Bài giảng Biochemistry 2/e - Chapter 8: Lipids

Chapter 8Lipidsto accompanyBiochemistry, 2/ebyReginald Garrett and Charles GrishamAll rights reserved. Requests for permission to make copies of any part of the work should be mailed to: Permissions Department, Harcourt Brace & Company, 6277 Sea Harbor Drive, Orlando, Florida 32887-6777 Outline8.1 Fatty Acids8.2 Triacylglycerols8.3 Glycerophospholipids8.4 Sphingolipids8.5 Waxes8.6 Terpenes8.7 SteroidsClasses of LipidsAll biological lipids are amphipathic Fatty acids Triacylglycerols Glycerophospholipids Sphingolipids Waxes Isoprene-based lipids (including steroids)8.1 Fatty acidsKnow the common names and structures for fatty acids up to 20 carbons long Saturated Lauric acid (12 C) Myristic acid (14 C) Palmitic acid (16 C) Stearic acid (18 C) Arachidic acid (20 C) Fatty acids - IIUnsaturated fatty acids Palmitoleic acid (16:1) Oleic acid (18:1) Linoleic acid (18:2) -Linolenic acid (18:3) -Linolenic acid (18:3) Arachidonic acid (20:4) Fatty acids - IIIStructural consequences of unsaturation Saturated chains pack tightly and form more rigid, organized aggregates (i.e., membranes) Unsaturated chains bend and pack in a less ordered way, with greater potential for motion 8.2 TriacylglycerolsAlso called triglycerides A major energy source for many organisms Why? Most reduced form of carbon in nature No solvation needed Efficient packing Triacylglycerols - IIOther advantages accrue to users of triacylglycerols Insulation Energy without nitrogen Metabolic water 8.3 GlycerophospholipidsGlycerophospholipids are phospholipids but not necessarily vice versa Know the names and structures in Figure 8.6 Understand the prochirality of glycerol Remember that, if phospholipid contains unsaturation, it is at the 2-position Ether GlycerophospholipidsAn ether instead of an acyl group at C-1 See Figure 8.8 Plasmalogens are ether glycerophospholipids in which the alkyl chain is unsaturated Ether GlycerophospholipidsPlatelet activating factor (PAF) is an ether glycerophospholipid PAF is a potent biochemical signal molecule Note the short (acetate) fatty acyl chain at the C-2 position in PAF 8.4 SphingolipidsBase structure is sphingosine Sphingosine is an 18-carbon amino alcohol Ceramides are amide linkages of fatty acids to the nitrogen of sphingosine Glycosphingolipids are ceramides with one or more sugars in beta-glycosidic linkage at the 1-hydroxyl group 8.4 SphingolipidsGlycosphingolipids with one sugar are cerebrosides Gangliosides - ceramides with 3 or more sugars, one of which is a sialic acid8.5 WaxesEsters of long-chain alcohols with long-chain fatty acids Highly insoluble Animal skin and fur are wax-coated Leaves of many plants Bird feathers 8.6 TerpenesBased on the isoprene structure Know nomenclature Understand linkage modes (Figure 8.16) See structures in Figure 8.17 All sterols (including cholesterol) are terpene-based molecules Steroid hormones are terpene-based8.7 SteroidsBased on a core structure consisting of three 6-membered rings and one 5-membered ring, all fused togetherCholesterol is the most common steroid in animals and precursor for all other steroids in animalsSteroid hormones serve many functions in animals - including salt balance, metabolic function and sexual function