LIPIDS PDF

‫‪LIPIDS‬‬ ‫أ‪.‬د‪.‬عادل محمد مليطان‬  LIPIDS A biological compound that is insoluble in water but soluble in an organic solvent(ether, benzene , acetone, chloroform). “lipid” is synonymous with“fat”, but...

‫‪LIPIDS‬‬ ‫أ‪.‬د‪.‬عادل محمد مليطان‬  LIPIDS A biological compound that is insoluble in water but soluble in an organic solvent(ether, benzene , acetone, chloroform). “lipid” is synonymous with“fat”, but also includes phospholipids, sterols, etc. chemical structure: glycerol + fatty acids (O-C=OR) Ester Bond  Functions lipids are concentrated sources of energy (9.45 kcal/g) more than double energy that gives the protein or carbohydrate 1) Provide the body with essential fatty acids that can not Made by the body and important for children's growth and mental development for them And also important for the skin 2) A source of phosphorus through phospholipids 3) Provide the body with fat-soluble vitamins (A,D,K,E) 4) Existence under the skin is an insulator from the effects of weather and also protects the internal organs such as the heart and kidney 5) Important for the production of Vitamin "D"  Lipid Classes simple: FA’s esterified with glycerol (Neutral Fats TG,FAT and OIL , Waxes) compound: same as simple,but with other compound s also attached A- phospholipids: fats containing phosphoric acid and nitrogen. B- glycolipids: FA’s compounded with CHO, but no N derived lipids: substances from the above derived by hydrolysis ‫ الستيرويدات‬: sterols: large molecular wt. alcohols found in nature and combined w/FA’s (e.g., cholesterol)  Fatty Acids Composed of a carboxylic acid “head group” and a long hydrocarbon“tail” – tail generally contains an even number of carbon atoms Hydrocarbon tail can be saturated or unsaturated – unsaturated hydrocarbon tails contain one or more double bonds Both common and systematic nomenclatures are widely used – eg. stearic acid or octadecanoic acid (1CH3, 16 CH2 + 1 CO2H) General structure of fatty acid, with the carboxylic acid “head group” shown in red  Saturated vs. Unsaturated Fatty Acids saturated: the SFA’s of a lipid have no double bonds between carbons in chain( CH3–(CH2)14–COOH (Palmitic Acid) polyunsaturated: more than one double bond in the chain :Mono-unsaturated (Oleic acid) CH3-(CH2)7-CH=CH-(CH2)7-COOH :Tetra-Unsaturated(Arachidonic acid) CH3-(CH2)4-CH=CH-CH2-CH=CH-CH2-CH=CH-CH2-CH=CH(CH2)3COOH most common polyunsaturated fats contain the polyunsa turated fatty acids (PUFAs) oleic, linoleic and linolenic acid Typical Saturated and Unsaturated Fatty Acids Sat. Fatty Acids Formula Melting Point (oC) Butyric C4H8O2 Liquid Palmitic C16H22O2 63 Stearic C18H36O2 70 Unsat. Fatty Acids Formula Melting Point (oC) Oleic C18H34O2 Liquid Linoleic C18H32O2 Liquid Linolenic C18H30O2 Liquid  Essential Fatty Acids Those needed by the body, but not synthesized within the body in adequate amounts. For humans, linoleic and linolenic acid are ess ential, but easily obtainable from plant and fish oils. Essential Fatty Acids ( )  Non essential Fatty Acids synthesized within the body in adequate amounts. Oleic acid CH3-(CH2)7-CH=CH-(CH2)7-COOH  Linoleic acid 18:2 (9,12) α-linolenic acid, 18:3(9,12,15) "Omega-6" –Omega “ -6" means the double bond is 6C from the terminal Ɛ Ɛ 18:3(9,12,15) a-Linolenic acid, Eicosapentaenoic acid ("EPA"), 20:5(5,8,11,14,17) "Omega-3" – found in marine animals Omega numbering Ɛ  Waxes Waxes are composed of a long-chain fatty acid bonded to a long-chain alcohol. They form protective coverings ((‫اغطيه وقائية‬for plants and anim als (plant surface (leaves), animal ears(skin,hair ). Esters of fatty acids and long chain alcohols. Water insoluble and not easily hydrolyzed Often found in protective coatings.  Waxes Triacontanylpalmitate is the main component of bee wax. Palmiticacid (C16:0) is esterified by a C30 chain, triacontanol(or melissylalcohol). Triacontanol is a fatty alcohol of the general formula C30H62O  Triacylglycerols(triglycerides) which are triesters of long chained fatty acids and glycerol. Fatty Acid + Glycerol = monoacylglycerol Fatty Acids + Glycerol = diacyl glycerol Fatty Acids + Glycerol = triacyl glycerol Simple Triglycerides Comprised with only one fatty acid on a glycerol backbone. Mixed Triglycerides Contain different fatty acids on the same glycerol backbone. Structure of a mixed triglycerol in which three different fatty acid residues are present.  Fats and Oils Triglycerides that are solid at room temperature are called FATS. Usually from animal sources. Contain a high degree of saturated fatty acids. Triglycerides that are liquid at room temperature are called OILS. Usually from plant and fish sources. Are liquids at room temperature. Contain more unsaturated fatty acids.  Simple lipids reactions 1.Esterification Glycerol and Fatty acids formC triglycerides. RCOOH + ROH = + -OR + H2O 2.Hydrolysis O important for fat and oil digestion. 3. Saponification the commercial production of the carboxylate salts of fatty acids in triglycerides (soaps). 4. Hydrogenation Double bonds of unsaturated fatty acids are hydrogen ated = to - used to make margarines from oils.  5.Oxidation oxidation of double bonds of fatty acids in fats and oils Compound Lipids  Steroids Steroids are non hydrolyzable lipids. All steroids con tain the following fused ring system: Cyclopentanoperhydrophenanthrene ‫سايكلوبنتانوبيرهيدروفينانثرين‬ ‫نواة الستيرويد‬  Cholesterol, an important constituent of cell membranes, has a rigid ring system and a short branched hydrocarbon tail. HO Cholesterol Cholesterol is largely hydrophobic. But it has one polar group, a hydroxyl, making it amphipathic( (water-loving, polar) and lipophilic (fat-loving) properties. PDB 1N83 cholesterol  HO Cholesterol Cholesterol inserts into bilayer membranes(is a thin polar membrane made of two layers of lipid molecules) with its hydroxyl group oriented toward the aqueous phase & its hydrophobic ring system adjacent(‫ )مجاور‬to fatty acid chains of phospholipids. The OH group of cholesterol forms hydrogen bonds with polar phospholipid head groups.  Glycerophospholipids Glycerophospholipids CH2OH (phosphoglycerides), are common constituents of cellular membranes. H C OH They have a glycerol backbone. CH2OH Hydroxyls at C1 & C2 are esterified glycerol to fatty acids. Formation of an ester: An ester forms when a hydroxyl reacts with a carboxylic acid, with loss of H2O. O O R'OH + HO-C-R" R'-O-C-R'' + H2O  Phosphatidate O O H2C O C R2 R1 C O CH O H2C O P O− O− phosphatidate In phosphatidate: ‫بحمض الفوسفاتيديت‬ fatty acids are esterified to hydroxyls on C1 & C2 the C3 hydroxyl is esterified to Pi.  O O H2C O C R2 R1 C O CH O H2C O P O O− H OH OH H OH OH H phosphatidyl- H H inositol H OH Phosphatidylinositol, with inositol as polar head group, is one glycerophospholipid. In addition to being a membrane lipid, phosphatidylinositol has roles in cell signaling(‫)بارز‬.  O O H2C O C R2 R1 C O CH O CH3 ‫مادة قاعدية‬ + H2C O P O CH2 CH2 N CH3 O− CH3 phosphatidylcholine *‫فوسفوتيدايل كول‬ Phosphatidylcholine, with choline as polar head group, is another glycerophospholipid. It is a common membrane lipid. Phosphatidylcholine  Each glycerophospholipid O includes a polar region: O H2C O C R2 glycerol, carbonyl O R1 C O CH O of fatty acids, Pi, & the H2C O P O X polar head group (X) non-polar hydrocarbon O− glycerophospholipid tails of fatty acids (R1, R2). polar "kink" due to double bond non-polar ‫السفينجومايل!‬ Double bonds in fatty acids usually O β have the cis configuration. γ α C Most naturally occurring fatty 4 3 1 O− 2 acids have an even number of carbon atoms. fatty acid with a cis-Δ9 double bond Some fatty acids and their common names: 14:0 myristic acid; 16:0 palmitic acid; 18:0 stearic acid; 18:1 cisD9 oleic acid 18:2 cisD9,12 linoleic acid 18:3 cisD9,12,15 a-linonenic acid 20:4 cisD5,8,11,14 arachidonic acid 20:5 cisD5,8,11,14,17 eicosapentaenoic acid (an omega- 3)  O β γ α C 4 3 1 O− 2 fatty acid with a cis-Δ9 double bond There is free rotation about C-C bonds in the fatty acid hydrocarbon, except where there is a double bond. Each cis double bond causes a kink in the chain. Rotation about other C-C bonds would permit a more linear structure than shown, but there would be a kink.