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Lipids

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Chemistry of lipids
Chemistry of lipids
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Lipids

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Lipids are organic compounds formed mainly from alcohol and fatty acids combined together by ester
 Lipids are insoluble in water, but soluble in fat or organic solvents (ether, chloroform, benzene, acetone).
 Lipids include fats, oils, waxes and related compounds.
 They are widely distributed in nature both in plants and in animals.

Lipids are organic compounds formed mainly from alcohol and fatty acids combined together by ester
 Lipids are insoluble in water, but soluble in fat or organic solvents (ether, chloroform, benzene, acetone).
 Lipids include fats, oils, waxes and related compounds.
 They are widely distributed in nature both in plants and in animals.

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Lipids

  1. 1. DEPARTMENT OF VETERINARY BIOCHEMISTRY SUBMITTED BY ;- BHAGRAJ GODARA M.V.Sc 1st year RAJASTHAN UNIVERSITY OF VETERINARY AND ANIMAL SCIENCES,BIKANER LIPIDS SUBMITTED TO ;- DR ANIL MOOLCHANDANI ASSOCIATE PROFESSOR VETY. BIOCHEMISTRY
  2. 2. LIPID  Lipids are organic compounds formed mainly from alcohol and fatty acids combined together by ester  Lipids are insoluble in water, but soluble in fat or organic solvents (ether, chloroform, benzene, acetone).  Lipids include fats, oils, waxes and related compounds.  They are widely distributed in nature both in plants and in animals.
  3. 3. CONCEPT MAP
  4. 4. BIOLOGICAL IMPORTANCE OF LIPIDS : • They are more palatable and storable to unlimited amount compared to carbohydrates. • They have a high-energy value (25% of body needs) and they provide more energy per gram than carbohydrates and proteins but carbohydrates are the preferable source of energy. • Supply the essential fatty acids that cannot be synthesized by the body. • Supply the body with fat-soluble vitamins (a, d, e and k). • They are important constituents of the nervous system. • Tissue fat is an essential constituent of cell membrane and nervous system. It is mainly phospholipids in nature that are not affected by starvation.
  5. 5. Function of Lipids 1. They are rich source of energy 2. Protect and insulate internal organs 3. Other type of lipids are found in nerve fibers and in hormones , which acts as chemical messenger. 4. Provide polyunsaturated fatty acids. 5. A major function of lipids is to build the cell membranes that separate the internal contents of the cells from the surrounding aqueous environment.
  6. 6. Fatty alcohols • (Glycerol & sphingosine) •Glycerol:  A trihydric alcohol (i.E., Containing three OH groups) and has the popular name glycerin.  It is synthesized in the body from glucose.
  7. 7. It has the following properties: • Colorless viscous oily liquid with sweet taste. • On heating with sulfuric acid or khso4 (dehydration) it gives acrolein that has a badodor. • This reaction is used for detection of free glycerol or any compound containing glycerol. • It combines with three molecules of nitric acid to form trinitroglycerin (tnt) that is used as explosive and vasodilator. • 4-on esterification with fatty acids it gives: monoglyceride or monoacyl- glycerol: one fatty acid + glycerol. • Diglyceride or diacyl-glycerol: two fatty acids + glycerol. • Triglyceride or triacyl-glycerol: three fatty acids + glycerol. • it has a nutritive value by conversion into glucose and enters in structure of phospholipids.
  8. 8. Uses of Glycerol : • pharmaceutical and cosmetic preparations. • Reduces brain edema in cerebrovascular disease. • Nitroglycerin is used as vasodilator especially for the coronary arteries, thus it is used in treatment of angina pectoris. • explosives manufacturing. • treatment of glaucoma (increased intraocular pressure)due to its ability to dehydrate the tissue from its water content.
  9. 9. Sphingosine:  The alcohol(monohydric) present in sphingolipids.  Synthesized in the body from serine and palmitic acid.  It is not positive with acrolein test.
  10. 10. Fatty acids • It is the simplest type of lipid and are found as components in more complex lipids. • It contains a long carbon chain attached to carboxylic acid group at one end. • Although the carboxylic acid is hydrophilic, the long hydrophobic carbon chain makes long-chain fatty acids insoluble in water. • Fatty acids have even number of carbon atoms, usually between 10-20.
  11. 11. Example • Lauric Acid – a 12-carbon acid found in coconut oil.
  12. 12. Structure of fatty acids • A fatty acid consists of a hydrophobic hydrocarbon chain with a terminal carboxylgroup
  13. 13. Classification of fatty acidsClassification of fatty acids Fatty acids saturated unsaturated monounsaturated polyunsaturated
  14. 14. Fatty acids • Saturated Fatty Acids such as lauric acid contain only single bonds between carbons. • Monounsaturated Fatty Acids have one double bond in the carbon chain. • Polyunsaturated Fatty Acids have two or more double bonds.  Appear to raise the level of LDL(“bad”) cholesterol in the bloodstream  Food sources: meat, poultry skin, whole- milk dairy products, and the tropicaloils- coconut oil, palm oil, and palm kernel oil.
  15. 15. Polyunsaturated FattyAcids  Fats that seem to lowertotal cholesterol levels.  Food sources: many vegetable oils, such as corn oil, soybean oil and safflower oil.
  16. 16. Physical Properties of Saturated Fatty Acids • Saturated fatty acids have:  Molecules that fit closely together in a regular pattern  Strong attractions (dispersion forces) between fatty acid chains  High melting points that makes them solids at roomtemperature.
  17. 17. Classification of Lipids •Simple lipids ( fats & waxes ) •Complex (compound or conjugated lipids ) •Derived lipids •Lipid - associating substances
  18. 18. Simple lipids • A - Neutral Fats and oils (Triglycerides) • Definition:  Neutral- uncharged due to absence of ionizable groups in it.  most abundant lipids in nature.  constitute about 98% of the lipids of adipose tissue, 30% of plasma or liver lipids, less than 10% of erythrocyte lipids.  They are esters of glycerol with various fatty acids. • Since the 3 hydroxyl groups of glycerol are esterified, the neutral fats are also called “Triglycerides”.
  19. 19. Waxes, Fats, and Oils
  20. 20. Waxes, Fats, and Oils • A wax is an ester of unsaturated fatty acid and long- chain alcohol, each containing from 14-30 carbon atoms. • Bees wax obtained from honey combs and carnauba wax obtained from palm trees are used to give a protective coating to furniture, car and floors. • Jojoba wax is used in making candles and cosmetics such as lipstick. • Lanolin, a mixture of waxes obtained from wool, is used in hand and facial lotions to aid retention of water, which softens the skin.
  21. 21. Some Typical Waxes
  22. 22. Fats and Oils: Triacylglycerols • In the body, fatty acids are stored as fats and oils known as triacylglycerols. • These substances, also called triglycerides, are triesters of glycerol and fatty acids.
  23. 23. Triacylglycerols • A triacylglycerol is produced by esterfication, a reaction in which the hydroxylgroups of glycerol form ester bonds with carboxyl groups of fatty acids.
  24. 24. Triacylglycerols • A triacylglycerol are the major form of energy storage for animals. • Animals that hibernate eat large quantities of plants,seeds and nuts that contain large amount of fats and oils. • They gain as much 14 Kg a week. As the external temperature drops, the animal goes into hibernation. The body temperature drops to nearly freezing and there is a dramatic reduction in cellular activity, respiration and heart rate. • Animals who live in extremely cold climates will hibernate for 4-7 months.
  25. 25. Triacylglycerols • However, most fats and oils are mixed triacyglycerols that contain two or three different fatty acids. • For example a mix tricylglycerol might be made from lauric acid,myristic acid and palmitic acid.
  26. 26. Melting Points of Fats and Oils. • A fat is a triacylglycerol that is solid at room temperature, such as fats in meat, whole milk, butter and cheese. Most fats come from animal sources. • An oil is a triacylglycerol that is liquid at room temperature. The most commonly used oils come from plant sources. Olive oil and peanut oil are monounsaturated because they contain large amounts of oleic acid. • Oils from corn,cotton seed, safflower and sunflower are polyunsaturated because they contain large amounts of fatty acids with two or more double bonds.
  27. 27. Diagram of Triacylglycerol with Unsaturated FattyAcids Unsaturated fatty acid chains with kinks cannot pack closely.
  28. 28. Melting Points of Fats and Oils. • Saturated fatty acids have higher melting points than unsaturated fatty acids because they pack together more tightly. • Vegetable oils have low melting points because they have a higher percentage of unsaturated fatty acids than do animal fats.
  29. 29. Chemical Properties of Triacylglycerols • The chemical reactions of triacylglycerols are similar to those of alkenes and esters. • In hydrogenation, double bonds in unsaturated fatty acids react with H2 in the presence of a Ni or Pt catalyst. • In hydrolysis, ester bonds are split by water in the presence of an acid, a base, or an enzyme.
  30. 30. 1.Hydrogenation of Oils • The hydrogenation of oils • adds hydrogen (H2) to the carbon atoms of double bonds. • converts double bonds to single bonds. • increases the melting point. • produces solids such as margarine and shortening.
  31. 31. Hydrogenation (CH2)5CH CH(CH2)7CH3 CH(CH2)7CH3(CH2)5CH O C (CH2)5CHCH(CH2)7CH3 O C O C OCH2 CH2 O CH O glyceryl tripalmitoleate (tripalmitolean) 2 14 3 O C (CH ) CH O 2 14 3C (CH ) CH O CH2 O C (CH2)14CH3 CH O2 CH O+ 3H2 Ni glyceryl tripalmitate (tripalmitin)
  32. 32. Olestra a Fat Substitute Olestra is • used in foods as an artificial fat. • sucrose linked by ester bonds to several long- chain fatty chains. • not broken down in the intestinal tract.
  33. 33. 2.Hydrolysis CH O CH2 CH OH CH2 OH OHCH2 O HO C (CH2)14CH3 H2O In hydrolysis, • triacylglycerols split into glycerol and three fatty acids. • an acid or enzyme catalyst is required. O O C (CH2)14CH3 O C (CH2)14CH3 O CH2 O C (CH2)14CH3 H+
  34. 34. 3.Saponification and Soap Saponification • is the reaction of a fat with a strong base. • splits triacylglycerols into glycerol and the salts of fatty acids. • is the process of forming “soaps” (salts of fatty acids). • with KOH gives softer soaps.
  35. 35. Saponification O C (CH2)14CH3 O CH O C (CH2)14CH3 CH2O O C (CH2)14CH3 CH2O + 3NaOH CH OH CH2 OH CH OH2 Na+ -O O C (CH2)14CH3+ Glyceryl tripalmitate Glycerol 3 sodium palmitate
  36. 36. (CH2)7 COOHCH3 (CH2)4 CH CH CH2 CH CH Linoleic acid 2 I2 CH CH (CH2)7 COOHCH CH CH2CH3 (CH2)4 I I I I Stearate-tetra-iodinate  Neutral fats containing unsaturated fatty acids have the ability of adding halogens (e.g., hydrogen or hydrogenation and iodine or iodination) at the double bonds.  very important property to determine the degree of unsaturation of the fat or oil that determines its biological value 4.Halogenation
  37. 37. 5.Oxidation (Rancidity)  This toxic reaction of triglycerides leads to unpleasant odour or taste of oils and fats developing after oxidation by oxygen of air, bacteria, or moisture.  Also this is the base of the drying oils after exposure to atmospheric oxygen.Example is linseed oil, which is used in paints and varnishes manufacturing = RANCID Definition:  physico-chemical change  development of unpleasant odor or taste or abnormal color particularly on aging  exposure to atmospheric oxygen, light, moisture, bacterial or fungal contamination and/or heat.  Saturated fats resist rancidity more thanunsaturated fats that have unsaturated double bonds.
  38. 38. Types and causes of rancidity 1. Hydrolytic rancidity 2. Oxidative rancidity 3. Ketonic rancidity 1-Hydrolytic rancidity: • from slight hydrolysis of the fat by lipase bacterial contamination leading to the liberation of free fatty acids and glycerol at high temp and moisture. • Volatile short-chain fatty acids have unpleasant odor.
  39. 39. 2-Oxidative Rancidity:  oxidation of fat or oil  by exposure to oxygen, light and/or heat producing peroxide derivatives  e.g., peroxides, aldehydes, ketones and dicarboxylic acids that are toxic and have bad odor.  due to oxidative addition of oxygen at the unsaturated double bond of unsaturated fatty acid of oils. 3-Ketonic Rancidity:  due to the contamination with certain fungi such as Aspergillus niger on fats such as coconut oil  Ketones, fatty aldehydes, short chain fatty acids and fatty alcohols are formed.  Moisture accelerates ketonic rancidity.
  40. 40. 1-Iodine number (or value):  Definition: It is the number of grams of iodine absorbed by 100 grams of fat or oil.  Uses: It is a measure for the degree of unsaturation of the fat, as a natural property for it.  Unsaturated fatty acids absorb iodine at their double bonds, therefore, as the degree of unsaturation increases iodine number and hence biological value of the fat increase.  It is used for identification of the type of fat, detection of adulteration and determining the biological value of fat.
  41. 41. 2-Saponification number (or value):  Definition: It is the number of milligrams of KOH required to completely saponify one gram of fat.  Uses:  Since each carboxyl group of a fatty acid reacts with one mole of KOH during saponification, therefore, the amount of alkali needed to saponify certain weight of fat depends upon the number of fatty acids present per weight.  Thus, fats containing short-chain acids will have more carboxyl groups per gram than long chain fatty acids and consume more alkali, i.e., will have higher saponification number.
  42. 42. 3-Acids Number (or value):  Definition: It is the number of milligrams of KOH required to neutralize the free fatty acids present in one gram of fat.  Uses: It is used for detection of hydrolytic rancidity because it measures the amount of free fatty acids present.
  43. 43. 4-Reichert- Meissl Number (or value):  Definition: It is the number of milliliters of 0.1 NKOH required to neutralize the water-soluble fatty acids distilled from 5 grams of fat. Short-chain fatty acid (less than 10 carbons) is distillated by steam.  Uses: This studies the natural composition of the fat and is used for detection of fat adulteration.  Butter that has high percentage of short-chain fatty acids has highest Reichert-Meissl number compared to margarine.
  44. 44. 5-Acetyl Number (or value):  Definition: It is number of milligrams of KOH needed to neutralize the acetic acid liberated from hydrolysis of 1 gram of acetylated fat (hydroxy fat reacted with acetic anhydride).  Uses: The natural or rancid fat that contains fatty acids with free hydroxyl groups are converted into acetylated fat by reaction with acetic anhydride.  Thus, acetyl number is a measure of number of hydroxyl groups present.  It is used for studying the natural properties of the fat and to detect adulteration and rancidity.
  45. 45. B-Waxes  Definition: Waxes are solid simple lipids containing a monohydric alcohol (with a higher molecular weight than glycerol) esterified to long-chain fatty acids. Examples of these alcohols are palmitoyl alcohol, cholesterol, vitamin A or D.  Properties of waxes: Waxes are insoluble in water, but soluble in fat solvents and are negative for acrolein test.  Waxes are not easily hydrolyzed as the fats and are indigestible by lipases and are very resistant to rancidity.  Thus they are of no nutritional value.
  46. 46. Type of Waxes:  - Waxes are widely distributed in nature such as the secretion of certain insects as bees-wax, protective coatings of the skins and furs of animals and leaves and fruits of plants. They are classified into true- waxes and wax-like compounds as follows: A-True waxes: include:  Bees-wax is secreted by the honeybees that use it to form the combs. It is a mixture of waxes with the chief constituent is mericyl palmitate.
  47. 47. Waxes Neutral lipids 1.Digestibility: 2-Type of alcohol: Indigestible (not Digestible (hydrolyzed by lipase). hydrolyzed by lipase). Long-chain monohydric Glycerol (trihydric) + 3 fatty acids alcohol + one fatty acid. 3-Type of fatty acids: 4-Acrolein test: 5-Rancidability: 6-Nature at room temperature. Fatty acid mainly palmitic Long and short chain fatty acids. or stearic acid. Negative. Positive. Never get rancid. Rancidible. Hard solid. Soft solid or liquid. 7-Saponification Nonsaponifiable. Saponifiable. 8-Nutritive value: No nutritive value. Nutritive. 9-Example: Bee & carnuba waxes. Butter and vegetable oils. Differences between neutral lipids and waxes:
  48. 48. 2-Compound Lipids They are lipids that contain additional substances, e.g., sulfur, phosphorus, amino group, carbohydrate, or proteins beside fatty acid and alcohol. Compound or conjugated lipids are classified into the following types according to the nature of the additional group: Phospholipids Glycolipids. Lipoproteins Sulfolipids and amino lipids.
  49. 49. Phospholipids • Definition: Phospholipids or phosphatides are compound lipids, which contain phosphoric acid group in their structure. • Importance: • They are present in large amounts in the liver and brain as well as blood.Every animal and plant cell containsphospholipids. The membranes bounding cells and subcellular organelles are composed mainly of phospholipids. Thus, the transfer of substances through these membranes is controlled by properties of phospholipids. • They are important components of the lipoprotein coat essential for secretion and transport of plasma lipoprotein complexes. Thus, they are lipotropic agents that prevent fatty liver. • Myelin sheath of nerves is rich withphospholipids.
  50. 50. Glycerophospholipids Glycerol Fatty acid Fatty acid PO4 Amino alcohol
  51. 51. Structure: phospholipids are composed of: Fatty acids (a saturated and an unsaturated fatty acid). Nitrogenous base (choline, serine, threonine, or ethanolamine). Phosphoric acid. Fatty alcohols (glycerol, inositol or sphingosine). Sources: They are found in all cells (plant and animal), milk and egg- yolk in the form of lecithins
  52. 52. Classification of Phospholipids • Are classified into 2 groups according to the type of the alcohol present into two types: • A-Glycerophospholipids: They are regarded as derivatives of phosphatidic acids that are the simplest type of phospholipids and include: • Phosphatidic acids. • Lecithins • Cephalins. • Plasmalogens. • Inositides. • Cardiolipin. • B-Sphingophospholipids: They contain sphingosine as an alcohol and are named Sphingomyelins.
  53. 53. A-Glycerophospholipids 1.Phosphatidic acids: They are metabolic intermediates in synthesis of triglycerides and glycerophospholipids in the body and may have function as a second messenger. They exist in two forms according to the position of the phosphate
  54. 54. 2-Lecithins:  Definition : Lecithins are glycerophospholipids that contain choline as a base beside phosphatidic acid. They exist in 2 forms  - and  - lecithins.  Lecithins are a common cell constituent obtained from brain ( - type), egg yolk ( - type), or liver (both types).  Lecithins are important in the metabolism of fat by the liver.  Structure: Glycerol is connected at C2 or C3 with a polyunsaturated fatty acid, at C1 with a saturated fatty acid, at C3 or C2 by phosphate to which the choline base is connected. The common fatty acids in lecithins are stearic, palmitic, oleic, linoleic, linolenic, clupandonic or arachidonic acids.
  55. 55. Lysolecithin • causes hemolysis of RBCs. This partially explains toxic effect of snake venom,. The venom contains lecithinase, which hydrolyzes the polyunsaturated fatty converting lecithin into lysolecithin. Lysolecithins are intermediates in metabolism of phospholipids.
  56. 56. Lung surfactant • Is a complex of dipalmitoyl-lecithin, sphingomyelin and a group of apoproteins called apoprotein A, B, C, and D. • It is produced by type II alveolar cells and • is anchored to the alveolar surface of type II and I cells. • It lowers alveolar surface tension and improves gas exchange besides activating macrophages to kill pathogens. • In premature babies, this surfactant is deficient and they suffer from respiratory distress syndrome. • Glucocorticoids increase the synthesis of the surfactant complex and promote differentiation of lung cells.
  57. 57. 3-Cephalins (or Kephalins):  Definition:  They are phosphatidyl- ethanolamine or serine. Cephalins occur in association with lecithins in tissues and are isolated from the brain (Kephale = head).  Structure: Cephalins resemble lecithins in structure except that choline is replaced by ethanolamine, serine or threonine amino acids. • Certain cephalins are constituents of the complex mixture of phospholipids, cholesterol and fat that constitute the lipid component of the lipoprotein “thromboplastin” which accelerates the clotting of blood by activation of prothrombin to thrombin in presence of calcium ions.
  58. 58. 4-Plasmalogens:  Definition: Plasmalogens are found in the cell membrane phospholipids fraction of brain and muscle (10% of it is plasmalogens), liver, semen and eggs.  Structure: Plasmalogens resemble lecithins and cephalins in structure but differ in the presence of , - unsaturated fatty alcohol rather than a fatty acid at C1 of the glycerol connected by ether bond. • At C2 there is an unsaturated long-chain fatty acid, however, it may be a very short-chain fatty acid
  59. 59. 5-Inositides: They are phosphatidyl inositol.  Structure: They are similar to lecithins or cephalins but they have the cyclic sugar alcohol, inositol as the base. They are formed of glycerol, one saturated fatty acid, one unsaturated fatty acid, phosphoric acid and inositol  Source: Brain tissues.  Function: Phosphatidyl inositol is a major component of cell membrane phospholipids particularly at the inner leaflet of it. • They play a major role as second messengers during signal transduction for certain hormone..  On hydrolysis by phospholipase C, phosphatidyl-inositol-4,5-diphosphate produces diacyl-glycerol and inositol- triphosphate both act to liberate calcium from its intracellular stores to mediate the hormone effects.
  60. 60. 6-Cardiolipins:  Definition: They are diphosphatidyl- glycerol. They are found in the inner membrane of mitochondria initially isolated from heart muscle (cardio). It is formed of 3 molecules of glycerol, 4 fatty acids and 2 phosphate groups.  Function: Used in serological diagnosis of autoimmunity diseases.
  61. 61. B-Sphingophospholipids • 1-Sphingomyelins  Definition: Sphingomyelins are found in large amounts in brain and nerves and in smaller amounts in lung, spleen, kidney, liver and blood.  Structure: Sphingomyelins differ from lecithins and cephalins in that they contain sphingosine as the alcohol instead of glycerol, they contain two nitrogenous bases: sphingosine itself and choline.  Thus, sphingomyelins contain sphingosine base, one long-chain fatty acid, choline and phosphoric acid.  To the amino group of sphingosine the fatty acid is attached by an amide linkage.
  62. 62. Ceramide  Ceramide This part of sphingomyelin in which the amino group of sphingosine is attached to the fatty acid by an amide linkage.  Ceramides have been found in the free state in the spleen, liver and red cells.
  63. 63. B-Glycolipids • Definition: They are lipids that contain carbohydrate residues with sphingosine as the alcohol and a very long-chain fatty acid (24 carbon series). • They are present in cerebral tissue, therefore are called cerebrosides • Classification: According to the number and nature of the carbohydrate residue(s) present in the glycolipids the following are • Cerebrosides. They have one galactose molecule (galactosides). • Sulfatides. They are cerebrosides with sulfate on the sugar (sulfated cerebrosides). • Gangliosides. They have several sugar and sugaramine residues.
  64. 64. 1-Cerebrosides: • Occurrence: They occur in myelin sheath of nerves and white matter of the brain tissues and cellular membranes.They are important for nerve conductance. • Structure: They contain sugar, usually  -galactoseand may be glucose or lactose, sphingosine and fatty acid, but no phosphoric acid.
  65. 65. • Types: According to the type of fattyacid and carbohydrate present, there are 4 different types of cerebrosides isolated from the white matter of cerebrum and in myelin sheaths of nerves. Rabbit cerebrosides contain stearic acid. • Kerasin contains lignoceric acid (24carbons) and galactose. • Cerebron (Phrenosin) contains cerebronic acid (2-hydroxylignoceric acid) and galactose. • Nervon contains nervonic acid(unsaturated lignoceric acid at C15) and galactose. • Oxynervon contains oxynervonic acid (2-hydroxynervonic acid) and galactose.
  66. 66. 2-Sulfatides: • They are sulfate esters of kerasin or phrenosin in which the sulfate group is usually attached to the –OH group of C3 or C6 of galactose. Sulfatides are usually present in the brain, liver, muscles and testes.
  67. 67. 3-Gangliosides: • They are more complex glycolipids that occur in the gray matter of the brain, ganglion cells, and RBCs. They transfer biogenic amines across the cell membrane and act as a cell membrane receptor. • Gangliosides contain sialic acid (N-acetylneuraminic acid), ceramide (sphingosine + fatty acid of 18-24 carbon atom length), 3 molecules of hexoses (1 glucose + 2 galactose) and hexosamine.
  68. 68. C-Lipoproteins • Definition: Lipoproteins are lipids combined with proteins in the tissues. The lipid component is phospholipid, cholesterol or triglycerides. The holding bonds are secondary bonds. • They include: Structural lipoproteins: These are widely distributed in tissues being present in cellular and subcellular membranes. In lung tissues acting as a surfactant in a complex of a protein and lecithin. In the eye, rhodopsin of rods is a lipoprotein complex. • Transport lipoproteins: • These are the forms present in blood plasma. They are composed of a protein called apolipoprotein and different types of lipids. (Cholesterol, cholesterol esters, phospholipids and triglycerides). As the • lipid content increases, the density of plasma lipoproteins decreases
  69. 69. Plasma lipoproteins can be separated by two methods • Ultra-centrifugation: Using the rate of floatation in sodium chloride solution leading to their sequential separation into chylomicrons, very low density lipoproteins (VLDL or pre-  -lipoproteins), low density lipoproteins (LDL or  - lipoproteins), high density lipoproteins (HDL or  -lipoproteins) and albumin-free fatty acids complex. • Electrophoresis: is the migration of charged particles in an electric field either to the anode or to the cathode.
  70. 70. • a) Chylomicrons: They have the largest diameter and the least density. They contain 1-2% protein only and 98-99% fat. The main • lipid fraction is triglycerides absorbed from the intestine and they contain small amounts of the absorbed cholesterol and phospholipids. b)Very low-density lipoproteins (VLDL) or pre-  -lipoproteins: Their diameter is smaller than chylomicrons. They contain about 7-10% protein and 90-93% lipid. The lipid content is mainly triglycerides formed in the liver. They contain phospholipid and cholesterol more than chylomicrons. c)Low-density lipoproteins (LDL) or  - lipoproteins: They contain 10-20% proteins in the form of apolipoprotein B. Their lipid content varies from 80-90%. They contain about 60% of total blood cholesterol and 40% of total blood phospholipids. As their percentage increases, the liability to atherosclerosis increases.
  71. 71. d)High-density lipoproteins (HDL) or  - Lipoproteins: They contain 35-55% proteins in the form of apolipoprotein A. They contain 45- 65% lipids formed of cholesterol (40% of total blood content) and phospholipids (60% of total blood content). They act as cholesterol scavengers, as their percentage increases, the liability to atherosclerosis decreases. They are higher in females than in males. Due to their high protein content they possess the highest density. e)Albumin-free fatty acids complex: It is a proteolipid complex with 99% protein content associated with long-chain free fatty acids for transporting them.
  72. 72. • Steroids: Cholesterol and Steroid Hormones C H 3 C H 3 C H 3 C H 3 H O C H 3
  73. 73. Steroid Nucleus A steroid nucleus consists of • 3 cyclohexane rings. • 1 cyclopentane ring. • no fatty acids. steroid nucleus
  74. 74. Cholesterol in the Body Cholesterol • is obtained from meats, milk, and eggs. • is synthesized in the liver. • is needed for cell membranes, brain and nerve tissue, steroid hormones, and vitamin D. • clogs arteries when high levels form plaque. A normal, open artery. An artery clogged by cholesterol plaque
  75. 75. Lipoproteins Lipoproteins • combine lipids with proteins and phospholipids. • are soluble in water because the surface consists of polar lipids.
  76. 76. Types of Lipoproteins Lipoproteins • differ in density, composition, and function. • include low-density lipoproteins (LDLs) and high- density lipoproteins (HDLs).
  77. 77. Steroid Hormones Steroid hormones are • chemical messengers in cells. • sex hormones. - androgens in males (testosterone) - estrogens in females (estradiol) • Adrenocortical hormones from adrenal glands. - mineralocorticoids (electrolyte balance) - glucocorticoids (regulate glucose level)
  78. 78. Steroid Hormones Steroid hormones • are produced from cholesterol. • include sex hormones such as androgens (testosterone) in males and estrogens (estradiol) in females.
  79. 79. Anabolic Steroids Anabolic steroids • are derivatives of testosterone. • are used illegally to increase muscle mass. • have side effects including fluid retention, hair growth, sleep disturbance, and liver damage.
  80. 80. Adrenal Corticosteroids Steroid hormones called adrenal corticosteroids • are produced by the adrenal glands located on the top of each kidney. • include aldosterone, which regulates electrolytes and water balance by the kidneys. • include cortisone, a glucocorticoid, which increases blood glucose level and stimulates the synthesis of glycogen in the liver.
  81. 81. Cell Membranes
  82. 82. Cell Membranes Cell membranes • separate cellular contents from the external environment. • consist of a lipid bilayer made of two rows of phospholipids. • have an inner portion made of the nonpolar tails of phospholipids with the polar heads at the outer and inner surfaces.
  83. 83. Fluid Mosaic Model of Cell Membranes The lipid bilayer • contains proteins, carbohydrates, and cholesterol. • has unsaturated fatty acids that make cell membranes fluid-like rather than rigid. • has proteins and carbohydrates on the surface that communicate with hormones and neurotransmitters.
  84. 84. Fluid Mosaic Model of Cell Membranes
  85. 85. Transport Through Cell Membranes • The transport of substances through cell membranes involves •simple diffusion (passive transport), which moves particles from a higher to a lower concentration. •facilitated transport, which uses protein channels to increase the rate of diffusion. •active transport, which moves ions against a concentration gradient.
  86. 86. Transport Pathways Through Cell Membranes
  87. 87. THANKS

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