidonic acid : animal phospholipids, ground nut oil.

  32. Importance / Functions of Essential Fatty acids 1. Precursors of Eicosanoids which are local hormones (eg. Prostaglandins) 2.Help in lipid transport( EFA – PL – LP) 3. lowers serum cholesterol level. Antiatherogenic effect 4. As constituents of cell membrane 5.Prevent fatty liver ( lipotropic effect ) 6.Normal reproductive function 7.Normal epidermal growth 8. omega-3 FA(docosahexanoic acid(DHA) or cervonic acid ) reqd. for brain ,development of visual system, protective role against atherosclerosis and cardiovascular disease.

  33. EFA deficiency Occurs if EFAs are excluded from diet for long periods Seen mainly in children and infants fed on low fat milk formula. Rarely seen in adults, except in patients maintained on prolonged IV nutrition low in essential fatty acids. The syndrome in humans characterized by • Dermatitis • Poor wound healing • (phrynoderma/toad skin )

  34. Triglyceride

  35. Triglycerides-Non polar , water insoluble , neutral fats . 41 O CH2-O-C-R1 O R2-C- O- CH O CH2-O-C-R3 Major bulk of body lipid. Functions - Stored in adipose tissue; Reserve Fuel, concentrated forms of energy heat insulator & shock absorbing cushion Types

  36. STORAGE LIPIDS/ACYL GLYCEROL • FATTY ACID – ACYL GROUP • TRIACYLGLYCEROL TSSIMPLE TAG MIMIXED TAG 42

  37. STEREOSPECIFIC NUMBERING OF GLYCEROL C1 C3 43

  38. 44 Properties of triacylglycerol OOOfunsat fatty acid is called hardening in the presence of a catalyst (nickel).its a commercially valuable method of converting oils (liquid) of plant origin into solid fats as margarines, vegetable ghee, etc. Hydrogenation increases the shelf life and prevents rancidity of the fat. AUTO OXIDATION –RANDICITY AND DAMAGE TO TISSUES PREVENTED BY ANTIOXIDANTS

  39. Tests for purity of fat

  40. Chemistry of Lipids 3 Dr ANITHA

  41. Lipid chemistry

  42. Structural Lipids or Membrane Lipids The 3 major kind of membrane lipids are

  43. 1.Phosholipids FA + ALCOHOL + PHOSPHORIC ACID 47

  44. 1.Phosholipids PLs are the major lipid constituents of cellular membranes 40% of the lipids in RBC membrane and over 75% of lipids in the inner mitochondrial membrane PLs are amphipathic in nature

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