[医药卫生]4lipids.ppt

Lipids 1 WhatisaFat Afat orLipid ismadeupofamoleculeofglycerolinwhichoneormoreofitsthreeoriginalhydroxylgroupshavebeenreplacedbyfattyacidchains triglyceridesphospholipidssterols Triglycerides Thethreehydroxylgroupsoftheglycerolmoleculecaneachcombinewithalaity 外类的 acidmoleculeandtheresultingesteriscalledatriglyceride Phospholipids Phospholipidsaresimilartofatsinthattheyhaveastructurebasedonglycerolbutinsteadofthethreehydroxylgroupsbeingcombinedwithafattyacid onlytwoaresocombined thethirdbeingcombinedwithphosphatelinkedtocholine Lecithin 卵磷脂 isthebestknownexampleofaphospholipid Itissynthesizedbybothplantsandanimals andisfoundinfoodssuchaseggyolkandsoybeans Functionofphopholipids Lecithinisasourceofcholine acompoundrequiredforfattransportandsometimeslistedasoneofB complexvitamins Affectthesynthesisofneurotransmitters suchasserotonin 复合胺 acetylcholine dopamine 多巴胺 andnorepinephrine 去甲肾上腺素 inbrain Areimportantcomponentsofmembranestructure Sterols Sterolscanbesynthesizedbyplantsandanimals arecalledasphyto sterols ergosterol麦角固醇andsitosterol谷固醇 andcholesterolindividually Cholesterolisanessentialconstituentofthecellmembraneofeverycell Butifitisexcessive itwillcausevasculardiseases Phyto sterolsarethoughttodecreasetheabsorptionofcholesterol Cholesterol Ch Saturated nodoublebonds e g aceticacidCH3COOH vinegar lard UnsaturatedMonounsaturated onedoublebondPolyunsaturated twoormoredoublebonds 2 ThetypeofFattyAcids 1 Accordingasthereisornotdoublebonds SFA MUFA n 6PUFA n 3PUFA 棕榈油16 0PalmOil 油酸18 1n 9Oleicacid 亚油酸18 2n 6 亚麻酸18 3n 3 Shortchainfattyacids lessthan6carbonchain Mediumchainfattyacids 8 12carbonchain Longchainfattyacids morethan14carbonchain 2 ThetypeofFattyAcids 2 Accordingtolengthofcarbonchain 2 ThetypeofFattyAcids 3 Accordingtodoublebondconfiguration Thedistinctionthatisdrawnbetweencisandtransfattyacidsmayseemlikeanunnecessarycomplicationbutithassomerelevancewhenconsideringtherelationshipbetweenthetypesoffatweeatandourhealth 3 PhysicalPropertiesoffats 1 SaturatedfatsHavehighproportionofsaturatedfattyacidssuchasmyristic肉豆蔻的andpalmitic棕榈酸的 Usuallyaresolidatroomtemperature Usuallyarefoundinanimalfoods beef pork lamb milk cheese exceptionsarecoconutandpalmoil Arethoughttoincreasethelevelofcholesterolinblood 3 PhysicalPropertiesoffats 2 MonounsaturatedfatsArefoundinoliveoilandpeanutoil oleicisthemostcommonMUFA ArethoughttohaveaneutraleffectonbloodcholesterolPolyunsaturatedfatsHavehighproportionofpolyunsaturatedfattyacidssuchaslinoleic linolenicacid fromplants andarachidonicacids fromanimals Usuallyareliquidatroomtemperature Usuallycomefromplants soy corn safflower exceptionarefishArethoughttodecreasethecholerterollevelinblood 4 DescribingFattyAcids Fattyacidsaredescribedbytheratioofthenumberofcarbonatomsinthechaintothenumberofdoublebondsandthepositionofthedoublebondisthoughttohavesignificanceinhealthissues Linoleicacid 亚油酸 is18 2omega 6fattyacidi eithasan18carbonchain twodoublebondsandthedoublebondliesbetweenthesixthandseventhcarbonatoms Linolenicacid 亚麻酸 is18 3omega 3fattyacid Examplesof 3and 6polyunsaturatedfattyacids Table1 CommonPUFA Table2Thecommenfattyacids 5 FatsfunctionintheBody storefoodenergy whenmetabolizedfatsreleasemoreenergythananyotherfoodconstituent insulatethebodyandprotectbodyandorganssuchaskidneysfromdamage areessentialpartsofcellwallsandmembraneofcellandorgans arenecessaryfortheproductionofvarioushormonesandvitaminD areimportantfortheproductionofsterolswhicharefoundinallanimalsandplants However onlycholesterolisfoundinanimals areessentialtransportagentsforfatsolublevitaminsaroundthebodytissues 1 Structuralelementinmembranes Lipidcanbefoundinmanytissuesandcells forexample MembraneisakindoflipidlayerwhichconsistsofPhospholipids GlycosphingolipidsandCholesterol Andsterolsisindispensableinthesterolshormone sproductinhumanbody Lipidsareoneofthethreemainclassesoffood alongwithcarbohydratesandproteins Theyareresponsibleforstoringenergythatanimalsdonotimmediatelyneed Ifneeded theycanproduceenergybymetabolismatanytime 2 Storageformsofmetabolicfuel Somelipid solublevitamins suchasvitaminA vitaminD vitaminEandvitaminKarealsobelongtolipids Thefoodfatcanhelpthebodytoabsorbthem 3 Assistinabsorptionoflipid solublevitamins 4 Immunerecognition Inaddition lipidscannotonlyinsulateheatbutalsosupportandprotecttheviscera 内脏 insidethebody keepthemawayfromdamage 5 Foodsenseintensifier Lipidsstaylonginthestomachascomparedwithglucideandtheprotein Ittakes4to6hourstodigestsomefoodwhichcontain50gfat So peoplealwaysfeelfull Besides lipidscanamelioratethesenseandthecapabilityoffood Forexample deepfriedfoodhasaspecialscent 6 Essentialfattyacids Smallamountsoffatareessentialforhumannutrition Oneessentialfattyacid linoleicacid mustbesuppliedinthediet sincethebodycannotproduceenough Linolenicacidandarachidonicacidwereonceconsideredessential However wenowknowthatthebodycanconvertlinoleicacidtoarachidonicacidandlinolenicacidcanonlypartiallyreplacelinoleicacid n 6与n 3脂肪酸代谢途径 膳食 18 2n 6 18 3n 3亚麻酸 亚油酸 产能 生成TG 磷脂 胆固醇酯 18 3n 6 20 3n 6 20 4n 6 22 4n 6 24 4n 6 24 5n 6 22 5n 6 18 4n 3 SDA 20 4n 3 20 5n 3 EPA 22 5n 3 24 5n 3 24 6n 3 22 6n 3 DHA 产能 生成TG 磷脂 胆固醇酯 AA AA 花生四烯酸 SDA 硬脂四烯酸 EPA 二十碳五烯酸 DHA 二十二碳六烯酸 6脱饱和 延长 5脱饱和 延长 6脱饱和 部分 氧化 延长 7 FunctionofEssentialfattyacids Thesefattyacidsarenecessaryfortheproductionofprostaglandins 前列腺素 thromboxanes 凝血素 andseveralothercompounds Prostaglandinsandthromboxanesaffectnearlyeveryphysiologicalsysteminthebody Importantcompositionofphospholipids whicharepartofthestructureofallcellmembranes Affectthemetabolismofcholesterol LDL Ch HDL CharecarrierofCholesterol 8 Deficiencysymptomsofessentialfattyacids Deficiencysymptomsofessentialfattyacidsincludedecreasedgrowth dermatitis fattyliver impairedreproductionandimpairedwaterbalance Thereisevidenceomega 3fattyacids foundinfish areimportantinpreventionofheartdisease 9 DigestionandAbsorption Digestion mouth LinguallipaseSmallerparticlesBecomeliquid Digestion stomach Fatfloatsaboveotherfoodcomponent Digestion intestine BilefromgallbladderLipasefrompancreasBecomefreefattyacids glycerolandmonoacyglycerol Bileacidsarederivativesofcholesterolsynthesizedinthehepatocyte Bileacidsareamphipathic 两性分子的 Digestionoffats bileacids 1 Emulsificationoflipidaggregates Bileacidshavedetergentactiononparticlesofdietaryfatwhichcausesfatglobulestobreakdownorbeemulsifiedintominute microscopicdroplets Emulsificationisnotdigestionperse 本质上 butisofimportancebecauseitgreatlyincreasesthesurfaceareaoffat makingitavailablefordigestionbylipases whichcannotaccesstheinsideoflipiddroplets Solubilizationandtransportoflipidsinanaqueousenvironment Bileacidsarelipidcarriersandareabletosolubilizemanylipidsbyformingmicelles 胶束 胶态离子 aggregatesoflipidssuchasfattyacids cholesterolandmonoglycerides thatremainsuspendedinwater Bileacidsarealsocriticalfortransportandabsorptionofthefat solublevitamins Digestionoffats bileacids 2 10 LipidAbsorption Someglycerol short chainfattyacids andmedium chainfattyacidscanbeabsorbedintothebloodstream theportalvein bydiffusingtheintestinalcells Theyareattachedtoalbumintotheliver Monoglyceridesandlong chainfattyacidsmergeintomicelles sphericalshapedcomplexes微团 fortransportthroughthemicrovilli 微绒毛 ofintestinalcells Whenmicellesdiffuseintointestinalcells themonoglyceridesandlong chainfattyacidsarereassembledintotriglyceridesandcarriedawaybyjoinedtoproteinsandphospholipidsintocomplexsubstancescalledchylomicrons CM andverylow densitylipoprotein VLDL Thesearereleasedinthelymphsystemandtransportedtothevein wheretheygototheliver Duringdigestion thefatsareattachedtobilesalt whichmakesthemwatersoluble Astheyareabsorbed thebilesaltssplitoff absorption Largemoleculefatmergeintomicellesfortransportingthroughthemicrovilliofintestinalcells Smallmoleculefatcouldbeabsorbedintothebloodstreamdirectly 11 LipidTransport Fatareinsolubleinwater Thischaracteristicisimportantbecauseitmeansthattheymustbecombinedwithawater solublesubstance usuallyprotein aslipoproteins tobetransportedinthebloodandlymphsystems PlasmaLipoprotein 血浆脂蛋白 PlasmaLipoprotein LipidsinPlasma calledlipoproteinLipids 555mgTG 100mgPhospholipids PL 200mg Lecithin 卵磷脂 70 神经鞘磷脂20 Cephalin 脑磷脂 10 ChAndCE 200mg Ch 55 CE 145 FFA 55mg Classes CompositionandStructureofPlasmaLipoprotein Classes electrophoresis 电泳法 CM pro ultracentrifugation 超离心法 CM chylomicron VLDL verylowdensitylipoprotein LDL HDL 血浆脂蛋白的分类 ultracentrifugation 1 210 StructureofLipoprotein Chylomicrons largestandleastdenselipoproteintransportsdiet derivedlipids primarilytriglycerides fromtheintestinetothecellsofthebody VLDL VeryLowDensityLipoproteins madebythelivertotransportliver synthesizedlipids primarilytriglycerides tothecellsofthebodyasitlosestriglycerides theycollectcholesterolfromotherlipoproteinsandbecomeLDL LDL LowDensityLipoproteins composedmostlyofcholesterolcarriesanddepositscholesteroltotissuecells muscle fatstores mammaryglands heart etc thelivercancontroltheamountofLDLincirculation LDLisexcessive itimplicatestoincreasedangerofheartdisease HDL HighDensityLipoproteins Smallestlipoprotein isthemostprotein denselipoproteincarriescholesterolandphospohlipidsfromthecellsbacktotheliverforrecyclingordisposal HighHDLcandecreasethedangerofheartdisease FactorsthatimproveLDL HDLratios 1 weightcontrol 2 monosaturatedorpolyunsaturatedfattyacidsinplaceofsaturatedfat 3