lecture 17 - 17-1MCB 354Lecture 17Structure and Properties...

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Unformatted text preview: 17-1MCB 354Lecture 17Structure and Properties of LipidsLipid BilayersReading in Lehninger:Chapter 10, pp. 343-357Chapter 11, pp. 380-381Membranes and their componentsMembranes..1.= Organized assemblies of lipidsand proteins+ covalently associated carbohydrate2.Surround all cells (= plasma membrane)surround organelles in eukaryotes (nuclei, mitochondria, chloroplasts, ER, Golgi, vacuole)3.Provide a 2D scaffolding for certain enzymes, for proteins involved inenergy generation, for receptor proteins that detect extracellular signals4.Regulate composition of intracellular spaces by controlling flow of nutrients, ions,waste products in and out of the cell and its organelles5.Characteristic feature of membrane lipids: amphipathic:one end of moleculeis highly hydrophobic, the other, hydrophilic6.Three general types of membrane lipid:i) glycerophospholipidsii) sphingolipidsiii) sterols17-2Fatty acids1.Carboxylic acids with long hydrocarbon chains2.Chain can be fully saturated, or contain one ormore double bonds(a few have 3-C rings,-OH groups, or methyl group branches)3.Nomenclature: specifies chain length and# double bonds, separated by colon:eg. 16-C saturated palmitic acid = 16:018-C oleic acid (w. one double bond = 18:1)Position of double bond specified by superscript #sfollowing(e.g. 20-C FA with double bonds betweenC-9 & C-10 and between C-12 and C-13 = 20:2 (9,12)4.The most commonly occurring FA have even #sof carbons in unbranched chains (even #results from biosynthesis from C2 units)5.FA are rarely free in nature: usually ester- oramide-linked to other components of lipids(in vertebrates, free FA circulate in blood boundnon-covalently to a carrier protein, serum albumin)17-318:0Unsaturated fatty acids17-4Double bondintroducesrigid 30 bend18:3 (9,12,15)Generalizations:1.In monounsaturated FA, double bond is usually between C-9 and C-10 (9)2.Other double bonds of polyunsaturated FA usually 12 and 153.Double bonds in FA chains almost never conjugated (i.e. not -CH=CH-CH=CH-)4.Double bonds almost always have cisconfiguration18:1 (9)Physical properties of fatty acids-1...
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lecture 17 - 17-1MCB 354Lecture 17Structure and Properties...

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