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Lipids chemistry reference


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lecture slides for chemistry of lipids

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Lipids chemistry reference

  1. 1. Lipids are a class of heterogenous compounds which are relatively insoluble in water and soluble in nonpolar solvents. Chemically: either esters of fatty acids or substances capable of forming such esters
  2. 2. BIOMEDICAL IMPORTANCE1. Stored as a source of energy in the body. Lipid (TGL) Droplets In Adipose tissue
  3. 3. 2. Structural components of biomembranes.
  4. 4. 3. Thermal Insulator : Provides insulation against changes in external temperature.
  5. 5. 4. Lipids act as electric insulators in neurons.
  6. 6. 5. Act as metabolic regulators (steroid hormones and prostaglandins).6. Act as surfactants and prevents collapse of lungs during expiration.7. Lipids are used as detergents.8. Lipids used in emulsification and intestinal absorption of non polar nutrients like fatty acids and fat soluble vitamins.9. Associated with diseases such as atherosclerosis, diabetes mellitus and obesity.10. Gives shape and contour to the body.
  7. 7. LIPIDS1. Simple 2. Compound Lipids 3. Derived LipidsLipids
  8. 8. 1. Simple LipidsEsters of fatty acids with various alcohols. a. Fats :esters of fatty acids with glycerol. eg: triglycerides. b. Waxes: esters of fatty acids with higher molecular weight monohydric alcohols. eg: beeswax Glycerol
  9. 9. 2. Compound LipidsEsters of fatty acids with various alcohols alongwith an additional group. Simple lipid + Additional group = Compound Lipids a. Phospholipids: b. Glycolipids: c. Other Complex Lipids:
  10. 10. COMPOUND LIPIDSEsters of fatty acids with various alcohols alongWith an additional group. Phospholipids Glycolipids OthersGlycerphospholipids -Phosphatidyl choline Cerebrosides Lipoproteins - Phosphatidyl ethanolamine Gangliosides Aminolipids - Phosphatidyl serine - Phosphatidyl inositol Globosides - Cardiolipin - PlasmalogensSphingophospholipids
  11. 11. 3. Derived LipidsLipid molecules derived from simple/compound lipidson their hydrolysis Fatty acids Eicosanoides Steroids Sterols Cholesterol Bile acids Vitamins (A,D,E,K) Ketone Bodies
  12. 12. SIMPLE LIPIDSNAME ALCOHOL ACID EXAMPLEFats Glycerol Fatty acid TriglyceridesWaxes Aliphatic / Fatty acid Bees wax Aromatic alcohol
  13. 13. Phospho lipids
  14. 14. NAME ALCOHOL ACID Po4 ADDITIONAL GROUPGLYCERO PHOSPHO LIPIDSPhosphatidyl Glycerol Fatty acid Po4 Cholinecholine(lecithin)Phosphatidyl Glycerol Fatty acid PO4 Ethanolamineethanolamine(cephalin)Phosphatidyl Glycerol Fatty acid PO4 SerineserinePhosphatidyl Glycerol Fatty acid PO4 MyoinositolinositolCardiolipin Glycerol Fatty acid PO4 Phosphatidyl glycerolPlasmologens Glycerol Fatty acid (ether PO4 Ethanolamine link at C1)SPHINGO PHOSPHO LIPIDS
  15. 15. Glycolipids NAME ALCOHOL ACID GLYCOSYL ADDITIONAL RESIDUE GROUP Cerebrosides Sphingosine Fatty acid Galactose/ (cerebronic Glucose acid) Gangliosides Sphingosine Fatty acid Glucose Sialic acid Globosides Sphingosine Fatty acid Glucose + Galactose Sulphatides Sphingosine Fatty acid Galactose SO3Note:Ceramide: Sphingosine + Fatty acid Slide 51
  16. 16. CLASSIFICATION OF FATTY ACIDSBased on ‘R’ group 1. Small / Medium / Long Chain Fatty Acids 2. Odd / Even Chain Fatty Acids 3. Saturated / Unsaturated Fatty AcidsNutritionally Essential / Non-Essential Fatty Acids
  17. 17. 1. Small / Medium / Long Chain Fatty AcidsSmall chain Fatty acids : 2 – 4 carbons Medium chain Fatty acids : 6 – 14 carbons Long chain Fatty acids : more than 16 carbons
  18. 18. 2. Odd / Even Chain Fatty Acids 12 11 10 9 8 7 6 5 4 3 2 113 12 11 10 9 8 7 6 5 4 3 2 1
  19. 19. Saturated Fatty Acids a) Even chain fatty acid eg., Palmitic acid Stearic acid a) Odd chain fatty acid eg., Propionic acidUnsaturated Fatty Acidsa) Mono unsaturated fatty acid (MUFA) eg., Oleic acidb) Poly unsaturated fatty acid (PUFA) eg., Linoleic acid, Linoleinic acid, Arachidonic acida) Eicosanoids
  20. 20. USES / FUNCTIONS OF PUFA Major components of membrane lipids Contributes to the fluidity of membranes Used for Prostaglandin synthesis Decreases the incidence of Atherosclerosis,Coronary Artery Diseases
  21. 21. Saturated fatty acids: rich in storage lipids (adipose tissue)Unsaturated fatty acids: rich in membrane lipids(to increase fluidity)
  22. 22. Based on Nutrition Essential Non essential
  23. 23. Essential Fatty AcidsFatty acids that can not be synthesized by body & has tobe supplied by dietEx: Linoleic acid Linolenic acid Arachidonic acidFunctions: Structural composition of Brain & Nervous system Precursor for Eicosanoid synthesis Prevents atherosclerosis Prevents skin lesions
  24. 24. 12 11 10 9 8 7 6 5 4 3 2 1ω ε δ γ β α Two types 1. ω – type 2. N - type
  25. 25. Indicating Number & Position of Double Bond 18:1,9 Δ9 18:1 ω3, ω6, ω9 Fatty Acids ω9,C18:1
  26. 26. Melting Point :• Temperature at which fats are converted from solid state to liquid state.• Saturated acids have high melting point than unsaturated acids• Increases with increase in hydrocarbon chain lengthSolubility: Decreases with increasing chain length Increases with temperature.Unsaturated fatty acids exhibit cis-trans isomerism
  27. 27. GEOMETRIC ISOMERISM OF OLEIC AND ELAIDIC ACIDS Natural Fatty acids – ‘cis’ form
  28. 28. 1. Salt Formation2. Esterification3. Hydrogenation4. Halogenation5. Hydrolysis6. Oxidation
  29. 29. 1. SALT FORMATIONR – COOH + NaCl R – COONa + HClFatty acids react with alkalies to form Salts of fatty acidsNa+ or K+ salts of fatty acids : Soaps
  30. 30. 2. ESTERIFICATION + +Most of the fatty acids of body are in esterified form
  31. 31. 3. HYDROGENATION (hardening) CH3 – CH2 – CH – CH – CH2 – COOH – H2 CH3 – CH2 – CH2 – CH2 – CH2 – COOHUnsaturated FA converted to Saturated FAUsed to synthesize Vanaspathi & MargaraineTrans Fatty acids are formed
  32. 32. 4. HALOGENATION CH3 – CH2 – CH – CH – CH2 – COOH – I2 CH3 – CH2 – CH – CH – CH2 – COOH I IThe amount of halogen taken by a fatty acid depends on No of double bonds Degree of unsaturation
  33. 33. TAG undergoes stepwise hydrolysis of its ester bonds toform Glycerol & Free Fatty acids LipasesDigestion of Fats in GITMobilisation of TGL from Adipose tissue
  34. 34. GLYCERO PHOSPHOLIPIDS Phosphatidic Acid
  35. 35. Choline PhosphatidylPhosphatidic acid Ethanolamine Serine Inositol Phosphatidyl Glycerol
  36. 36. Plasmalogens
  37. 37. Phosphatidyl Choline (LECITHIN) CholinePhosphatidic acid + CholineLecithin acts as lung surfactantMost abundant phospholipid of biomembranes
  38. 38. Phosphatidyl Choline (LECITHIN) Dipalmitoyl Lecithin – Lung surfactant.Synthesized by Alveolar type - II cells. Rich in alveolar fluid lining the alveoliReduces surface tension of alveolar fluid & prevents collapseduring expirationDeficiency in premature infants leads to collapse – Respiratory Distress syndrome
  39. 39. SITE OF ACTION OF PHOSPHOLIPASES Phospholipase A1Phospholipase A2 Phospholipase D Phospholipase C
  40. 40. SPHINGO PHOSPHOLIPIDS Sphingosine – alcohol moiety Commonly found in nerve tissues
  41. 41. SPHINGOPHOSPHOLIPIDS Sphingomyelin Sphingomyelin
  43. 43. 1. Structural components of cell membrane.2. Enable enzyme action.(mitochondrial enzyme system).3. Required for blood coagulation (prothrombin to thrombin, activation of factor 8 by factor 9).4. Transports lipids from intestine and liver.5. Choline acts as a lipotropic agent since it prevents the formation of fatty liver.6. Phospholipids of myelin sheath provides insulation around nerve fibers.
  44. 44. COMPOUND LIPIDSEsters of fatty acids with various alcohols alongWith an additional group. Phospholipids Glycolipids OthersGlycerphospholipids Cerebrosides AminolipidsSphingophospholipids Gangliosides Lipoproteins Sulfatides Globosides
  45. 45. o Lipids containing carbohydrate moiety - Glycolipidso Alcoholic component – Sphingosineo Ceramide – Common group of all Glycolipidso Occur in brain, spinal cords and other tissues.o Predominant in outer leaflet of biomembranes
  46. 46. GANGLIOSIDES (Ceramide + Oligosaccharide + Sialic acid) GM1 = Ganglioside with monosialic acid GD2 = Ganglioside with two sialic acid residues GT3 = Ganglioside with three sialic acid residuesSialic acid = N-Acetyl Neuraminic acid (NANA)
  47. 47. 1. Cerebrosides 2. Sulfatides Types ofGlycolipids 3. Globosides 4. Gangliosides
  48. 48. STEROIDSLipids containing Cyclo Pentano Perhydro Phenanthrene(CPPP) ring 18 12 17 11 16 13 C D 1 19 9 14 15 2 10 8 A B 3 7 5 4 6
  49. 49. STEROLSSteroids containing alcoholic group - SterolsPlant Sterols : Ergosterol, Stigmasterol, SitosterolAnimal Sterols : Cholesterol
  50. 50. CHOLESTEROLChemistry: Has Steroid Nucleus OH group at 3rd position Double bond between 5th & 6th carbons 8-Carbon containing side chain at 17th position. 17 3 5 6
  51. 51. CHOLESTEROLChemical Properties 1. Undergoes rapid oxidation to form cholestenones. 2. Hydroxyl group forms esters with acids to form Cholesterol Esters (cholesterol acetate,palmitate and propionates) 3. Presence of double bond gives hydrogenation reactions (similar to unsaturated fatty acids). 4. Colour reactions: LIEBERMANN BURCHARD, SALKOWSKY, ZAKS.
  52. 52. CHOLESTEROLBiomedical ImportanceStructural role – Biomembranes, LipoproteinsOccur in large amounts in brain and nerve tissues.Act as insulator against nerve impulses which discharge electric charges.Biomolecules synthesized from cholesterol Bile acids Vitamin D Steroid hormones : Androgens, Estrogens, Progesterone, Aldosterone etc
  53. 53. BILE ACIDS Cholesterol is eliminated from the body as bile acids through bile. Help in digestion & absorption of fats and fat soluble vitamins Synthesised in liver, stored in gall bladder and act in intestine
  54. 54. BILE ACIDS Primary Bile Acids Secondary Bile AcidsSynthesised from Cholesterol Synthesised from primaryin Hepatocytes Bile acids in IntestineEx: Ex:Cholic acid Deoxycholic acidChenodeoxycholic acid Lithocholic acid
  55. 55. EICOSANOIDES20 CARBON CONTAINING FATTY ACIDS GENERATED FROMARACHIDONIC ACID • Discovered in prostate gland secretions • Synthesized in all tissues • Acts as local hormones • Function in even low concentrations
  56. 56. EICOSANOIDES COX LOXProstanoides Leukotrienes LipoxinsProstaglandinsThromboxanesProstacyclins
  57. 57. Prostaglandin O OHProtanoic acid – Precursor moleculeCyclopentane ring substituted with hydroxyl / keto groupsBased on difference in these substituted groups, PGs classified as PG-A, PG-B, PG-C, PG-D, PG-E, PG-F, PG-HBased on number of double bonds, PGs have three series PG1 – One double bond PG2 – 2 double bonds PG2 - most common series PG3 – 3 double bonds
  58. 58. Functions of prostaglandin Smooth muscle contraction/relaxation  Vaso constriction  Broncho dilation (PGE2)  Uterine contraction (PGF2) Capillary permeability Inflammation and pain Platelet aggregation
  59. 59. ThromboxanesUnsaturated, substituted C-20 fatty acids with an oxanering.Occur in the cells of many tissues like blood platelets,lung, brain etc.
  60. 60. PGI2 Vs TXA2Prostacyclin (PGI2) Thromboxane (TXA2)Produced mainly from Produced mainly fromvascular endothelium plateletsSmooth muscle relaxation Smooth muscle contractionInhibits platelet aggregation Stimulates platelet aggregation
  61. 61. Leukotrienes, Lipoxins
  62. 62. Lipids having both hydrophobic and hydrophilic groupsEx: Phospholipids Cholesterol Glycolipids
  63. 63. Lipid Aggregates in Aqueous Compartment Micelle Formation
  64. 64. Bilayer Formation
  65. 65. Liposome FormationPrepared by sonication of amphipathic lipids
  66. 66. Liposomes Liposomes (microscopic spherical vesicles) when mixed with water under special condition, the phospholipids arrange themselves to form a bilayer membrane enclosing water-filled central core Impermeable to polar materials and helps maintain the composition of the enclosed aqueous fluid.
  67. 67. Uses of Liposomes To deliver drugs proteins enzymes genes
  68. 68. Drug release
  69. 69. Are spherical complexes made up of lipids andproteins .
  70. 70. STRUCTURE Inner Core Outer Wall Nonpolar lipids Amphipathic lipids & Proteins.TAG, Cholesterol esters Phospholipids, Cholesterol
  71. 71. Lipoproteins = lipids + proteins Apoproteins Al All Alll B48 B100 Cl Cll D E
  72. 72. Functions of Apoproteins: 1. Act as structural components of lipoproteins. 2. Recognize the cell membrane surface receptors,. 3. Activate enzymes involved in lipoprotein metabolism .
  73. 73. TYPES OF LIPOPROTEINS Based on density (lipid:protein ratio)1. Chylomicrons2 . Very Low Density Lipoproteins (VLDL)3 . Low Density Lipoproteins (LDL)4 . High Density Lipoproteins (HDL)
  74. 74. Ultracentrifugation Electrophoresis
  75. 75. Ultracentrifugation Chylomicrons VLDL IDL LDL HDL
  76. 76. Electrophoresis +ve +ve α -lipoprotein HDL VLDL Pre β IDL LDL β Lp Chylomicron -ve -ve
  77. 77. Lipoprotein Apo lipoprotein Functions (trnspt Chol.,)Chylomicron Apo AI, AI, B48, CI, CII, CIII, E Intestine to tissueVLDL B100, CI, CII, CIII, E Liver to tissueLDL B100 Liver to tissueIDL B100 Liver to tissueHDL Apo AI, AII, AIV, CI, CII, CIII, E Tissue to liver
  78. 78. RANCIDITY OF FATSFormation of unpleasant odour and taste in stored lipids iscalled as Rancidity.• Denotes the deterioration of lipids & becomes unsuitable for consumption• Occurs when exposed to air, moisture or bacteria• TGL with unsaturated fatty acids more susceptible for rancidity
  79. 79. Types of Rancidity1. Hydrolytic Rancidity: Partial hydrolysis of TGL by the bacterial enzymes 2. Oxidative Rancidity: Partial oxidation of fats leading to formation of peroxides & their corresponding aldehydes Prevented by adding Anti-oxidants
  80. 80. LIPID PEROXIDATION Free Radicals Lipids Lipid peroxides + Free Radicals O2Lipid peroxidation - generates of free radicals (ROO*,RO*,OH*)Free radicals : Have unpaired electrons in their outer orbits They oxidize & damage any biomoleculesPeroxidation : damages tissues in vivo,(free radicals) causes of cancer, Inflammatory diseases, atherosclerosis, and aging etc.
  81. 81. Three Stages of Peroxidation 1. Initiation2. Propagation3. Termination
  82. 82.  Substances which control and prevent free radicals.Types1. Preventive Antioxidants: Decrease the rate of chain initiation step. Ex: Catalase, Metal ion chelators such as EDTA2. Chain Breaking Antioxidants: Interfere with chain propagation step. Ex : Superoxide dismutase(SOD), Vitamin EUses  Protects biomembrane from the effect of free radicals  Added in fats for storage purpose  Protects the body from multiple diseases
  83. 83. Tests to check the purity of Simple Lipids1. Iodine Number2. Saponification Number3. Reichert Miesel Number4. Acid Number5. Acetyl number
  84. 84. Defined as the number of grams of iodine taken upby 100gms of fat.Index of degree of unsaturationIodine Number degree of unsaturation ‫ﻌ‬Uses: To detect the degree of unsaturation To detect adulteration
  85. 85. IODINE NUMBER Fats / Oils Iodine NoCoconut oil 7-10Butter 25-28Groundnut oil 85-100Sunflower oil 125-135
  86. 86. SAPONIFICATION NUMBERDefined as the number of milligrams (mgs) of potassiumHydroxide (KOH) required to saponify one gram of fat.Index of molecular weight / chain length fatty acids 1Saponification Number ‫ﻌ‬ molecular weight (or) chain lengthUses: To detect molecular weight / chain length fatty acids To detect adulteration
  87. 87. ACETYL NUMBERDefined as the Milligrams of KOH required to combinewith the acetic acid liberated by the saponification of1 gm of acetylated fat. Indicator of number of hydroxyl groups Castor oil has acetyl value of 146 to 150 indicating the presence of sufficient hydroxylated acids. Butter has an acetyl value of 1.9 to 8.6 ,indicating the presence of very small amounts of hydroxylated acids.
  88. 88. REICHERT-MEISSL NUMBERDefined as the millimeters of 0.1N alkali required toneutralize the volatile acids obtained from 5 gm of fat . Butter fat has a Reichert-Meissl number of 26-33 whereas the number for lard is 0.6.
  89. 89. ACID NUMBERDefined as the Milligrams of KOH required to neutralizethe free fatty acids present in 1gm of fat. It is of value in determining rancidity due to free fatty acids.