第五章 脂类 Lipids2013.ppt

ImportantConceptsaboutLipids有关脂类的重要概念 Lipidsarethemostconcentratedsourceofdietaryenergy onaverage2 25timetheenergyinCHOorproteins脂类是饲粮能量含量最高的物质 平均是碳水化合物和蛋白质的2 25倍 Whenfeedisplentiful thebodyconvertsdietaryCHOandproteinstobodyfat thisfatisbrokendowntoprovideenergywhenfeedisscarce 当饲粮充足时 机体转化饲粮中碳水化合物和蛋白质生成体脂 当饲粮缺乏时这部分体脂降解提供能量 ImportantConceptsaboutLipids有关脂类的重要概念 Thevalueofafatoroilisdependentonitsfattyacidcontent脂肪或油脂的价值依据其脂肪酸的含量Thechemicalstructureoffattyacidsallowsthemtobepartofcellmembranes becomerancidandformsoaps 脂肪酸的化学结构允许他们成为细胞膜 形成和皂类 Twofattyacidsaredietaryessentials butneedsareeasytomeet两种脂肪酸是饲粮中必需 但很容易得到满足 LIPIDS脂类 Relativelyinsolubleinwater相对不溶于水Solubleinnonpolarsolventssuchasether溶于非极性溶剂 如乙醚Capableofbeingusedbylivingorganisms有机生物中应用 CRUDEFAT粗脂肪 ThetotallipidcontentoffeedstuffsismostcommonlydeterminedbytheCrudeFatprocedure 所有饲料原料中脂类含量多数通常通过粗脂肪程序测定Crudefatisallofthematerialinafeedstuffsolubleinether 粗脂肪在乙醚是全部溶解的 Crudefatissometimescalled etherextract 粗脂肪有时被称为乙醚浸提物 ClassificationofLipids脂类的分类 A Simplelipids estersoffattyacidsandalcohols脂肪酸的酯类和醇类Fatsandoils estersoffattyacidswithglycerol triglycerides 带甘油脂肪酸酯类 如甘油三酯 About95 ofthelipidsintissueandfeedstuffsarefatsoroils 在组织和饲料原料中 95 的脂类是脂肪和油脂 2 Waxes腊 estersoffattyacidswithhighmolecularweightalcohols高分子量的脂肪酸的酯类Example beeswax waxesinleaves fruits ClassificationofLipids脂类的分类 B Complexlipids estersoffattyacidscontaininggroupsinadditiontoalcoholsandfattyacids1 Phospholipids磷脂 glycerol fattyacidsandphosphoricacidresidue甘油 脂肪酸和磷脂残渣2 Glycolipids糖脂 fattyacids sphingosine carbohydrateC Precursorandderivedlipids脂类的前体及衍生物1 Eicosanoids十二烷类2 Steroids类固醇3 Terepenes FATTYACIDS脂肪酸 A Generalstructure Acyl酰基chain C H andcarboxylicacid COOH B Saturatedorunsaturated饱和 不饱和1 Saturated nodoublebonds saturatedwithH 饱和没有双键2 Unsaturated contains1ormoredoublebonds不饱和有一个或更多的双键a Monounsaturated 1doublebond单一不饱和脂肪酸b Polyunsaturated 2ormoredoublebonds多不饱和脂肪酸Asnumberofdoublebondsincreases meltingpointdecreases 硬脂酸 十八酸 油酸 十八酸 亚麻油酸 十八酸 69 1C 13 2C 9C 硬脂酸 十八酸 油酸 十八酸 亚麻油酸 十八酸 FATTYACIDS脂肪酸 C Chainlength 1to24C 链长 Threegroupsbasedonchainlength shortchain 1to4C mediumchain 6to10C andlongchain 12to24C 短链 中链和长链 Aschainlengthincreases meltingpointincreases 随着碳链长度的增加 熔点是提高的 FattyacidssynthesizedbyplantsandanimalshaveanevennumberofC 通过植物和动物合成的脂肪酸具有偶数碳原子 Fattyacidswith2 aceticacid 3 propionicacid and4 butyricacid carbonsarecalledvolatilefattyacidsbecausetheyevaporateatroomtemperature 乙酸 丙酸和丁酸是室温下蒸发 称为挥发性脂肪酸 Mostfattyacidsinplantandanimaltissuearelongchain 动物和植物组织中多数的脂肪酸是长链 FattyAcids脂肪酸 D StructureoftheC chainGeometricalisomersofunsaturatedfattyacids不饱和脂肪酸的立体异构体a Cis顺式 occursnaturally causes bend inacylchain在酰基链上弯曲b trans反式 notcommon foundinhydrogenatedoils氢化油usedtomakemargarine人造奶油andfrombacterialsynthesis resultsin straight acylchain FattyAcids 2 Straightorbranchedchain直链或支链a Fattyacidssynthesizedbymammalsandplantsarestraightchains 哺乳动物和植物合成的脂肪酸是直链b Somefattyacidssynthesizedbybacteriaarebranchedchains 细菌合成的一些脂肪酸是支链的Straightchain C C C C C C COOHCBranchedchain C C C C C C COOH FattyAcidsNomenclature 1 Commonnames Example linoleic 2 SystematicnameExample 18Chydrocarbon octadecane18Csaturatedfattyacid octadecanoicacid18Cmonounsaturatedfattyacid 9 octadecenoicacid18Cpolyunsaturatedfattyacid9 12 octadecadienoicacid FattyAcidsNomenclature 3 Short hand methodsCarbonnumberingsystems endCarboxylend FattyAcidsNomenclature CH3 CH2 4CH CHCH2CH CH CH2 7COOHSystemsbasedoncountingcarbonsfromthecarboxylendNumeric Ex 9 12 18 2 Positionofdoublebonds numberofcarbons numberofdoublebonds9 12 18 2 Ex 18 2 9 12 Numberofcarbons Numberdoublebonds positionofdoublebonds18 2 9 12 FattyAcidsNomenclature CH3 CH2 4CH CHCH2CH CH CH2 7COOHSystemsbasedoncountingcarbonsfromthe endn Ex 18 2n 6 Numberofcarbons Numberdoublebondsn positionfirstdoublebond18 2n 6 Ex 18 2 6 18 2 6 Recordthenameofthisfattyacidusingall4shorthandmethods CH3CH2CH CHCH2CH CHCH2CH CHCH2CH2CH2CH2CH2CH2CH2CH2CH2COOHnumeric n Recordthenameofthisfattyacidusingall4shorthandmethods CH3CH2CH CHCH2CH CHCH2CH CHCH2CH2CH2CH2CH2CH2CH2CH2CH2COOHNumeric11 14 17 20 3 20 3 11 14 17n20 3n 3 20 3 3 Whichiscorrectforthisfattyacid 18 3omega 918 3delta9 12 1518 3n6Octodecatrianoicacid CH3CH2CH CHCH2CH CHCH2CH CH CH2 7COOH Whichiscorrectforthisfattyacid CH3CH2CH CHCH2CH CHCH2CH CH CH2 7COOH 18 3omega 318 3delta9 12 1518 3n 3Octodecatrienoicacid Wherenonumericvalueislisted theamountis 0 5 ofthetotalfattyacids Ingeneralwhichishigherinsaturatedfats AnimalproductslikemeatPlantproductsliketheoils EssentialFattyAcids Fattyacidsthatmustbeindietbecausetheanimalstissuecannotsynthesizethesefromotherprecursors Essentialfattyacidsarelinoleic 6family andlinolenicacid 3family Dietaryneedsforessentialfattyacidsareverylow verysmallchanceofadeficiencyinnormaldietsofanimalsorhumans EssentialFattyAcids Inadequateintakeof 3fattyacidslinolenic 18n 3 EPA 20 5n 3 andDHA 22 6n 3 isassociatedwithincreasedincidenceofheartdiseaseinhumans 3fattyacidsarehighinfishoilscoldwateralgaeishighinlinolenicacidwhichisconvertedtoEPAandDHAbyfish EssentialFattyAcids PhysicalTraitsofFattyAcids FormMembranes Micelles LiposomesandEmulsionsInaqueoussolutionsfattyacidsself orientatwater oilinterface Thisisduetohydrophobic non polargroup alkylchain andhydrophilic polargroup COOH beingonsamemolecule Lipidbilayeristhebasisforallmembranes Micellesareformedduringdigestionoffats Emulsionsarepossiblebyuseofemulsifyingagents Example lecithin Fattyacidsform soaps withmetals SodiumandpotassiumsoapsaresolubleinwaterCalciumandmagnesiumsoapsarealmostinsolubleinwaterInsolublesoapsarepoorlydigested feedingexcessivecalciumand ormagnesiumwilllowerdigestibilityoffats PhysicalTraitsofFattyAcids Unsaturatedfattyacidswillspontaneouslyoxidizewhenexposedtooxygen Calledauto oxidation氧化 peroxidation过氧化反应 orrancidity酸败 Occursduetometheleneinterrupteddoublebondsofunsaturatedfattyacids CH2CH CHCH2CH CH Freeradicalsformedduringperoxidationcandamagetissueinlivinganimalsorreducethenutritionalvalueoffatsinfeedstuffs PhysicalTraitsofFattyAcids Antioxidantsminimizeoxidation NaturalAntioxidantsVitaminEVitaminC carotene SyntheticAntioxidantsBHTBHAEthoxyquin PhysiologicalRolesofFattyAcids ConcentratedsourceofstoredenergyinanimalsandplantsCarbohydrate fatsorproteinconsumedinexcessofenergyneedswillbeconvertedtofattyacidsandstoredastriglyceridesinthefatcellsofadiposetissue Duringinadequateenergyintake fattyacidsarereleasedfromthefatcellsintothebloodandareusedforenergybymosttissues Onanequalweightbasis fatscontainovertwicetheenergyofcarbohydratesorproteins Adipocytes脂肪细胞 cellsinadiposetissuethatstoretriglycerides 细胞质 PhysiologicalRolesofFattyAcids Aspartoftriglyceridestheyarethebuildingblocksforthephospholipids磷脂andglycolipids糖脂 theprimaryconstituentsofcellmembranes Precursorsofmanybiologicallyactivecompoundssuchasprostanoids前列腺 cholesterol hormones etc Triglycerides Triacylglycerols Composedofglycerolandthreefattyacidsinanesterlinkage Triglyceridesmaycontainthreeofthesamefattyacid butusuallydifferentfattyacidsarepresentinatriglyceride Mostcommonformoflipidintissueandfeedstuffs 酯键 棕榈酸 脱水 三酰甘油 ComplexLipids复合脂类 Phospholipids磷脂 Glycerol 2fattyacids P04 NbaseNBaseisCholine胆碱Lecithin卵磷脂Ethanolamine乙醇胺Cephalin脑磷脂Functions membranes膜 lipoprotein脂蛋白Sphingosine鞘氨醇 fattyacid P04 NbaseFunctions Partofsphingomyelin鞘氨酯 acomponentofbrainandnervetissue Glycolipids糖脂 Sphingosine神经胺 fattyacid glucoseorgalactose aminosugar氨基糖Function Partofnervetissueandcellmembranes DerivedLipids Eiconsanoids postrnoids lipoxins脂氧素andleukotriences白三烯 Synthesizedfrom20CpolyunsaturatedfattyacidsWiderangeofmetabolicfunctions DerivedLipids Steroids类固醇Cholesterol胆固醇MajorcomponentofbrainandnervecellsPrecursorusedtosynthesizeVitaminD3 androgens etc Ergosterol麦角固醇Synthesizedbyplants itisaprecursorforVitaminD2 Bileacids胆汁酸PolarderivativesofcholesterolmadeintheliverNeededfordigestionoffats DerivedLipids Terpenes萜烯MadebyplantsCarotenoids类胡萝卜素 VitaminAprecursor Xanthophylls叶黄素 nonutritionalvalue providesyellowpigment黄色素 ImportanceofLipidsinAnimalandHumanNutrition Fatsandoilsarethepredominantlipidindiets Fatsandoilsarethemostconcentratedsourcesofenergy Asfatandoilcontentofadietorfeedstuffincreasestheamountofusableenergyincreases TypesofFatsandOilsFedtoAnimals ImportanceofLipidsinAnimalandHumanNutrition Linoleic亚麻油酸andlinolenicacid亚麻酸aredietaryessentials buthavelittlepracticalimportanceinanimalfeedingbecausetheneedsarelowandnaturalfeedscontainmorethanenoughtomeetthoseneeds ImportanceofLipidsinAnimalandHumanNutrition Fatsandoilsexposedtoairwilleventuallybecomerancid Antioxidants抗氧化剂areaddedtohighfatproductssuchasfeedgradeanimalfatandfishmealstoreducetherateofrancidity ImportanceofLipidsinAnimalandHumanNutrition Fatsareanessentialpartofhumandiets butexcessintakeofsaturatedfats primarilylauric月桂酸 myristic豆蔻酸 andpalmiticacid棕榈酸 increasestheincidenceofheartdisease TheAmericanHeartAssociationguidelinesforhealthyadultsare Totalfat 30 ofcaloriesSaturatedfattyacids 10 ofcalories Whichdietwouldhavethehighestenergycontent Diet1Diet2Can ttellAboutthesameenergycontent ImportantConceptsaboutLipids Lipidsarethemostconcentratedsourceofdi