圖書在版編目(CIP)數據生物化學簡明雙語教程:漢、英/陳夢玲,崔竹梅,翟春編.南京:南京大學出版社,2016.12(地方應用型本科教學內涵建設成果係列叢書)ISBN9787305179563Ⅰ.①生…Ⅱ.①陳…②崔…③翟…Ⅲ.①生物化學-雙語教學-高等學校-教材-漢、英Ⅳ.①Q5中國版本圖書館CIP數據核字(2016)第298523號出版發行南京大學出版社社址南京市漢口路22號郵編210093出版人金鑫榮叢書名地方應用型本科教學內涵建設成果係列叢書書名生物化學簡明雙語教程編者陳夢玲崔竹梅翟春責任編輯劉飛蔡文彬編輯熱線02583686531照排南京理工大學資產經營有限公司印刷虎彩印藝股份有限公司PPT:生物化學開本787×10921/16印張18.75字數433千簡明雙語教程版次2016年12月第1版2016年12月第1次印刷ISBN9787305179563定價42.00元網址:http://www.njupco.com官方微博:http://weibo.com/njupco微信服務號:njuyuexue銷售谘詢熱線:(025)83594756版權所有,侵權必究凡購買南大版圖書,如有印裝質量問題,請與所購圖書銷售部門聯係調換書前言全球經濟一體化、國際化的快速推進以及我國複合型人才培養的要求對高等教育產生了巨大影響。教育部2001年發布《關於加強高等學校本科教學工作提高教學質量的若幹意見》(4號文件)指出:逐步推廣和實行本科生教育中公共基礎課和專業必修課的雙語教學,是培養新時期我國複合型創新人才的重要基礎。2007年教育部啟動的“高等學校教學質量與教學改革工程”,將雙語課程建設作為拓寬大學生國際視野的一項重要措施。因此,對於高等學校開設雙語課程的必要性與重要性已經毋庸置疑。生物化學這門學科具有特殊性,其課程內容建立在英文基礎上,因為課程中的實驗和理論大多源於國外科學家的研究。此外,生物化學科學研究的最新進展也幾乎都以全英文的形式發表在相關的國際專業雜誌上。因此,高校開展雙語教學有利於學生在係統學習生物化學基礎理論的同時提高實際英文應用能力,獲取學科前沿知識以及掌握相關的專業英語詞彙和表達方式,成為更具有競爭能力的複合型創新人才。對於地方應用型本科高校而言,雙語教學顯得迫切且具有現實意義。

盡管我國各大高校雙語教學探索已有若幹年,但教材的跟進始終顯得滯後。沒有合適的教材是目前雙語教學麵臨的困難之一。雖然多數老牌高校喜歡直接采用外語原版教材,但對於地方應用型本科院校來說,單純使用外語原版教材往往會出現兩大問題:一是“水土不服”,外語原版教材中許多針對西方發達國家的案例不適合直接“拿來”;二是“篇幅大、閱讀難度大”,學生由此產生畏懼和退縮心理。另外,以英語原版教材作為主、以中文教材為輔的這種“複線型”教材形式存在缺陷,學生往往會依賴中文教材而忽視原版教材的學習。因此,編寫小組經過反複討論與征求學生意見,堅持以外文“原汁原味”為基礎,根據引進的經典英文原版教材改編,保證語言純正;同時考慮雙語教學的課時有限,隻選取本學科需要重點掌握的內容進行編寫,篇幅適中,減輕學生負擔。

生物化學是多個專業的基礎課,不同專業對該課程知識需求的側重不同。

本教材包括三大部分內容,即結構生物化學、新陳代謝和信息大分子。對於食品類專業而言,結構生物化學和新陳代謝是食品專業學生學習的重點,為後續001生物化學簡明雙語教程專業課程包括食品化學、食品營養學、食品分析、食品理化檢驗、食品保藏原理與技術以及功能性食品等奠定基礎。對於信息大分子這部分內容,則相對簡明扼要,有別於生命科學相關專業,突出應用型人才培養的理念。

本書圖文並茂,特別注重雙語教學的需要,兼顧學生參差不齊的英語水平,將重要的英文生化專業名詞與術語均在文中標出相應的中文。英文段落內容根據其難易程度采取兩種方式處理:簡單內容用中文進行段落大意歸納,複雜內容采用中文進行段落翻譯。本書主要參考的英文教材是TrudyMckee等主編的“Biochemistry:AnIntroduction(secondedition)”。此外,將部分中文教材的內容擇其精華編譯到本教材中。每個章節之後都附有關鍵詞彙表、思考題等。本書適用於地方應用型本科高校食品科學與工程、食品質量與安全、化學、農學、發酵工程、環境科學等專業進行中英雙語教學的學生使用。

由於編者水平有限,時間倉促,書中難免存在不足及疏漏之處,敬請讀者批評指正。

編者2016年8月002Introduction引言Introduction引言iochemistry,sometimescalledbiologicalchemistry,isthe生物化學的含義。

studyofchemicalprocessesinlivingorganisms(生物B體),including,butnotlimitedto,livingmatter.Biochemistrygovernsalllivingorganismsandlivingprocesses.Bycontrollinginformationflow(信息流)throughbiochemicalsignalling(生物化學信號)andtheflowofchemicalenergy(化學能量流)throughmetabolism(代謝),biochemicalprocessesgive生物化學研究對象的複riseto(導致)theincrediblecomplexity(難以置信的複雜性)of雜性。

life.Muchofbiochemistrydealswiththestructuresandfunctionsofcellularcomponentssuchasproteins(蛋白質),carbohydrates(糖),lipids(脂質),nucleicacids(核酸)andotherbiomolecules(生物分子)althoughincreasinglyprocessesratherthanindividualmoleculesarethemainfocus.Overthelast40yearsbiochemistryhasbecomesosuccessfulatexplainingliving生物化學的成就。

processesthatnowalmostallareasofthelifesciences(生命科學)frombotany(植物)tomedicine(醫學)areengagedin當今純粹生物化學的主biochemicalresearch.Todaythemainfocusofpure要焦點是了解生物分子在活細胞內如何工作,這biochemistry(純粹生物化學)isinunderstandinghowbiological極大地關係到對整個生moleculesgiverisetotheprocessesthatoccurwithinlivingcells物體的研究和理解。

whichinturnrelatesgreatlytothestudyandunderstandingofwholeorganisms.Amongthevastnumberofdifferentbiomolecules,many生物分子以及生物大分arecomplex(複合物)andlargemolecules(calledbiopolymers子的含義。

生物大分子,生物聚合物),whicharecomposedofsimilarrepeatingsubunits(亞單位)(calledmonomers單體).Eachclassofpolymericbiomoleculehasadifferentsetofsubunittypes.Forexample,aproteinisapolymerwhosesubunitsareselectedfromasetof20ormoreaminoacids(氨基酸).Biochemistrystudiesthechemicalproperties(化學性質)ofimportantbiologicalmolecules,likeproteins,andinparticularthechemistryofenzymecatalyzedreactions(酶促反應).001書生物化學簡明雙語教程Thebiochemistryofcellmetabolism(新陳代謝)andtheendocrinesystem(內分泌係統)hasbeenextensively(廣泛地)described.Otherareasofbiochemistryincludethegeneticcode(DNA,RNA)(遺傳密碼),proteinsynthesis(蛋白質合成),cellmembranetransport(細胞跨膜運輸),cellmembranetransferandsignaltransduction(信號轉導).人類對生命物質的認識Itoncewasgenerallybelievedthatlifeanditsmaterialshad過程。someessentialproperty(本質屬性)orsubstancedistinctfrom(不同於)anyfoundinnonlivingmatter(非生命物質),anditwasthoughtthatonlylivingbeings(有機體,生物)couldproducethemoleculesoflife.Then,in1828,FriedrichWohlerpublishedapaperonthesynthesisofurea(尿素合成),provingthatorganiccompounds(有機化合物)canbecreatedartificially(人工地).生物化學的起源及早期Thedawnofbiochemistry(生物化學的開端)mayhavebeen發展。thediscoveryofthefirstenzyme(酶),diastase(澱粉糖化酶)(todaycalledamylase澱粉酶),in1833byAnselmePayen.EduardBuchnercontributed(出版)thefirstdemonstration(論證)ofacomplexbiochemicalprocess(複雜的生化反應)outsideofacellin1896:alcoholicfermentation(乙醇發酵)incellextracts(細胞萃取物)ofyeast(酵母).Althoughtheterm“biochemistry”seemsto“生物化學”學科術語的havebeenfirstusedin1882,itisgenerallyacceptedthatthe確立。formalcoinage(正式使用)ofbiochemistryoccurredin1903byCarlNeuberg,aGermanchemist.Previously,thisareawouldhavebeenreferredtoas(被稱為)physiologicalchemistry(生理化學).Sincethen,biochemistryhasadvanced,especiallysince促使生物化學迅速發展themid20thcentury,withthedevelopmentofnewtechniques的諸多相關科學技術。suchaschromatography(色譜分析法),Xraydiffraction(X射線衍射),dualpolarisationinterferometry(雙偏振幹涉法),NMRspectroscopy(核磁共振波譜法),radioisotopiclabeling(放射性同位素的標記),electronmicroscopy(電子顯微鏡)andmoleculardynamicssimulations(分子動力學模擬).Thesetechniquesallowedforthediscoveryanddetailedanalysisofmanymoleculesandmetabolicpathways(代謝途徑)ofthecell,suchasglycolysis(糖酵解)andtheKrebscycle(citricacidcycle三羧酸循環).002Introduction引言Anothersignificanthistoricevent(有曆史意義的事件)in生物化學的分支,分子生biochemistryisthediscoveryofthegene(基因)anditsrolein物學的由來。

thetransferofinformationinthecell(在細胞信息傳遞中所起的作用).Thispartofbiochemistryisoftencalledmolecularbiology(分子生物學).Inthe1950s,JamesD.Watson,FrancisCrick,RosalindFranklin,andMauriceWilkinswere分子生物學的研究領域。

instrumental(有幫助的)insolvingDNAstructure(DNA結構)andsuggestingitsrelationshipwithgenetictransferofinformation(遺傳信息的傳遞).In1958,GeorgeBeadleandEdwardTatumreceivedtheNobelPrizeforworkinfungi(真菌)showingthatonegene(基因)producesoneenzyme(酶).In分子生物學研究成果及1988,ColinPitchforkwasthefirstpersonconvictedofmurder其應用。

(謀殺罪名成立)withDNAevidence(DNA證據),whichledtogrowthofforensicscience(司法鑒定).Morerecently,AndrewZ.FireandCraigC.Melloreceivedthe2006NobelPrizefordiscoveringtheroleofRNAinterference(RNAi)(RNA幹擾),inthesilencing(沉默)ofgeneexpression(基因表達).Today,therearethreemaintypesofbiochemistry.Plant生物化學的主要類型及biochemistry(植物生物化學)involvesthestudyofthe研究對象。

biochemistryofautotrophicorganisms(自養有機體)suchasphotosynthesis(光合作用)andotherplantspecificbiochemicalprocesses(特定的生化過程).Generalbiochemistry(普通生物化學)encompasses(包含)bothplantandanimalbiochemistry.Human/medical/medicinalbiochemistry(人體/醫療/醫藥生物化學)focusesonthebiochemistryofhumansandmedicalillnesses(疾病).Thefourmainclassesofmoleculesinbiochemistryare生物分子的類別。

carbohydrates,lipids,proteins,andnucleicacids.Manybiologicalmoleculesarepolymers(高分子聚合物):inthisterminology(術語),monomers(單分子)arerelativelysmallmicromolecules(小分子)thatarelinkedtogethertocreatelargemacromolecules(大分子),whichareknownaspolymers.Whenmonomersarelinkedtogethertosynthesize(合成)abiologicalpolymer,theyundergoaprocesscalleddehydrationsynthesis(脫水縮合).003PartIStructuralBiochemistry結構生物化學PartIStructuralBiochemistry結構生物化學Chapter1Carbohydrates糖類arbohydrate(pronounced/kɑ:bhadret/)isanorganic糖的化學組成。

compound(有機化合物)withtheempiricalformula(通)()();C式CmH2Onwheremcouldbedifferentfromnthatis,consistsonlyofcarbon,hydrogen,andoxygen(僅由C、H、O組成),withahydrogen:oxygenatomratio(氫氧原子比)of2∶1(asinwater).Carbohydratescanbeviewedashydrates(水合物)ofcarbon,hencetheirname.Structurallyhowever,itismoreaccuratetoviewthemaspolyhydroxyaldehydesandketones(多羥基的醛和酮).Thetermismostcommoninbiochemistry,whereitisa糖的分類。

synonym(同義詞)ofsaccharide(糖).Thecarbohydrates(saccharides)aredividedintofourchemicalgroupings:monosaccharides(單糖),disaccharides(二糖),oligosaccharides(寡糖),andpolysaccharides(多糖).Ingeneral,themonosaccharidesanddisaccharides,whicharesmaller(lowermolecularweight)carbohydrates,arecommonlyreferredtoassugars.ThewordsaccharidecomesfromtheGreekwordσκχαρον(skkharon),meaning“sugar”.Whilethescientificnomenclature(術語)ofcarbohydratesiscomplex,thenamesofthemonosaccharidesanddisaccharidesveryoftenendinthesuffixose(單糖、二糖通常以後綴ose結尾).Forexample,bloodsugaristhemonosaccharideglucose,tablesugar(蔗糖)isthedisaccharidesucrose,andmilksugaristhedisaccharidelactose(seeillustration(插圖)).乳糖是一種在牛奶中發現的二糖。它由一分子D半乳糖和一分子D葡萄糖通過β14糖苷鍵組成。

Lactoseisadisaccharidefoundinmilk.ItconsistsofamoleculeofDgalactoseandamoleculeofDglucosebondedbybeta14glycosidiclinkage.IthasaformulaofC12H22O11.007生物化學簡明雙語教程Carbohydratesperformnumerousroles(多種角色)inlivingthings.Polysaccharidesserveforthestorageofenergy(貯藏能糖類在生命體中的重要量)(e.g.,starch(澱粉)andglycogen(糖原)),andas作用。structuralcomponents(結構成分)(e.g.,celluloseinplants(植物中的纖維素)andchitininarthropods(節肢動物中的幾丁質)).The5carbonmonosaccharideribose(核糖)isanimportantcomponentofcoenzymes(輔酶)(e.g.,ATP,FAD,andNAD)andthebackbone(主鏈)ofthegeneticmolecule(遺傳分子)knownasRNA.Therelateddeoxyribose(脫氧核糖)isacomponentofDNA.Saccharidesandtheirderivatives(衍生物)includemanyotherimportantbiomoleculesthatplaykeyroles(重要角色)intheimmunesystem(免疫係統),fertilization(受精),preventingpathogenesis(抗病原體),bloodclotting(血液凝固),anddevelopment(發育).Infoodscience(食品科學)andinmanyinformalcontexts(日常生活中),thetermcarbohydrateoften糖類是食品的重要組成meansanyfoodthatisparticularlyrichinthecomplex成分。carbohydratestarch(suchascereals,bread,andpasta)(在糖澱粉複合物中含量豐富,例如穀類、麵包、麵食)orsimplecarbohydrates,suchassugar(foundincandy,jams(果醬),anddesserts(甜點)).11Structure結構以前化學家認為具有通Formerly(以前)thename“carbohydrate”wasusedin式()的化合物CmH2Onchemistryforanycompound(化合物)withtheformula是糖類,據此一些化學家Cm(H2O)n.Followingthisdefinition(由於這個定義),some認為甲醛是最簡單的糖。

chemistsconsideredformaldehyde(甲醛)CH2Otobethe目前“糖”這個術語的生物simplestcarbohydrate,whileothersclaimedthattitlefor學意義,把僅含有一個或lcolaldehde(羥乙醛).Todathetermisenerall兩個碳原子的化合物排gyyygy(),除在外。understoodinthebiochemistrysense生物學意義whichexcludes(除了)compoundswithonlyoneortwocarbons.Natural(自然界)saccharidesaregenerallybuiltof(由……組成)simplecarbohydratescalledmonosaccharideswithgeneral008PartIStructuralBiochemistry結構生物化學。

formula(CH2O)nwherenisthreeormore.Atypical(典型的)自然界中的糖monosaccharidehasthestructureH—(CHOH)x(CO)—(CHOH)y—H,thatis,analdehyde(醛)orketone(酮)withmanyhydroxylgroups(羥基)added,usuallyoneoneachcarbonatomthatisnotpartofthealdehydeorketonefunctionalgroup(官能團).Examplesofmonosaccharidesareglucose(葡萄糖),fructose(果糖),andglyceraldehyde(甘油醛).However,somebiologicalsubstancescommonlycalled“monosaccharides”donotconformtothisformula(不符合通式)(e.g.,uronicacids(糖醛酸)anddeoxysugars(脫氧糖)suchasfucose(海藻糖)),andtherearemanychemicals(化學品)thatdoconformtothisformulabutarenotconsideredtobemonosaccharides(e.g.,formaldehydeCH2Oandinositol(肌糖、纖維糖)(CH2O)6).Theopenchainform(開鏈型)ofamonosaccharideoften開鏈型的單糖常與其閉coexistswith(共存)aclosedringform(閉環型)wherethe環型共存。在閉環型單糖中,其醛或酮基上的羰基aldehyde/ketonecarbonyl(羰基)groupcarbon(CO)and碳原子與羥基反應生成hydroxylgroup(羥基)(—OH)reactformingahemiacetal(半縮半縮醛,形成新的C—醛)withanewC—O—Cbridge.O—C連接鍵。

Monosaccharidescanbelinkedtogetherintowhatare單糖不僅是重要的能源calledpolysaccharides(oroligosaccharides)inalargevarietyof分子,還是核酸的組成成分。

ways(各種各樣的方法).Manycarbohydratescontain(包含)oneormoremodified(修飾的)monosaccharideunits(單元)thathavehadoneormoregroupsreplacedorremoved.Forexample,deoxyribose(脫氧核糖)acomponentofDNA,isamodifiedversionofribose;chitin(幾丁質)iscomposedofrepeatingunits(重複單元)ofNacetylglucosamine(N乙酰葡糖胺),anitrogencontainingformofglucose(一個含氮形式的葡萄糖).12Monosaccharides單糖Monosaccharidesarethesimplestcarbohydratesinthattheycantbehydrolyzed(水解)tosmallercarbohydrates.Theyarealdehydesorketoneswithtwoormorehydroxylgroups.009生物化學簡明雙語教程Thegeneralchemicalformulaofanunmodifiedmonosaccharideis(CH2O)n,literallya“carbonhydrate(碳的水合物)”.Monosaccharidesareimportantfuel(燃料)moleculesaswellasbuildingblocks(組成成分)fornucleicacids(核酸).Thesmallestmonosaccharides,forwhichn=3,aredihydroxyacetone(二羥基丙酮)andDandLglyceraldehyde(甘油醛).D葡萄糖是一種己醛糖,4分子式為(CH2O)6。C上連接的—OH位於費歇爾投影式右側,故為D4Dglucoseisanaldohexosewiththeformula(CH2O)6.becauseC—OH型糖。

isontherightoftheFischerprojection,thisisaDsugar.121Classificationofmonosaccharides單糖的分類單糖分類的三種依據:羰Monosaccharidesareclassifiedaccordingto(根據)three基類型、碳原子數目、differentcharacteristics(特點):theplacement(定位)ofits手性。

carbonylgroup,thenumberofcarbonatomsitcontains(包含),anditschiralhandedness(手性).Ifthecarbonylgroupisanaldehyde,themonosaccharideisanaldose(醛糖);ifthecarbonylgroupisaketone,themonosaccharideisaketose(酮糖).Monosaccharideswiththreecarbonatomsarecalledtrioses(丙糖),thosewithfourarecalledtetroses(四糖),fivearecalledpentoses(戊糖),sixarehexoses(己糖),andsoon.Thesetwosystemsofclassificationareoftencombined(聯合).Forexample,glucoseisanaldohexose(己醛糖)(asixcarbonaldehyde),riboseisanaldopentose(戊醛糖)(afivecarbonaldehyde),andfructose(果糖)isaketohexose(己酮糖)(asixcarbonketone).單糖的多個不對稱中心Eachcarbonatombearing(具有)ahydroxylgroup導致有多種立體異構體。(—OH),withtheexception(例外)ofthefirstandlastcarbons,areasymmetric(不對稱的),makingthemstereocenters(立體中心)withtwopossibleconfigurations(構010PartIStructuralBiochemistry結構生物化學型)each(RorS).Becauseofthisasymmetry(不對稱),anumberofisomers(異構體)mayexistforanygivenmonosaccharideformula.Thealdohexose(己醛醣)Dglucose,forexample,hastheformula(CH2O)6,ofwhichallbuttwoofitssixcarbonsatomsarestereogenic(對稱的),makingDglucoseoneof24=16possiblestereoisomers(立體異構體).Inthecaseofglyceraldehyde(甘油醛),analdotriose(丙醛糖),thereisonepairofpossiblestereoisomers,whichareenantiomers(對映異構體)andepimers(差向異構體).1,3dihydroxyacetone(二羥基丙酮),theketosecorrespondingto(相對於)thealdoseglyceraldehyde,isasymmetric(對稱的)moleculewithnostereocenters.Theassignment(分配)ofDorLismadeaccordingtotheorientation(方向,定位)oftheD或L型取決於離羰基asymmetriccarbonfurthestfromthecarbonylgroup:ina最遠的非對稱碳的取向。

standardFischerprojectionifthehydroxylgroupisontherightthemoleculeisaDsugar,otherwise(否則)itisanLsugar.The“D”and“L”prefixes(前綴)shouldnotbeconfusedwith“d”or“l”,whichindicate(表示)thedirection(方向)thatthesugarrotatesplanepolarizedlight(平麵偏振光).Thisusage(使用)of“d”and“l”isnolongerfollowedincarbohydratechemistry(不再適用於糖化學).葡萄糖的α和β型異頭物。注意異頭碳(即1號碳)上的羥基與5號碳上連接的CH2OH基團的位置關係:若在異側為α型,Theαandβanomers(異頭物)ofglucose.Notethepositionofthe。

hydroxylgroupontheanomericcarbon(異頭碳)relativetotheCH2OHgroup若在同側為β型boundtocarbon5:theyareeitherontheoppositesides(異側)(α),orthesameside(同側)(β).122Ringstraightchainisomerism環直鏈異構現象直鏈單糖的醛基或酮基Thealdehdeorketonerouofastraihtchain(直鏈)ygpg可與其他碳上的羥基發()monosaccharidewillreactreversibly可逆反應withahydroxyl生可逆反應,生成半縮醛grouponadifferentcarbonatomtoformahemiacetal(半縮醛)或半縮酮,形成氧原子橋orhemiketal(半縮酮),formingaheterocyclicring(雜環)with接兩個碳原子(即C—anoxygenbridgebetweentwocarbonatoms.RingswithfiveO—C)形式的雜環。

011生物化學簡明雙語教程andsixatomsarecalledfuranose(呋喃糖)andpyranose(吡喃糖)forms,respectively(分別地),andexistinequilibrium(平衡)withthestraightchainform(直鏈形式).Duringtheconversion(轉換)fromstraightchainformtothecyclic(環的)form,thecarbonatomcontainingthecarbonyloxygen(羰基氧原子),calledtheanomericcarbon(異頭碳),異頭物及其判斷標準。becomesastereogeniccenter(立體中心)withtwopossibleconfigurations:theoxygenatommaytakeapositioneitheraboveorbelowtheplaneofthering(環平麵).Theresultingpossiblepairofstereoisomersarecalledanomers(由此產生的可能的一對立體異構體被稱為異頭物).Intheαanomer(α異頭物),the—OHsubstituent(取代基)ontheanomericcarbonrests(靜止)ontheoppositeside(trans)oftheringfromtheα異頭物中,異頭碳上的—CH2OHsidebranch(分支).Thealternativeform(另一種形取代基與環上的OH式),inwhichtheCH2OHsubstituentandtheanomeric分支處於相對的CH2OHhydroxylareonthesameside(cis)oftheplaneofthering,is位置(反式),而另一種形calledtheβanomer(取代基、異頭羥基連在一起的(cis)平麵環,式為兩者處於環平麵的同稱為β異頭物).Becausetheringandstraightchainforms側(順式),稱為β異頭物。

readilyinterconvert(互變),bothanomersexistinequilibrium(平衡存在).123Useinlivingorganisms生物體中的用途生物體中單糖是主要的Monosaccharidesarethemajorsourceoffuelfor能量來源。metabolism(代謝燃料的主要來源),beingusedbothasanenergysource(能源)(glucosebeingthemostimportantinnature)andinbiosynthesis(生物合成).Whenmonosaccharidesarenotimmediatelyneeded(立即需要)bymanycellstheyareoftenconvertedto(轉換)morespaceefficientforms(有效形式),oftenpolysaccharides.Inmanyanimals,includinghumans,thisstorageform(儲存形式)isglycogen(糖原),especiallyinliverandmusclecells(肝髒和肌肉細胞).Inplants(植物中),starch(澱粉)isusedforthesamepurpose.012PartIStructuralBiochemistry結構生物化學13Disaccharides二糖Twojoinedmonosaccharidesarecalledadisaccharide(二糖)andthesearethesimplestpolysaccharides(多糖).Examplesincludesucrose(蔗糖)andlactose(乳糖).Theyarecomposedoftwomonosaccharideunitsboundtogetherbyacovalentbond(共價鍵)knownasaglycosidiclinkage(糖苷鍵)兩個單糖經過脫水反應formedvia(通過)adehydrationreaction(脫水反應),resulting通過糖苷鍵連接形成。

in(導致)thelossofahydrogenatom(損失一個氫原子)from二糖onemonosaccharideandahydroxylgroup(羥基)fromtheother.Theformulaofunmodified(未修飾的)disaccharidesisC12H22O11.Althoughtherearenumerouskindsof(多種)disaccharides,ahandfulof(少量)disaccharidesareparticularlynotable(引人注目).Sucrose,alsoknownastablesugar,isacommondisaccharide.Sucrose(蔗糖),picturedabove,isthemostabundant(最豐蔗糖是最豐富的二糖。

富的)disaccharide,andthemainforminwhichcarbohydratesaretransportedinplants(植物中糖類運輸的主要形式).ItiscomposedofoneDglucosemoleculeandoneDfructosemolecule.Thesystematicnameforsucrose(蔗糖的係統命名),蔗糖由D葡萄糖與DOαDglucopyranosyl(1→2)Dfructofuranoside,果糖組成。

indicatesfourthings:(1)Itsmonosaccharides(單糖):glucose(葡萄糖)andfructose.蔗糖係統命名包含四種(2)Theirringtypes(環類型):glucoseisapyranose(吡喃信息。

),()糖andfructoseisafuranose呋喃糖.連接方式:αD葡萄糖(3)Howtheyarelinkedtogether:theoxygenoncarbon的一號碳(C1)上的氧連12number1(C)ofαDglucoseislinkedtotheCofD接D果糖的二號碳fructose.(C2)。

013生物化學簡明雙語教程(4)Theosidesuffix(後綴)indicatesthattheanomericcarbon(異頭碳)ofbothmonosaccharidesparticipatesin(參與)theglycosidicbond(糖苷鍵).Lactose(乳糖),adisaccharidecomposedofoneD常見二糖名稱及組成。galactose(半乳糖)moleculeandoneDglucosemolecule,occursnaturallyin(天然存在於)mammalian(哺乳動物)milk.ThesystematicnameforlactoseisOβDgalactopyranosyl(1→4)Dglucopyranose.Othernotabledisaccharidesincludemaltose(麥芽糖)(twoDglucoseslinkedα1,4)andcellulobiose(纖維二糖)(twoDglucoseslinkedβ1,4).disaccharidescanbeclassifiedintotwotypes.Theyarereducingandnonreducingdisaccahrides.Ifthefunctionalgroup(官能團)ispresentinbondingwithanothersugarunit,itiscalledasreducingdisaccharide(還原二糖).14Oligosaccharidesandpolysaccharides寡糖及多糖寡糖和多糖是由單糖單Oligosaccharides(寡糖)andpolysaccharides(多糖)are元通過糖苷鍵連接形成composedoflongerchains(長鏈)ofmonosaccharideunitsbound的長鏈組成。

togetherbyglycosidicbonds(糖苷鍵).Thedistinction(區別)betweenthetwoisbasedupon(基於)thenumberofmonosaccharideunitspresentinthechain.Oligosaccharidestypicallycontainbetweenthreeandtenmonosaccharideunits,andpolysaccharidescontaingreaterthantenmonosaccharideunits.直鏈澱粉是由葡萄糖主要通過α(1→4)鍵連接形成的線性聚合物。它可以由幾千個葡萄糖單元組成,是澱粉的兩種成分之一,另一種是支鏈澱粉。

Amyloseisalinearpolymerofglucosemainlylinkedwithα(1→4)bonds.Itcanbemadeofseveralthousandsofglucoseunits.Itisoneofthetwocomponentsofstarch,theotherbeingamylopectin.014PartIStructuralBiochemistry結構生物化學Oligosaccharidesarefoundasacommonformofprotein寡糖是蛋白質翻譯後修posttranslationalmodification(翻譯後修飾).Polysaccharides飾的常見形式。

representanimportantclassofbiologicalpolymers(生物聚合物).Polysaccharidesarepolymericcarbohydratestructures,formedofrepeatingunits(重複單元)(eithermonoordi多糖的結構特點saccharides)joinedtogetherbyglycosidicbonds(糖苷鍵).Thesestructuresareoftenlinear(線性的),butmaycontainvariousdegreesofbranching(不同程度的分支).Polysaccharidesareoftenquiteheterogeneous(成分混雜的),containingslight(輕微的)modificationsoftherepeatingunit.Dependingonthestructure,thesemacromoleculescanhavedistinctproperties(不同屬性)fromtheirmonosaccharidebuildingblocks(構成單元).Theymaybeamorphous(無定形的)oreveninsolubleinwater(不溶於水).Whenallthemonosaccharidesinapolysaccharidearethesametypethepolysaccharideiscalledahomopolysaccharide(同多糖)orhomoglycan,butwhenmorethanonetypeof同多糖與雜多糖的區別。

monosaccharideispresenttheyarecalledheteropolysaccharides(雜多糖)orheteroglycans.Examplesincludestorage(儲存)polysaccharidessuchasstarchandglycogen(糖原),andstructuralpolysaccharides(結構性多糖)suchascellulose(纖維素)andchitin(幾丁質).Polysaccharideshaveageneralformula(一般通式)of多糖的化學通式。

Cx(H2O)ywherexisusuallyalargenumberbetween200and2500.Consideringthattherepeatingunitsinthepolymerbackbone(主幹)areoftensixcarbonmonosaccharides,thegeneralformulacanalsoberepresentedas(C6H10O5)nwhere40≤n≤3000.141Storagepolysaccharides儲存多糖(1)Starches澱粉Starchesareglucosepolymers(葡萄糖聚合物)inwhichglucopyranose(吡喃葡萄糖)unitsarebondedbyalphalinkages.Itismadeupofamixture(混合)ofAmylose(直鏈澱015生物化學簡明雙語教程粉)(15%~20%)andAmylopectin(支鏈澱粉)(80%~85%).澱粉分為直鏈澱粉和支Amyloseconsistsofalinearchain(直鏈)ofseveralhundred鏈澱粉,可通過澱粉酶水glucosemoleculesandamylopectinisabranchedmoleculemade。

解消化ofseveralthousandglucoseunits(everychain24~30glucoseunits).Starchesareinsolubleinwater.Theycanbedigestedbyhydrolysis(水解),catalyzed(催化)byenzymescalledamylases(澱粉酶),whichcanbreak(打破)thealphalinkages(glycosidicbonds)(糖苷鍵).Humansandotheranimalshaveamylases,sotheycandigeststarches.Potato(馬鈴薯),rice,wheat(小麥),andmaize(玉米)aremajorsourcesofstarchinthehumandiet(飲食).Theformationofstarchesarethewaythatplantsstoreglucose.(2)Glycogen糖原糖原的組成,分布及基本Glycogenisapolysaccharidethatisfoundinanimalsandis性質。composedofabranchedchain(支鏈)ofglucoseresidues(殘基).Itisstoredinliver(肝髒)andmuscles(肌肉).Itisanenergyreserve(儲備)foranimals.Itisthechief(主要)formofcarbohydratestoredinanimalbody.Itisinsoluble(不溶)inwater.Itgivesredcolourwithiodine(碘).Italsoyields(產生)glucoseonhydrolysis(水解).糖原分子結構圖。

Glycogen.142Structuralpolysaccharides結構多糖纖維素是植物細胞壁的(1)Cellulose纖維素主要結構組分。Celluloseisusedinthecellwalls(細胞壁)ofplantsand016PartIStructuralBiochemistry結構生物化學otherorganisms,andisclaimedtobethemostabundantorganicmolecule(有機分子)onearth.Ithasmanyusessuchasasignificantroleinthepaperandtextileindustries(紡織行業),andisusedasafeedstock(原料)fortheproductionofrayon(人造絲)(viatheviscoseprocess通過粘膠過程),celluloseacetate(醋酸纖維素),celluloid(賽璐珞),andnitrocellulose(硝化纖維).Thestructuralcomponent(結構組分)ofplantsareformedprimarily(主要)fromcellulose.Wood(木材)islargelycellulose(纖維素)andlignin(木質素),whilepaperandcottonarenearlypure(純的)cellulose.Celluloseisapolymer(聚合物)madewithrepeatedglucoseunitsbondedtogetherbybetalinkages.Humansandmanyotheranimalslack(缺少)an人類及許多動物缺少能enzymetobreakthebetalinkages,sotheydonotdigest斷開β鏈的酶而不能消化纖維素。能消化纖維素的cellulose.Certainanimalscandigestcellulose,becausebacteria一些動物是因為它們腸(細菌)possessingtheenzymearepresentintheirgut(腸道).道內存在能產生消化酶Theclassicexampleisthetermite(白蟻).Itisinsolublein的細菌。

water.Itgivesnocolorwithiodine(遇碘不變色).Onhydrolysis(水解),ityieldsglucose.Itisthemostabundantcarbohydrateinnature.纖維素的三維結構,它是一種β葡聚糖。

3Dstructureofcellulose,abetaglucanpolysaccharide.(2)Chitin幾丁質Chitinisoneofmanynaturallyoccurringpolymers(天然聚幾丁質(甲殼素)是天然聚合物).Itisoneofthemostabundantnaturalmaterialsinthe合物之一,由幾丁質酶催化分解。它與纖維素結構world.Overtime(隨著時間的推移)itisbiodegradable(生物可類似,都是保護有機體的降解)inthenaturalenvironment.Itsbreakdownmaybe結構材料。

catalyzedbyenzymescalledchitinases(幾丁質酶),secreted(分泌)bymicroorganisms(微生物)suchasbacteria(細菌)andfungi(真菌),andproducedbysomeplants.Someofthesemicroorganismshavereceptors(受體)tosimplesugarsfromthedecomposition(分解)ofchitin.Ifchitinisdetected,theythen017生物化學簡明雙語教程produceenzymestodigestitbycleaving(切開)theglycosidicbonds(糖苷鍵)inordertoconvertittosimplesugarsandammonia(氨).Chemically,chitiniscloselyrelatedtochitosan(殼聚糖)(amorewatersolublederivativeofchitin水溶性更強的幾丁質衍生物).Itisalsocloselyrelatedtocelluloseinthatitisalongunbranchedchainofglucosederivatives(葡萄糖衍生物的無分支長鏈).Bothmaterialscontributestructureandstrength,protectingtheorganism.(3)Pectins果膠果膠是複合多糖,主要存Pectinsareafamilyofcomplexpolysaccharidesthatcontain在於陸生植物細胞壁。1,4linkedDgalactosyluronicacidresidues(殘基).Theyarepresentinmostprimarycellwalls(細胞壁)andinthenonwoodypartsofterrestrialplants(陸生植物).(4)Acidicpolysaccharides酸性多糖酸性多糖含有羧基、磷酸Acidicpolysaccharidesarepolysaccharidesthatcontain基、硫酸酯基。carboxylgroups(羧基),phosphategroups(磷酸基)and/orsulfuricestergroups(硫酸酯基).(5)Bacterialpolysaccharides細菌多糖Bacterial(細菌)polysaccharidesrepresentadiverserange(不同的範圍)ofmacromolecules(大分子)thatinclude細菌多糖的分類、結構及peptidoglycan(肽聚糖),lipopolysaccharides(脂多糖),capsules生物作用。(莢膜)andexopolysaccharides(胞外多糖);compoundswhosefunctionsrangefromstructuralcellwallcomponents(e.g.,peptidoglycan),andimportantvirulencefactors(致病因素)(e.g.,PolyNacetylglucosamine(乙酰氨基葡萄糖)inS.aureus(金黃色葡萄球菌)),topermittingthebacteriumtosurvive(存活)inharshenvironments(惡劣環境)(e.g.,Pseudomonasaeruginosa(銅綠假單胞菌)inthehumanlung).Polysaccharidebiosynthesis(生物合成)isatightlyregulated(嚴格監管),energyintensiveprocess(能源密集型過程)andunderstanding多糖的生物合成研究有thesubtleinterplay(巧妙的相互作用)betweentheregulation巨大的研究空間、價值和(調控)andenergyconservation(保護),polymermodification意義。

(聚合物改性)andsynthesis(合成),andtheexternalecologicalfunctions(外部生態功能)isahugeareaofresearch(巨大的研究018PartIStructuralBiochemistry結構生物化學領域).Thepotential(潛在的)benefitsareenormous(巨大的)andshouldenableforexamplethedevelopmentofnovelantibacterial(抗菌)strategies(策略)(e.g.,newantibiotics(抗生素)andvaccines(疫苗))andthecommercialexploitation(商業開發)todevelopnovelapplications(新應用).(6)Bacterialcapsularpolysaccharides細菌莢膜多糖Pathogenicbacteria(病原菌)commonlyproduceathick(厚細菌莢膜多糖性質及結的),mucouslike(黏液樣的),layerofpolysaccharide.This構多樣性。

“capsule”(莢膜)cloaks(掩蓋)antigenicproteins(抗原蛋白)onthebacterialsurface(細菌表麵)thatwouldotherwiseprovoke(激起)animmuneresponse(免疫反應)andtherebyleadtothedestruction(破壞)ofthebacteria.Capsularpolysaccharidesarewatersoluble,commonlyacidic(酸性),andhavemolecularweights(分子量)ontheorderof100~1000kDa.Theyarelinear(線性)andconsistofregularly(有規律的)repeatingsubunits(亞基)ofonetosixmonosaccharides.Thereisenormousstructuraldiversity(巨大的結構多樣性);nearlytwohundreddifferentpolysaccharidesareproducedbyE.Coli(大腸杆菌)alone.Mixtures(混合物)ofcapsularpolysaccharides,eitherconjugated(結合的)ornative(天然的)areusedasvaccines(疫苗).Bacteriaandmanyothermicrobes(微生物),includingfungi(真菌)andalgae(藻類),oftensecrete(分泌)polysaccharidesasanevolutionaryadaptation(進化適應)to多糖對細菌、微生物的生helpthemadhere(堅持)tosurfaces(表麵)andtopreventthem物意義及人類開發的多。

fromdryingout(喪失水分).Humanshavedevelopedsomeof糖產品thesepolysaccharidesintousefulproducts,includingxanthangum(黃原膠),dextran(右旋糖酐),welangum(文萊膠),gellangum(結冷膠)andpullulan(普魯蘭多糖).Mostofthesepolysaccharidesexhibit(表現出)interestingandveryusefulviscoelasticproperties(黏彈性特性)whendissolvedinwateratverylowlevels(非常低的水平).This多糖的物理特性及其givesmanyfoodsandvariousliquidconsumerproducts(各種液應用。

體消費品),likelotions(乳液),cleaners(清潔劑)andpaints(油漆),forexample,aviscous(黏性)appearancewhenstationary019生物化學簡明雙語教程(靜止的),butfluidity(流動性)whentheslightestshear(最輕微的剪切)isapplied,suchaswhenwiped(擦拭),poured(倒)orbrushed(刷).Thispropertyisreferredtoaspseudoplasticity(假塑性),orshearthinning(剪切稀化).Aqueoussolutions(水溶液)ofthepolysaccharidealonehaveacuriousbehavior(奇怪的行為)whenstirred(攪拌).Afterstopping,theswirl(漩渦)continuesduetomomentum(動量),thenstops,andthenreversesdirection(逆轉方向)briefly(短暫地).Thisrecoil(反衝)demonstrates(表明)theelasticeffect(彈性效應)ofthepolysaccharidechainspreviouslystreched(之前被拉伸)insolution,returningtotheirrelaxedstate.Cellsurface(細胞表麵)polysaccharidesplaydiverserolesinbacterialecologyandphysiology(細菌生態學和生理學).Theyserveasabarrier(障礙)betweenthecellwallandtheenvironment,mediatehostpathogeninteractions(調解寄主病細胞表麵多糖在細菌生原體相互作用),andformstructuralcomponentsofbiofilms(生態學和生理學方麵的物膜).Thesepolysaccharidesaresynthesizedfromnucleotide作用。

activatedprecursors(核苷酸激活的前體)(callednucleotidesugars核苷酸糖)and,inmostcases,alltheenzymesnecessaryforbiosynthesis(生物合成),assembly(組裝)andtransport(運輸)ofthecompletedpolymerareencoded(編碼)bygenesorganizedindedicatedclusters(特定簇)withinthegenome(基因組)oftheorganism.Lipopolysaccharide(脂多糖)isoneofthemostimportantcellsurfacepolysaccharides,asitplaysakey(關鍵的)structuralroleinoutermembraneintegrity(外膜的完整性),aswellasbeinganimportantmediator(中介)ofhostpathogen(寄主病原體)interactions.【Keywords】saccharide糖glucose葡萄糖aldehyde醛galactose半乳糖ketone酮sucrose蔗糖aldose醛糖maltose麥芽糖ketose酮糖lactose乳糖monosaccharide單糖glycoside糖苷020PartIStructuralBiochemistry結構生物化學(續表)disaccharide二糖aglycosidicbond糖苷鍵trisaccharide三糖hydroxylgroup羥基oligosaccharide寡糖starch澱粉polysaccharide多糖amylose直鏈澱粉homopolysaccharide同多糖amylopectin支鏈澱粉heteropolysaccharide雜多糖glycogen糖原stereoisomer立體異構體cellulose纖維素anomer異頭物chitin殼多糖,幾丁質,甲殼素conformation構象glycoprotein糖蛋白isomerization異構化proteoglycan蛋白聚糖fructose果糖lipopolysaccharide脂多糖Questions1Describethetermsofhomopolysaccharides,heteropolysaccharides,glycosidicbond,stereoisomer,andanomer.2Whyhumanscannotdigestcellulosewell?

3Comparethestructuraldifferencesbetweenstarchandglycogen.References[1]McKeeTrudy,RMcKeeJames.Biochemistry:AnIntroduction(SecondEdition)[M].NewYork:McGrawHillCompanies,1999.[2]NelsonDL,CoxMM.LehningerPrinciplesofBiochemistry(ThirdEdition)[M].Derbyshire:WorthPublishers,2000.[3]DingW,JiaHT.Biochemistry(FirstEdition)[M].Beijing:HigherEducationPress,2012.[4]鄭集,陳鈞輝.普通生物化學(第四版)[M].北京:高等教育出版社,2007.[5]王豔萍.生物化學[M].北京:中國輕工業出版社,2013.021生物化學簡明雙語教程Chapter2Lipids脂質脂質的分類。ipidsareabroadgroupofnaturallyoccurringmoleculeswhichincludesfats,waxes(蠟),sterols(植物固醇),fatLsolublevitamins(脂溶性維生素)(suchasvitaminsA,D,EandK),monoglycerides(單甘酯),diglycerides(雙甘酯),脂質的生物功能。phospholipids(磷脂),andothers.Themainbiologicalfunctionsoflipidsincludeenergystorage,asstructural(結構)componentsofcellmembranes(細胞膜),andasimportantsignalingmolecules(信號分子).一些常見脂質的結構。最上麵是油酸和膽固醇的結構式,中間是甘油三酯的結構,它是由油酰、硬脂酰和棕櫚酰連接甘油主體形成的。底部是常見的磷脂,卵磷脂(磷脂酰膽堿)。

Structuresofsomecommonlipids.Atthetopareoleicacidandcholesterol.Themiddlestructureisatriglyceridecomposedofoleoyl,stearoyl,andpalmitoylchainsattachedtoaglycerolbackbone.Atthebottomisthecommonphospholipid,phosphatidylcholine.Lipidsmaybebroadlydefinedashydrophobic(疏水性)oramphiphilic(兩親性)smallmolecules;theamphiphilicnatureofsomelipidsallowsthemtoformstructuressuchasvesicles(囊生物脂質依據結構單元泡),liposomes(脂質體),ormembranesinanaqueous的分類。environment(疏水環境).Biologicallipidsoriginateentirelyorinpartfromtwodistincttypesofbiochemicalsubunits(子單元)or“buildingblocks”:ketoacyl(酮酯酰)andisoprene(異戊二022PartIStructuralBiochemistry結構生物化學烯)groups.Usingthisapproach,lipidsmaybedividedintoeightcategories(類別):fattyacyls(脂肪酰類),glycerolipids(甘油酯),glycerophospholipids(甘油磷脂),sphingolipids(鞘脂類),saccharolipidsandpolyketides(聚酮類)(derivedfromcondensation(縮合)ofketoacyl(酮酯酰)subunits);andsterollipids(甾醇脂)andprenollipids(戊烯醇脂)(derivedfromcondensationofisoprenesubunits).Althoughthetermlipidissometimesusedasasynonym(同脂質和脂肪的區別。

義詞)forfats,fatsareasubgroup(一群)oflipidscalledtriglycerides(甘油三酯).Lipidsalsoencompass(包含)moleculessuchasfattyacidsandtheirderivatives(includingtri,di,andmonoglycerides(單甘酯)andphospholipids),aswellasothersterolcontainingmetabolites(代謝物)suchascholesterol(膽固醇).Althoughhumansandothermammalsusevariousbiosyntheticpathwaystobothbreakdownandsynthesize(合成)lipids,someessentiallipidscannotbemadethiswayandmustbeobtainedfromthediet.21Categoriesoflipids脂質的類別211Fattyacyls脂肪酰類Fattyacyls,agenerictermfordescribingfattyacids,their脂肪酰類的定義。

conjugates(軛合物)andderivatives(衍生品),areadiverse(多樣化的)groupofmoleculessynthesized(合成)bychainelongation(延伸)ofanacetylCoA(乙酰輔酶A)primer(引物)withmalonylCoA(丙二酰輔酶A)ormethylmalonylCoAgroupsinaprocesscalledfattyacidsynthesis.Theyaremadeofahydrocarbon(碳氫化合物)chainthatterminates(終止)withacarboxylic(羧基的)acidgroup;thisarrangementconfers(賦予)themoleculewithapolar,hydrophilicend(親水末端),andanonpolar(非極性的),hydrophobicend(疏水末端)thatisinsolubleinwater.Thefattyacidstructureisoneofthemostfundamental023生物化學簡明雙語教程脂肪酸是生物脂質最基categoriesofbiologicallipids,andiscommonlyusedasa本的結構,常作為結構更buildingblockofmorestructurallycomplexlipids.Thecarbon複雜的脂質的組成單元。

chain,typicallybetween4to24carbonslong,maybesaturated(飽和)orunsaturated,andmaybeattachedtofunctionalgroupscontainingoxygen,halogens(鹵素),nitrogen(氮)andsulfur(硫).Whereadoublebondexists,thereisthepossibility順式雙鍵導致脂肪酸鏈ofeitheracisortransgeometricisomerism(幾何異構體),彎曲,當鏈中有更多的雙whichsignificantlyaffectsthemoleculesmolecular鍵時,效果會更明顯,這相configuration(分子構型).Cisdoublebondscausethefattyacid應地又在細胞膜的結構chaintobend,aneffectthatismorepronouncedthemore和功能中起著重要的作doublebondsthereareinachain.Thisinturnplaysan用。大多數天然存在的脂imortantroleinthestructureandfunctionofcellmembranes.肪酸是順式構型,而反式p,形式存在於一些天然的Mostnaturallyoccurringfattyacidsareofthecisconfiguration和部分氫化的脂肪和althoughthetransformdoesexistinsomenaturalandpartially油中。hydrogenatedfatsandoils.Examplesofbiologicallyimportantfattyacidsaretheeicosanoids(二十烷類),derivedprimarilyfromarachidonicacid(花生四烯酸)andeicosapentaenoic(二十碳五烯)acid,whichincludeprostaglandins(前列腺素),leukotrienes(白細胞三烯),andthromboxanes(血栓烷).212Glycerolipids甘油酯甘油三酯的組成。Glycerolipidsarecomposedmainlyofmono,diandtrisubstitutedglycerols(甘油),themostwellknownbeingthefattyacidtriesters(三酯)ofglycerol(triacylglycerols(甘油三因為擔負著食物儲存作酯)),alsoknownastriglycerides.Inthesecompounds,the用,動物組織中大量的儲threehydroxylgroupsofglycerolareeachesterified,usuallyby存脂肪都屬於甘油酯。甘differentfattyacids.Becausetheyfunctionasafoodstore,油三酯的酯鍵的水解以theselipidscomprisethebulkofstoragefatinanimaltissues.及從脂肪組織釋放出甘Thehydrolysisoftheesterbondsoftriacylglycerolsandthe油和脂肪酸被稱為脂肪動員。releaseofglycerolandfattyacidsfromadiposetissueiscalledfatmobilization(脂肪動員).213Glycerophospholipids甘油磷脂磷脂的分布與重要性。Glycerophospholipids,alsoreferredtoasphospholipids(磷024PartIStructuralBiochemistry結構生物化學脂),areubiquitous(普遍存在)innatureandarekeycomponentsofthelipidbilayer(脂雙層)ofcells,aswellasbeinginvolvedinmetabolismandcellsignaling.Neuraltissue(神經組織)(includingthebrain)containsrelativelyhighamountsofglycerophospholipids,andalterations(改變)intheircompositionhasbeenimplicatedinvariousneurologicaldisorders(神經障礙或紊亂).Phosphatidylethanolamine(磷脂酰乙醇胺)Examplesofglycerophospholipidsfoundinbiological生物膜磷脂酰膽堿、磷脂membranes(膜)arephosphatidylcholine(磷脂酰膽堿)(also酰乙醇胺和磷脂酰絲氨酸除了作為細胞膜的主knownasPC,GPChoorlecithin),phosphatidylethanolamine要成分以及胞內和胞間(PEorGPEtn)andphosphatidylserine(磷脂酰絲氨酸)(PSor蛋白的結合位點,在真核GPSer).Inadditiontoservingasaprimarycomponent(組件)細胞中的一些甘油磷脂,(細胞)ofcellularmembranesandbindingsitesforintraand如磷脂酰肌醇和磷脂酸,intercellularproteins,someglycerophospholipidsineukaryotic或者作為前體,或者本身cells,suchasphosphatidylinositols(磷脂酰肌醇)and作為膜源第二信使。

phosphatidicacidsareeitherprecursorsof,orarethemselves,membranederivedsecondmessengers.214Sphingolipids鞘脂Sphingolipidsareacomplexfamilyofcompoundsthatshareacommonstructuralfeature,asphingoidbasebackbonethatissynthesized(合成)denovo(從頭)fromtheaminoacidserine鞘脂類化合物的結構及(絲氨酸)andalongchainfattyacylCoA,thenconverted(轉來源。

換)intoceramides(神經酰胺),phosphosphingolipids(磷酸化鞘脂),glycosphingolipids(鞘糖脂)andothercompounds.Themajorsphingoidbase(類鞘氨醇堿)ofmammals(哺乳動物)iscommonlyreferredtoassphingosine.Ceramides(神經酰胺)025生物化學簡明雙語教程(Nacylsphingoidbases)areamajorsubclassofsphingoidbasederivativeswithanamidelinkedfattyacid.Thefattyacidsaretypicallysaturatedormonounsaturatedwithchainlengthsfrom16to26carbonatoms.Theglycosphingolipidsareadiversefamilyofmoleculescomposedofoneormoresugarresidueslinkedviaaglycosidicbond(糖苷鍵)tothesphingoidbase(鞘氨醇堿).Examplesofthesearethesimpleandcomplexglycosphingolipidssuchascerebrosides(腦苷脂)andgangliosides(神經節苷脂).Sphingomyelin(鞘磷脂).215Sterollipids固醇脂固醇脂種類的特點及生Sterollipids,suchascholesterol(膽固醇)anditsderivatives,物學功能。areanimportantcomponentofmembranelipids,alongwiththeglycerophospholipidsandsphingomyelins.Thesteroids(類固醇),allderivedfromthesamefusedfourringcorestructure,havedifferentbiologicalrolesashormones(激素)andsignalingmolecules所有類固醇都是從同一稠(信號分子).Theeighteencarbon(C18)steroidsincludethe合四環核心結構衍生而estrogenfamily(雌性激素家族)whereastheC19steroidscomprise來,各有其生物學功能,如theandrogens(雄性激素)suchastestosterone(睾酮)and作為激素和信號分子。

androsterone(雄甾酮).TheC21subclass(子類)includestheprogestogens(孕激素)aswellastheglucocorticoids(糖皮質激素)andmineralocorticoids(鹽皮質激素).216Saccharolipids糖脂Saccharolipidsdescribecompoundsinwhichfattyacidsare糖脂化合物是由脂肪酸linkeddirectlytoasugarbackbone,formingstructuresthatare直接連接糖骨架形成的。compatiblewith(一致)membranebilayers.Inthesaccharolipids,a它具有與膜脂雙層一致monosaccharide(單糖)substitutes(取代)fortheglycerol的結構。

backbonepresentinglycerolipidsandglycerophospholipids(甘油磷脂).Themostfamiliarsaccharolipidsaretheacylated026PartIStructuralBiochemistry結構生物化學glucosamine(酰化氨基葡萄糖)precursorsoftheLipidAcomponentofthelipopolysaccharides(脂多糖)inGramnegativebacteria.糖脂Kdo2LipidA的結構。

StructureofthesaccharolipidKdo2LipidA.TypicallipidAmoleculesaredisaccharidesofglucosamine,whicharederivatizedwithasmanyassevenfattyacylchains.TheminimallipopolysacchariderequiredforgrowthinE.col(大腸杆菌)isKdo2LipidA,ahexaacylated(六酰化)disaccharideofglucosaminethatisglycosylated(糖基化的)withtwo3deoxy(脫氧)Dmannooctulosonic(辛酮糖)acid(Kdo)residues(殘基).217Polyketides聚酮化合物Polyketidesaresynthesizedbypolymerization(聚合)of聚酮化合物的合成來源acetyl(乙酰基)andpropionyl(丙酰)subunitsbyclassic及其應用。

enzymesaswellasiterative(迭代)andmultimodular(多模塊化)enzymesthatsharemechanisticfeatures(機理特征)withthefattyacidsynthases.Theycomprisealargenumberofsecondarymetabolites(次級代謝產物)andnaturalproductsfromanimal,plant,bacterial,fungal(真菌)andmarine(海洋027生物化學簡明雙語教程的)sources,andhavegreatstructuraldiversity(結構多樣).Manypolyketidesarecyclicmolecules(環狀分子)whosebackbonesareoftenfurthermodifiedbyglycosylation(糖基化),methylation(甲基化),hydroxylation(羥基化),oxidation,and/orotherprocesses.Manycommonlyusedantimicrobial,antiparasitic(抗寄生蟲),andanticanceragentsarepolyketidesorpolyketidederivatives,suchaserythromycins(紅黴素),tetracyclines(四環素),avermectins(阿維菌素),andantitumorepothilones(埃坡黴素抗癌藥物).22Biologicalfunctions生物功能221Membranes細胞膜甘油磷脂是生物膜,如質Eukaryoticcells(真核細胞)arecompartmentalized(劃分)into膜和細胞器內膜的主要membraneboundorganelles(膜結合細胞器)whichcarryout結構組分。動物細胞中,differentbiologicalfunctions.Theglycerophospholipids(甘油磷脂)質膜把胞內組分與胞外arethemainstructuralcomponentofbiologicalmembranes,suchas環境進行了物理分隔。甘thecellularplasmamembrane(質膜)andtheintracellular油磷脂是兩親分子(同時;含疏水性和親水性結構),membranesoforganellesinanimalcellstheplasmamembrane()其甘油核心結構以酯鍵physicallyseparates分離theintracellularcomponentsfromthe連接兩個脂肪酸衍生物extracellular(胞外)environment.Theglycerophospholipidsare“尾巴”,並以酯鍵連接一amphipathicmolecules(兩親分子)(containingbothhydrophobicand個磷酸“頭部”。hydrophilicregions)thatcontainaglycerolcorelinkedtotwofattyacidderived“tails”byesterlinkagesandtoone“head”groupbyaphosphateesterlinkage.Whileglycerophospholipidsarethemajorcomponentofbiologicalmembranes,othernonglyceridelipidcomponentssuchassphingomyelin(鞘磷脂)andsterols(mainlycholesterolinanimalcellmembranes)arealsofoundinbiologicalmembranes.Lipidbilayers(磷脂雙分子層)havebeenfoundtoexhibithighlevelsofbirefringence(雙折射)whichcanbeusedtoprobethedegreeoforder(有序度)(ordisruption)withinthebilayerusingtechniquessuchasdualpolarisationinterferometry(雙偏振幹涉).Abiologicalmembraneisaformoflipidbilayer.The028PartIStructuralBiochemistry結構生物化學formationoflipidbilayersisanenergeticallypreferredprocess(能量優先過程)whentheglycerophospholipids(甘油磷脂)describedaboveareinanaqueousenvironment(水相環境).Inanaqueoussystem,thepolarheadsoflipidsalign(排列)在水體係中,脂質的極性towardsthepolar,aqueousenvironment,whilethehydrophobic頭部向著極性的水相環tailsminimizetheircontactwithwaterandtendtocluster境排列,而疏水的尾部則盡量少接觸水而成團簇,together,formingavesicle;dependingontheconcentration(濃形成囊泡。根據脂質濃度)ofthelipid,thisbiophysicalinteractionmayresultinthe度,這種生物物理作用可formationofmicelles(膠束),liosomes,orliidbilaers.ppy形成膠束,脂質體或脂雙()Otheraggregations聚合arealsoobservedandformpartof層。疏水效應解釋。當某thepolymorphism(多態性)ofamphiphile(lipid)behavior(兩親種極性環境中溶解了一行為).Micellesandbilayersforminthepolarmediumbya種親脂性或兩親性物質,processknownasthehydrophobiceffect(疏水效應).When極性分子(如水溶液中的dissolvingalipophilicoramphiphilicsubstanceinapolar水)會在溶解的脂質物周environment,thepolarmolecules(i.e.,waterinanaqueous圍更有序排列,因為極性分子無法與兩親分子的solution)becomemoreorderedaroundthedissolvedlipophilic親脂區形成氫鍵。因此,substance,sincethepolarmoleculescannotformhydrogen在水環境中,水分子形成bondstothelipophilicareasoftheamphiphile.Soinanaqueous一個有序的“籠”包圍著溶,“”environmentthewatermoleculesformanorderedclathrate解在其中的親脂性分子。

cagearoundthedissolvedlipophilicmolecule.磷脂的自組織:球形脂質體,膠束和脂雙層。

Selforganizationofphospholipids:asphericalliposome,amicelleandalipidbilayer.029生物化學簡明雙語教程222Energystorage能量儲存Triacylglycerols(甘油三酯),storedinadiposetissue,areamajorformofenergystorageinanimals.Theadipocyte(脂肪細脂肪酸的完全氧化能提胞),orfatcell,isdesignedforcontinuoussynthesisand供高達約9千卡/克的熱breakdownoftriacylglycerols,withbreakdowncontrolled量,相比之下,糖和蛋白質mainlybytheactivationofhormonesensitive(激素敏感)分解提供4千卡/克的熱enzymelipase.Thecompleteoxidationoffattyacidsprovides量。候鳥為了進行長距離highcaloriccontent,about9kcal/g,comparedwith4kcal/g無攝食的飛行,必須要使forthebreakdownofcarbohdratesandroteins.Mirator用甘油三酯儲存的能量ypgy()幫助飛行。birds候鳥thatmustflylongdistanceswithouteatingusestoredenergyoftriacylglycerolstofueltheirflights.223Signaling信號傳導近年來,有確鑿的證據表Inrecentyears,evidencehasemergedshowingthatlipid明脂質信號傳導是細胞signalingisavitalpartofthecellsignaling.Lipidsignalingmay信號傳導的一個重要部occurviaactivationofGproteincoupled(G蛋白偶聯)or分。

nuclearreceptors(核受體),andmembersofseveraldifferentlipidcategorieshavebeenidentifiedassignalingmoleculesandcellularmessengers(細胞信使).Theseincludesphingosine1phosphate(鞘氨醇1磷酸),asphingolipidderivedfromceramide(神經酰胺)thatisapotentmessengermoleculeinvolvedinregulatingcalciummobilization(調控鈣動員),cellgrowth,andapoptosis(細胞凋亡);diacylglycerol(甘油二酯)(DAG)andthephosphatidylinositolphosphates(磷脂酰肌醇磷酸鹽,PIPs),involvedincalciummediatedactivationofproteinkinaseC(蛋白激酶C);theprostaglandins(前列腺素),whichareonetypeoffattyacidderivedeicosanoid(類花生酸)involvedininflammation(炎症)andimmunity(免疫);thesteroidhormonessuchasestrogen(雌激素),testosterone(睾酮)andcortisol(皮質醇),whichmodulate(調製)ahostoffunctionssuchasreproduction,metabolismandbloodpressure;andtheoxysterols(氧化型膽固醇)suchas25hydroxycholesterol(25羥基膽固醇)thatareliverXreceptoragonists(受體激動劑).030PartIStructuralBiochemistry結構生物化學23Metabolicprofiles代謝概況Themajordietarylipidsforhumansandotheranimalsareanimalandplanttriglycerides,sterols(固醇類),andmembranephospholipids.Theprocessoflipidmetabolismsynthesizesanddegradesthelipidstoresandproducesthestructuralandfunctionallipidscharacteristicofindividualtissues.231Biosynthesis生物合成Inanimals,whenthereisanoversupplyofdietary甘油三酯的合成途徑。

carbohydrate,theexcesscarbohydrateisconvertedtotriacylglycerol.ThisinvolvesthesynthesisoffattyacidsfromacetylCoA(乙酰輔酶A)andtheesterificationoffattyacidsintheproductionoftriacylglycerol,aprocesscalledlipogenesis(脂肪生成).Fattyacidsaremadebyfattyacidsynthases(脂肪酸合酶)thatpolymerizeandthenreduceacetylCoAunits.Theacylchainsinthefattyacidsareextendedbyacycleofreactionsthataddtheacetylgroup,reduceittoanalcohol,dehydrate(脫水)ittoanalkenegroup(烯烴)andthenreduceitagaintoanalkanegroup(烷烴).Theenzymesoffattyacidbiosynthesisaredividedintotwo參與脂肪酸生物合成的groups,inanimalsandfungi(真菌)allthesefattyacidsynthase酶分為兩種類型。

reactionsarecarriedoutbyasinglemultifunctionalprotein(多功能蛋白),whileinplantplastids(質粒體)andbacteriaseparateenzymesperformeachstepinthepathway(通路).Thefattyacidsmaybesubsequentlyconvertedtotriacylglycerolsthatarepackagedinlipoproteinsandsecreted(分泌)fromtheliver.Thesynthesisofunsaturatedfattyacidsinvolvesa不飽和脂肪酸生物合成desaturationreaction(脫氫反應),wherebyadoublebondis過程。