Lipid Structure Reza Meshkani, PhD Department of Biochemistry Faculty of Medicine Tehran University...

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Transcript of Lipid Structure Reza Meshkani, PhD Department of Biochemistry Faculty of Medicine Tehran University...

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  • Lipid Structure Reza Meshkani, PhD Department of Biochemistry Faculty of Medicine Tehran University of Medical Sciences
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  • Introduction 1.The role of Lipids 2.Main components and Properties of Lipids 3.Classification of lipids - Triglycerides -Phospholipids -Sterols -Ecosanoids -Isoprenoids 4-Lipid Digestion 5- Transport of lipids 6- Lipoprotein Metabolism
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  • Lipids Functions 1.Provide Energy (9 kcal/g). 2. Protects vital organs against shock. 3. Insulates body against temperature extremes. 4. Carrier of fat soluble vitamins A,D,E, and K. 5. Give flavor to foods. 6. Important components of membranes 7. Helps body use carbohydrates and protein efficiently
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  • Lipid Components Fatty acidsAlcohol Ester band=R1COOR2 Amid band=R1CONR2 Saturated Unsaturated Glycerol Phosphoglycerol Sterols Sphingosine Lipid Components
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  • long chain linear hydrocarbons carboxylic acids Usually have an even number of C atoms (usually 12 to 20) The carbons are numbered starting from the carboxylic C. They are amphiphilic; they have a polar end and rest of the molecule is nonpolar Fatty acids may be saturated (no double bonds) or unsaturated (one or more double bonds) All naturally occurring double bonds have a cis-configuration Longer chain and saturation increases melting point of FA Fatty Acids
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  • A ( A ) .
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  • Function of Fatty Acids 1. Fuel and energy metabolism free fatty acids and triglyceride 2. Membrane structure complex lipids 3. Cholesterol metabolism cholesteryl ester is the major form in which cholesterol is transported or stored 4. Metabolic regulators free fatty acids, eicosanoids, complex lipids
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  • 1. Short Chain fatty acids Less than 6 carbons (most in dairy products) Length of Fatty Acids 2. Medium Chain fatty acids 6-10 carbons 3. Long Chain fatty acids 12-22 carbons (most common in the diet)
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  • Nomenclature 1- Based on hydrocarbon molecule with the number and arrangement of carbon atoms ssaturated = anoic; octanoic acid (octa =8) unsaturated = enoic; octadecenoic acid (octa = 8 and deca = 10, thus 18) Palmitic (hexadecanoic);16:0 Palmitoleic acid: 9-hexadecenoic acid Stearic acid: Octadecanoic acid): 18:0 Oleic Acid (9,-octadecenoic);18:1; 9 Arachdonic acid ( 5,8,11,14-eicosatetraenoic acid)
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  • Nomenclature 2- Terminal methyl carbon (CH3) as n-carbon or -carbon The carbon atom adjacent to the carboxyl carbon (No.2) is known as the carbon 9 = indicates first or only double bond on the ninth carbon counting from the terminal methyl (omega) carbon (n)
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  • Nomenclature 3- unsaturated: where is/are double bond(s)?. 9 = double bond between carbon atoms 9 and 10 9,12 = double bonds between 9 and 10, 12 and 13
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  • Nomenclature 4-Classical name
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  • Fatty Acids Saturated Fatty acids No double bonds: 1. lauric acid (laurate) (12:0) 2. myristic acid (myristate) (14:0) 3. palmitic acid (palmitate) (16:0) 4. stearic acid (stearate) (18:0) Monounsaturated Fatty Acids One double bond 1. Oleic acid (oleate) (18:1cis) 2. Elaidic acid (elaidate) (18:1trans) Polyunsaturated Fatty Acids Two or more double bonds 1. Linoleic acid (linoleate) (18:2; 9,12) 6 2. Linolenic acid (linolenate) (18:3; 9,12,15) 3 3. Arachidonic acid (arachidonate) (20:4; 5,8,11,14) 6
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  • 3 and 6 Fatty acids Omega-3 -3 fatty acids (Linolenic) are found mainly in fish and fish products. -3 FAs inhibit formation of thromboxane A2 (an eicosanoid) required for platelet aggregation and clot formation. Thus, -3 FAs decrease the risk of heart disease Omega-6 Linoleic acid: Vegetable oils (corn, safflower, soybean, cottonseed, sesame, sunflower) Arachidonic acid: Meats (can be made from linoleic acid)
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  • ( ) .
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  • Palmitic acid, The most common saturated fatty acid found in animals and plants. Palmitic acid is the first fatty acid produced during Lipogenesis (fatty acid synthesis) Intake of palmitic acid increases risk of developing cardiovascular diseases.
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  • Arachidonic acid is present in the phospholipids involved in cellular signaling as a lipid second messenger
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  • Why are these essential? In most mammals, double bonds can be formed at the 4, 5, 6, and 9 positions, but never beyond 9, therefore any fatty acid that needs to add a double bond after 10 for example are essential Essential FFA functions: Needed for eicosanoid production Part of structural lipids of the cell and add structural integrity of mitochondrial membrane Necessary for fetal development, brain, and retina (vision) all saturated fatty acids are nonessential all monounsaturated fatty acids are nonessential
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  • Saponification Solubility Isomeration Melting temperature Halogenation Oxidation
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  • Alkali hydrolysis of fatty acids R-COOH + NaOH, KOH RCOONa+H2O
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  • Isomeration saturated fatty acids (zig zag pattern) unsaturated fatty acids 1.cis: acyl chains are on the same side of the double bond (nearly all naturally occurring fatty acids) 2. trans: acyl chains are on opposite sides of the bond present in certain foods Most arise due to partial hydrogenation (saturation) of polyunsaturated fatty acids of natural oils (margarine)
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  • Hydrogenation Hydrogenation: process of replacing some double bonds of polyunsaturated fats with hydrogen atoms. The process by which vegetable oil becomes margarine. When vegetable oils are hydrogenated, some double bonds undergo a change in configuration and are concerted to Trans Fatty Acids. The Cis configuration is typical of the fatty acid in natural foods. The Trans fatty acids (formed during hydrogenation) may raise LDL and lower HDL level.
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  • melting points of even-numbered carbon fatty acids increase with chain length and decrease according to unsaturation saturated, long-chain fatty acids are solid at body temperature (high melting point) polyunsaturated fatty acids are liquid at 0C (low melting point) The membrane lipids, which must be fluid at all environmental temperatures, are more unsaturated Question? Melting Temperature
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  • Peroxidation (auto-oxidation) of lipids is responsible for deterioration of foods and also damage of tissues which causes cancer, inflammatory disease, atherosclerosis, etc. The reaction is initiated by an existing free radical (X. ), by light or by metal. The deterioration effects cause by free radicals (ROO., RO., OH. ) produced during peroxide formation from fatty acids (unsaturated) Lipid peroxidation
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  • . .
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  • Lipid peroxidation Anti-oxidants: - BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene) are antioxidants used as food derivates -Vit E, C, Beta carotene, glutathion( ) -Catalase, superoxid dismutase, lipooxygenase Polyunsaturated fats spoil more easily than saturated fats. Rancidity: Flavor and odor of fat is affected, due to the oxidation of double bonds. To protect polyunsaturated fats from rancidity: 1. Refrigeration 3. Hydrogenation
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  • Alcohol GlycerolPhosphoglycerolMonohydric alcoholSterolAmine Alcohol (Sphingosine)
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  • Glycerol is the basis of Triglyceride Phosphoglycerol is basis of Phospholipids
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  • Sterols: Lipids containing multiple rings of carbon atoms. Are essential components of cell membranes and many hormones Are manufactured in our bodies and therefore are not essential components of our diet Sterols are basis of Cholesterol, Bile Acids, Steroid hormones and Vitamin D Sterol
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  • Sphingosine CH3-(CH2)12-CH=CH-CH-CH-CH2OH OH NH2 Fatty acid Sphingosine is basis of Sphingolipids
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  • TriglyceridesPhospholipidsSphingolipidsWaxesStroidsLipoproteinsEicosanoids Classification of Lipids
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  • Triglycerides In Triacylglycerol (TG) all 3 OH of glycerol are esterified by FAs. Monoacylglygerol and diacylglycerol have, respectively, 1 and 2 FAs Naturally occurring glycerol is L-glycerol. TG are the storage form of FA; most dietary fats are triglycerides Physiologically, TG are digested in the small intestine by the enzyme pancreatic lipase Monoacylglycerols are absorbed through the intestinal cells, re-converted to TG and assembled into lipoproteins
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  • 1. 2. 3. 4. 150 /
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  • Triglycerides Fatty acids can differ in Length of their carbon chain Short-, medium-, or long-chain Level of saturation Saturation refers to how many hydrogen atoms surround each carbon Shape The shape of a triglyceride is determined by the saturation of the carbon chains. Saturated fatty acids can pack tightly together an