生物專業(yè)英語(yǔ)第三版蔣悟生編-課文翻譯

生物工程專業(yè)英語(yǔ)PAGEPAGE32InsidetheLivingCell:StructureandFunctionofInternalCellPartsCytoplasm:TheDynamic,MobileFactory細(xì)胞質(zhì)：動(dòng)力工廠Mostofthepropertiesweassociatewithlifearepropertiesofthecytoplasm.Muchofthemassofacellconsistsofthissemifluidsubstance,whichisboundedontheoutsidebytheplasmamembrane.Organellesaresuspendedwithinit,supportedbythefilamentousnetworkofthecytoskeleton.Dissolvedinthecytoplasmicfluidarenutrients,ions,solubleproteins,andothermaterialsneededforcellfunctioning.生命的大部分特征表現(xiàn)在細(xì)胞質(zhì)的特征上。細(xì)胞質(zhì)大部分由半流體物質(zhì)組成，并由細(xì)胞膜（原生質(zhì)膜）包被。細(xì)胞器懸浮在其中，并由絲狀的細(xì)胞骨架支撐。細(xì)胞質(zhì)中溶解了大量的營(yíng)養(yǎng)物質(zhì)，離子，可溶蛋白以及維持細(xì)胞生理需求的其它物質(zhì)。TheNucleus:InformationCentral（細(xì)胞核：信息中心）Theeukaryoticcellnucleusisthelargestorganelleandhousesthegeneticmaterial(DNA)onchromosomes.(Inprokaryotesthehereditarymaterialisfoundinthenucleoid.)Thenucleusalsocontainsoneortwoorganelles-thenucleoli-thatplayaroleincelldivision.Apore-perforatedsaccalledthenuclearenvelopeseparatesthenucleusanditscontentsfromthecytoplasm.Smallmoleculescanpassthroughthenuclearenvelope,butlargermoleculessuchasmRNAandribosomesmustenterandexitviathepores.真核細(xì)胞的細(xì)胞核是最大的細(xì)胞器，細(xì)胞核對(duì)染色體組有保護(hù)作用（原核細(xì)胞的遺傳物質(zhì)存在于擬核中）。細(xì)胞核含有一或二個(gè)核仁，核仁促進(jìn)細(xì)胞分裂。核膜貫穿許多小孔，小分子可以自由通過(guò)核膜，而象mRNA和核糖體等大分子必須通過(guò)核孔運(yùn)輸。Organelles:SpecializedWorkUnits（細(xì)胞器：特殊的功能單位）Alleukaryoticcellscontainmostofthevariouskindsoforganelles,andeachorganelleperformsaspecializedfunctioninthecell.Organellesdescribedinthissectionincluderibosomes,theendoplasmicreticulum,theGolgicomplex,vacuoles,lysosomes,mitochondria,andtheplastidsofplantcells.所有的真核細(xì)胞都含有多種細(xì)胞器，每個(gè)細(xì)胞器都有其特定功能。本節(jié)主要介紹核糖體，內(nèi)質(zhì)網(wǎng)，高爾基體系，液泡，溶酶體，線粒體和植物細(xì)胞中的質(zhì)體。Thenumberofribosomeswithinacellmayrangefromafewhundredtomanythousands.Thisquantityreflectsthefactthat,ribosomesarethesitesatwhichaminoacidsareassembledintoproteinsforexportorforuseincellprocesses.Acompleteribosomeiscomposedofonelargerandonesmallersubunit.DuringproteinsynthesisthetwosubunitsmovealongastrandofmRNA,"reading"thegeneticsequencecodedinitandtranslatingthatsequenceintoprotein.SeveralribosomesmaybecomeattachedtoasinglemRNAstrand;suchacombinationiscalledapolysome.Mostcellularproteinsaremanufacturedonribosomesinthecytoplasm.Exportableproteinsandmembraneproteinsareusuallymadeinassociationwiththeendoplasmicreticulum.核糖體的數(shù)量變化從幾百到幾千，核糖體是氨基酸組裝成蛋白質(zhì)的重要場(chǎng)所。完整的核糖體由大亞基和小亞基組成。核糖體沿著mRNA移動(dòng)并閱讀遺傳密碼，翻譯成蛋白質(zhì)。一條mRNA上可能有多個(gè)核糖體，稱多聚核糖體。大多數(shù)細(xì)胞蛋白是由細(xì)胞質(zhì)中核糖體生產(chǎn)。輸出蛋白和膜蛋白通常與內(nèi)質(zhì)網(wǎng)有關(guān)。Theendoplasmicreticulum,alacyarrayofmembranoussacs,tubules,andvesicles,maybeeitherrough(RER)orsmooth(SER).Bothtypesplayrolesinthesynthesisandtransportofproteins.TheRER,whichisstuddedwithpolysomes,alsoseemstobethesourceofthenuclearenvelopeafteracelldivides.內(nèi)質(zhì)網(wǎng)，帶有花邊的生物囊，有管狀，泡狀之分，以及光滑和粗糙面區(qū)別。兩種都與蛋白質(zhì)的合成和運(yùn)輸有關(guān)。粗糙內(nèi)質(zhì)網(wǎng)上分布許多核糖體，也可能提供細(xì)胞分裂后所需的細(xì)胞膜。SERlackspolysomes;itisactiveinthesynthesisoffatsandsteroidsandintheoxidationoftoxicsubstancesinthecell.Bothtypesofendoplasmicreticulumserveascompartmentswithinthecellwherespecificproductscanbeisolatedandsubsequentlyshuntedtoparticularareasinoroutsidethecell.光滑內(nèi)質(zhì)網(wǎng)上無(wú)核糖體，主要作用是脂肪和類固醇的合成以及細(xì)胞內(nèi)有毒物質(zhì)的氧化。兩種內(nèi)質(zhì)網(wǎng)合成的產(chǎn)物在其中進(jìn)行分流或運(yùn)輸?shù)郊?xì)胞外。Transportvesiclesmaycarryexportablemoleculesfromtheendoplasmicreticulumtoanothermembranousorganelle,theGolgicomplex.WithintheGolgicomplexmoleculesaremodifiedandpackagedforexportoutofthecellorfordeliveryelsewhereinthecytoplasm.運(yùn)輸小泡能夠?qū)⒖蛇\(yùn)輸分子從內(nèi)質(zhì)網(wǎng)運(yùn)輸?shù)礁郀柣鶑?fù)合體上。在高爾基復(fù)合體中修飾，包裝后輸出細(xì)胞或傳遞到細(xì)胞質(zhì)中的其他場(chǎng)所。Vacuolesincellsappeartobehollowsacsbutareactuallyfilledwithfluidandsolublemolecules.Themostprominentvacuolesappearinplantcellsandserveaswaterreservoirsandstoragesitesforsugarsandothermolecules.Vacuolesinanimalcellscarryoutphagocytosis(theintakeofparticulatematter)andpinocytosis(vacuolardrinking).細(xì)胞中的液泡好象是中空的，但實(shí)際上充滿了液體和可溶分子。最典型的液泡存在于植物細(xì)胞中，儲(chǔ)備水，糖以及其它分子。動(dòng)物中的液泡起吞噬和胞飲作用。Asubsetofvacuolesaretheorganellesknownaslysosomes,whichcontaindigestiveenzymes(packagedinlysosomesintheGolgicomplex)thatcanbreakdownmostbiologicalmacromolecules.Theyacttodigestfoodparticlesandtodegradedamagedcellparts.溶酶體是液泡亞單位，含有消化酶，降解大部分生物大分子。消化食物微粒和降解損傷的細(xì)胞殘片。Mitochondriaarethesitesofenergy-yieldingchemicalreactionsinallcells.Inaddition,plantcellscontainplastidsthatutilizelightenergytomanufacturecarbohydratesintheprocessofphotosynthesis.ItisonthelargesurfaceareaprovidedbytheinnercristaeofmitochondriathatATP-generatingenzymesarelocated.Mitochondriaareself-replicating,andprobablytheyaretheevolutionarydescendantsofwhatwereoncefree-livingprokaryotes.線粒體是細(xì)胞中化學(xué)產(chǎn)能的場(chǎng)所。另外，植物細(xì)胞中的質(zhì)體在光合作用中利用光能產(chǎn)生碳水化合物，線粒體內(nèi)嵴上提供了很大的表面積并分布著產(chǎn)ATP酶。線粒體自我復(fù)制，并且可能是自由生活的原核生物在進(jìn)化中形成的后代。Therearetwotypesofplastids:leucoplasts,whichlackpigmentsandserveasstoragesitesforstarch,proteins,andoils;andchromoplasts,whichcontainpigments.Themostimportantchromoplastsarechloroplasts-organellesthatcontainthechlorophyllusedinphotosynthesis.Theinternalstructureofchloroplastsincludesstacksofmembranescalledgrana,whichareembeddedinamatrixcalledthestroma.質(zhì)體有兩種類型：白色體，缺乏色素，是淀粉，蛋白質(zhì)和油的儲(chǔ)備場(chǎng)所；色質(zhì)體，含有色素。葉綠體是最重要的色質(zhì)體，含有與光合作用有關(guān)的葉綠素。葉綠體的內(nèi)部結(jié)構(gòu)是由多層膜形成的葉綠體基粒，其中包埋在基質(zhì)中的基粒稱子座。TheCytoskeleton（細(xì)胞骨架）Alleukaryoticcellshaveacytoskeleton,whichisaconvolutedlatticeworkoffilamentsandtubulesthatappearstofillallavailablespaceinthecellandprovidessupportforvariousotherorganelles.Alargeportionofthecytoskeletonconsistsofthreadlikemicrofilamentscomposedmainlyofthecontractileproteinactin.Theyareinvolvedinmanytypesofintracellularmovementsinplantandanimalcells.Asecondprotein,myosin,isinvolveinthecontractionofmusclecells.Anothermainstructuralcomponentofthecytoskeletonconsistsofmicrotubules,whicharecomposedoftheglobularproteintubulinandtogetheractasscaffoldingthatprovidesastablecellshape.Cytoskeletalintermediatefilamentsappeartoimparttensilestrengthtothecellcytoplasm.Mechanoenzymessuchasmyosin,dynein,andkinesininteractwiththecytoskeletalfilamentsandtubulestogenerateforcesthatcausemovements.所有的細(xì)胞都有細(xì)胞骨架，網(wǎng)絡(luò)結(jié)構(gòu)的纖絲充滿了它所能觸及的全部空間并且對(duì)細(xì)胞器提供支持作用。細(xì)胞骨架大部分由微絲組成，微絲主要由可收縮的肌動(dòng)蛋白組成。動(dòng)植物細(xì)胞的許多種類型細(xì)胞內(nèi)運(yùn)動(dòng)與肌動(dòng)蛋白有關(guān)。第二類蛋白是肌球蛋白，它與肌肉細(xì)胞的收縮有關(guān)。細(xì)胞骨架的另一個(gè)主要結(jié)構(gòu)成分是微管，由球狀的微管蛋白組成，象腳手架一般維持細(xì)胞的穩(wěn)定形態(tài)。細(xì)胞骨架的中間絲提供了細(xì)胞質(zhì)伸縮動(dòng)力。機(jī)械酶，例如，肌球蛋白，動(dòng)力蛋白，驅(qū)動(dòng)蛋白與微絲，微管相互作用產(chǎn)生動(dòng)力而引起細(xì)胞運(yùn)動(dòng)。CellularMovements（細(xì)胞運(yùn)動(dòng)Althoughthecytoskeletonprovidessomestability穩(wěn)固tocells,itsmicrotubules英[?maikr?u?tju:bju:l]andfilaments絲狀物andtheirassociatedproteinsenablecellstomovebycreeping爬行orgliding滑動(dòng).Suchmovementsrequireasolid固體的substratetowhichthecellcanadhere附著andcanbeguidedbythegeometryd?i??mitri]

幾何形狀ofthesurface.Somecellsalsoexhibit[iɡ?zibit]展覽chemotaxis,kem??t?ksis趨藥性theabilitytomovetowardorawayfromthesourceofadiffusing擴(kuò)散chemical.盡管細(xì)胞骨架提供了細(xì)胞的某些穩(wěn)定性，微絲，微管及相關(guān)蛋白能使細(xì)胞爬行或滑動(dòng)。這種運(yùn)動(dòng)需要固體基質(zhì)依托并通過(guò)表面幾何形狀的改變而運(yùn)動(dòng)。某些細(xì)胞具備趨藥性，即趨向或逃離擴(kuò)散開的化學(xué)源。Certaineukaryoticcellscanswimfreelyinliquidenvironments,propelledbywhiplikecilia[?sili?]纖毛orflagella英[fl??d?el?鞭毛.Bothciliaandflagellahavethesameinternalstructure:ninedoublets(pairsofmicrotubules)arearrangedinaringandextendthelengthoftheciliumorflagellum,andtwomoremicrotubulesrundownthecenterofthering.Everyciliumorflagellumgrowsonlyfromthecellsurfacewhereabasalbody基體islocated.Movementisbasedontheactivitiesoftinydynein動(dòng)力蛋白sidearmsthatextendfromoneofthemicrotubulesofeachdoublet成對(duì)的東西.某些真核細(xì)胞能在液體液體中自由運(yùn)動(dòng)，由纖毛或鞭毛推動(dòng)。纖毛和鞭毛具有同樣的內(nèi)部結(jié)構(gòu)：九個(gè)雙微管環(huán)形排列，縱向延伸，環(huán)中心是兩個(gè)或以上微管組成。纖毛或鞭毛從細(xì)胞表面的基體出生長(zhǎng)，雙微管的動(dòng)力蛋白臂從一側(cè)延伸到另一側(cè)而引起運(yùn)動(dòng)。 Nutrients,proteins,andothermaterialswithinmostplantcellsaremovedaboutviacytoplasmicstreaming.Theprocessoccursasmyosin?mai?usin肌凝蛋白proteinsattachedtoorganelles細(xì)胞器,小器官pushagainstmicrofilamentsarrayed[??rei]展示throughoutthecell.Microfilamentsandmicrotubulesareresponsibleforalmostallmajorcytoplasmicmovements.Duringcelldivision,microtubulesofthespindleassembled集合,收集fromtubutinsubunitsnearorganellescalledcentriolesmovethechromosomes.大部分植物細(xì)胞的營(yíng)養(yǎng)，蛋白質(zhì)和其它物質(zhì)由細(xì)胞質(zhì)流運(yùn)輸。這個(gè)過(guò)程是由于依附在細(xì)胞器上的肌球蛋白反推排列在細(xì)胞周圍的微絲形成的。絕大部分細(xì)胞質(zhì)運(yùn)動(dòng)由微絲和微管完成。在細(xì)胞分裂期間，中心粒周圍的由微管蛋白亞基裝配形成的紡錘體微管移向染色體。

Glossarycytoplasm（細(xì)）胞質(zhì)Thelivingcontentsofacellboundedexternallybytheplasmalemma,includinganaqueousgroundsubstance(hyaloplasm,cellsap,orcellmatrix)containingorganellesandvariousinclusionsbutexcludingthenucleusandvisiblevacuoles.cytoskeleton細(xì)胞骨架Ofeukaryoticcells,aninternal"skeleton".Itsmicrotubulesandothercomponentsstructurallysupportthecell,organizeandmoveitsinteftialcomponents.Thecytoskeletonalsohelpsfree-livingcellsmovethroughtheirenvironment.nucleus細(xì)胞核，核(復(fù)數(shù)nuclei)Theorganelleoftheeukaryotecellthatcontainsthechromosomesandhenceultimatelycontrolscellularactivityandinheritancethroughtheactivityofthegeneticmaterial,DNAchromosome染色體ADNA-histonethreadresidinginthenucleusofacell.Eachchromosomepossessestwotelomeresandacentromere,andsomecontainanucleolusorganizer.RNAproteinsareinvariablyassociatedwiththechromosome.nucleoid擬核，類核，核質(zhì)體TheDNA-containingareaofaprokaryotecell,analogoustotheeukaryotenucleusbutnotmembranebounded.nucleoli核仁(單數(shù)nucleolus)Nuclearstructurescomposedofcompletedorpartiallycompletedribosomesandthespecificpartsofchromosomesthatcontaintheinfon-nationfortheirconstruction.nuclearenvelope核膜，核被膜Adoublemembrane(twolipidbilayersandassociatedproteins)thatistheoutermostportionofacellnucleus.ribosome核糖體Smallstructurescomposedoftwoproteinandribonucleicacidsubunitsinvolvedintheassemblyofproteinsfromaminoacids.polysome多核糖體Ofproteinsynthesis,severalribosomesalltranslatingthesamemessengerRNAmolecule,oneaftertheother.endoplasmicreticulum內(nèi)質(zhì)網(wǎng)Foldedmembranesandtubesthroughouttheeukaryoticcellthatprovidealargesurfaceuponwhichchemicalactivitiestakeplace.Golgicomplex高爾基復(fù)合體Astackofflattened,smooth,membranoussacs;thesiteofsynthesisandpackagingofcertainmoleculesineukaryoticcells.vacuole液泡Storagecontainerwithinthecytoplasmofacellhavingasurroundingmembrane.phagocytosis吞噬作用Theprocessbywhichthecellwrapsaroundaparticleandengulfsit.pinocytosis胞飲作用Theprocessbywhichacellengulfssomemoleculesdissolvedinwaterlysosome溶酶體Aspecializedorganellethatholdsamixtureofhydrolyticenzymes.mitochondrion線粒體(復(fù)數(shù)mitochondria)Amembranousorganelleresemblingasmallbagwithalargerbagresemblingasmallbagwithalargerbaginsidethatisfoldedbackonitself;servesasthesiteofaerobiccellularrespiration.plastid質(zhì)體Anorganellepresentinallplantsexceptbacteria,blue-greenalgae,andfungi;itisenclosedbytwomembranes(theenvelope)andhasvariousfunctionschloroplast葉綠體Aplastidinwhichphotosynthesisiscarriedout.Chloroplastsoccurinallphotosyntheticorganismsexceptphotosyntheticbacteriablue-greenalgae.stroma基質(zhì)，子座（復(fù)數(shù)stromata）Regionwithinachloroplastthathasnochlorophyll.microfilament微絲，纖絲Long,fiberlikestructuresmadeofproteinandfoundincells,oftenincloseassociationwiththemicrotubules;providestructuralsupportandenablemovement.actin肌動(dòng)蛋白Aglobularcontractileprotein.Inmusclecells,actininteractswithanotherprotein,myosin,tobringaboutcontraction.myosin['maiesin]肌球蛋白Aproteinthat,withactin,constitutestheprincipalelementofthecontractileapparatusofmuscle.microtubute微管Small,hollowtubesofproteinthatfunctionthroughoutthecytoplasmtoprovidestructuralsupportandenablemovement.tubulin微管蛋白Aproteinthatisthemajorconstituentofmicrotubules.dynein動(dòng)力蛋白，動(dòng)素AgroupofatleastfourdistinctproteinsfoundintheflagellaandmicrotubulesofeukaryoticcellsandpossessingATPaseactivity.chemotaxis趨化性Alocomotorymovementofanorganismorcellinresponseto,anddirectedby,andirectionalstimulus.cilia纖毛Numerousshort,hairlikestructuresprojectingfromthecellsurfacethatenablelocomotion.flagella鞭毛(單數(shù)flagellum)Long,hairlikestructuresprojectingfromthecellsurfacethatenablelocomotion.basalbody基體Abodyidenticalinstructuretoacentriole,foundalwaysatthebaseofaciliumoreukaryoteflagellum. centriole中心粒Anorganellelocatedclosetothenucleusinmostanimalandlowerplantcellsbutabsentfromprokaryotesandhigherplants.PhotosynthesisPhotosynthesisoccursonlyinthechlorophyllchlorophyll葉綠素-containingcellsofgreenplants,algae藻,andcertainprotists原生生物andbacteria.Overall,itisaprocessthatconvertslightenergyintochemicalenergythatisstoredinthemolecularbonds.Fromthepointofviewofchemistryandenergetics,itistheoppositeofcellularrespiration.Whereas然而cellular細(xì)胞的respiration呼吸ishighlyexergonic吸收能量的andreleasesenergy,photosynthesis光合作用requiresenergyandishighlyendergonic.光合作用只發(fā)生在含有葉綠素的綠色植物細(xì)胞，海藻，某些原生動(dòng)物和細(xì)菌之中?？傮w來(lái)說(shuō)，這是一個(gè)將光能轉(zhuǎn)化成化學(xué)能，并將能量貯存在分子鍵中，從化學(xué)和動(dòng)能學(xué)角度來(lái)看，它是細(xì)胞呼吸作用的對(duì)立面。細(xì)胞呼吸作用是高度放能的，光合作用是需要能量并高吸能的過(guò)程。PhotosynthesisstartswithCO2andH2Oasrawmaterialsandproceedsthroughtwosetsofpartialreactions.Inthefirstset,calledthelight-dependentreactions,watermoleculesaresplit裂開(oxidized),02isreleased,andATPandNADPHareformed.Thesereactionsmusttakeplaceinthepresenceof在面前l(fā)ightenergy.Inthesecondset,calledlight-independentreactions,CO2isreduced(viatheadditionofHatoms)tocarbohydrate.ThesechemicaleventsrelyontheelectroncarrierNADPHandATPgeneratedbythefirstsetofreactions.光合作用以二氧化碳和水為原材料并經(jīng)歷兩步化學(xué)反應(yīng)。第一步，稱光反應(yīng)，水分子分解，氧分子釋放，ATP和NADPH形成。此反應(yīng)需要光能的存在。第二步，稱暗反應(yīng)，二氧化碳被還原成碳水化合物，這步反應(yīng)依賴電子載體NADPH以及第一步反應(yīng)產(chǎn)生的ATP。Bothsetsofreactionstakeplaceinchloroplasts.Mostoftheenzymesandpigments色素forthelightdependentreactionsareembedded深入的內(nèi)含的inthethylakoid類囊體membrane膜隔膜ofchloroplasts葉綠體.Thedarkreactionstakeplaceinthestroma.基質(zhì)兩步反應(yīng)都發(fā)生在葉綠體中。光反應(yīng)需要的大部分酶和色素包埋在葉綠體的類囊體膜上。暗反應(yīng)發(fā)生在基質(zhì)中。HowLightEnergyReachesPhotosyntheticCells（光合細(xì)胞如何吸收光能的）Theenergyinlightphotonsinthevisiblepartofthespectrumcanbecapturedbybiologicalmoleculestodoconstructivework.Thepigmentchlorophyllinplantcellsabsorbsphotonswithinaparticularabsorptionspectrumsstatementoftheamountoflightabsorbedbychlorophyllatdifferentwavelengths.Whenlightisabsorbeditaltersthearrangementofelectronsintheabsorbingmolecule.Theaddedenergyofthephotonbooststheenergyconditionofthemoleculefromastablestatetoaless-stableexcitedstate.Duringthelight-dependentreactionsofphotosynthesis,astheabsorbingmoleculereturnstothegroundstate,the"excess"excitationenergyistransmittedtoothermoleculesandstoredaschemicalenergy.生物分子能捕獲可見光譜中的光能。植物細(xì)胞中葉綠素在不同光波下吸收部分吸收光譜。在吸收分子中，光的作用使分子中的電子發(fā)生重排。光子的能量激活了分子的能量狀態(tài)，使其從穩(wěn)定態(tài)進(jìn)入不穩(wěn)定的激活態(tài)。Allphotosyntheticorganismscontainvariousclassesofchlorophyllsandoneormorecarotenoid(accessory)pigmentsthatalsocontributetophotosynthesis.Groupsofpigmentmoleculescalledantennacomplexesarepresentonthylakoids.Lightstrikinganyoneofthepigmentmoleculesisfunneledtoaspecialchlorophyllamolecule,termedareaction-centerchlorophyll,whichdirectlyparticipatesinphotosynthesis.Mostphotosyntheticorganismspossesstwotypesofreaction-centerchlorophylls,P680andP700,eachassociatedwithanelectronacceptormoleculeandanelectrondonor.TheseaggregationsareknownrespectivelyasphotosystemⅠ(P700)andphotosystemⅡ(P680).所有的光合作用生物含有不同等級(jí)的葉綠素和一個(gè)或多個(gè)類胡蘿卜素（光合作用的輔助色素）。稱作天線復(fù)合體的色素分子群存在于類囊體中。激活色素分子的光能進(jìn)入葉綠素反應(yīng)中心，其直接參與光合作用。大部分光反應(yīng)細(xì)胞器擁有兩套反應(yīng)中心，P680和P700，每個(gè)光系統(tǒng)都含有一個(gè)電子受體和電子供體。這些集合體就是大家熟識(shí)的光合系統(tǒng)Ⅰ和光合系統(tǒng)Ⅱ。TheLight-DependentReaction:ConvertingSolarEnergyintoChemical-BondEnergy光反應(yīng)：光能轉(zhuǎn)化成化學(xué)鍵能Thephotosystemsofthelight-dependentreactionsareresponsibleforthepackagingoflightenergyinthechemicalcompoundsATPandNADPH.ThispackagingtakesplacethroughaseriesofoxidationreductionreactionssetinmotionwhenlightstrikestheP680reactioncenterinphotosystemⅡ.Inthisinitialeventwatermoleculesarecleaved,oxygenisreleased,andelectronsaredonated.Theseelectronsareacceptedfirstbyplastoquinoneandthenbyaseriesofcarriersastheydescendanelectrontransportchain.Foreachfourelectronsthatpassdownthechain,twoATPsareformed.ThelastacceptorinthechainistheP700reactioncenterofphotosystemⅠ.Atthispointincomingphotonsboosttheenergyoftheelectrons,andtheyareacceptedbyferredoxin.Ferredoxinisthenreoxidized,andthecoenzymeNADP+isreducedtotheNADPH.TheATPgeneratedpreviouslyandtheNADPHthentakepartinthelightindependentreactions.光反應(yīng)的光系統(tǒng)將光能轉(zhuǎn)化成化學(xué)復(fù)合物ATP和NADPH。當(dāng)光激活光系統(tǒng)Ⅱ的光反應(yīng)中心時(shí)，通過(guò)一系列的氧化還原反應(yīng)實(shí)現(xiàn)能量的傳遞。反應(yīng)開始時(shí)，水被分解，氧被釋放并提供電子。電子首先傳遞給質(zhì)體醌，然后通過(guò)一系列載體形成的電子傳遞鏈。每傳遞4個(gè)電子，形成2個(gè)ATP。最后一個(gè)受體存在于光反應(yīng)系統(tǒng)Ⅰ的反應(yīng)中心里。此處光子激活電子，電子傳遞給鐵氧還蛋白。鐵氧還蛋白再氧化，并且輔酶NADP+還原成NADPH。早期產(chǎn)生的ATP和NADPH進(jìn)入暗反應(yīng)。TheproductionofATPfromthetransportofelectronsexcitedbylightenergydownanelectrontransportchainistermedphotophosphorylation.Theone-wayflowofelectronsthroughphotosystemsIIandIiscallednoncyclicphotophosphorylation;plantsalsoderiveadditionalATPthroughcyclicphotophosphorylation,inwhichsomeelectronsareshuntedbackthroughtheelectrontransportchainbetweenphotosystemsⅡandⅠ.由電子傳遞鏈偶連產(chǎn)生ATP的過(guò)程稱為光合磷酸化。通過(guò)光合系統(tǒng)Ⅱ流經(jīng)光合系統(tǒng)Ⅰ的電子路徑稱非循環(huán)式光合磷酸化；植物通過(guò)循環(huán)式光合磷酸化獲得額外的ATP，一些電子在光合系統(tǒng)Ⅰ和Ⅱ之間的電子傳遞鏈中回流。TheLight-IndependentReactions:BuildingCarbohydrates暗反應(yīng)：碳水化合物的形成Inthelight-independentreactionsofphotosynthesis,whicharedrivenbyATPandNADPH,C02isconvertedtocarbohydrate.ThereactionsarealsoknownastheCalvin-Bensoncycle.AtmosphericCO2,isfixedasitreactswithribulosebiphosphate(RuBP),areactionthatiscatalyzedbytheenzymeribulosebiphosphatecarboxylase.ThereductionOfC02tocarbohydrate(fructosediphosphate)iscompletedviaseveralmorestepsofthecycle.Finally,RUBPisregeneratedsothatthecyclemaycontinue.由ATP和NADPH驅(qū)動(dòng)的暗反應(yīng)中，二氧化碳轉(zhuǎn)化成碳水化合物。即卡爾文循環(huán)。二磷酸核酮糖固定二氧化碳，由二磷酸核酮糖羧化酶催化。Oxygen:AnInhibitorofphotosynthesis（氧：光合作用的抑制因子）Highlevelsofoxygeninplantcellscandisruptphotosynthesisandcanalsocausephotorespiration-aninefficientfunofthedarkreactionsinwhich02isfixedratherthanC02andnocarbohydrateisproduced.ReprievefromPhotorespiration:TheC4PathwayMostplantsareC3plants;theyexperiencedecreasedcarbohydrateproductionunderhot,dryconditionsasaresultoftheeffectsofphotorespiration.AmongC4plants,however,specialleafanatomyandauniquebiochemicalpathwayenabletheplanttothriveinandconditions.ThusC4plantslessenphotorespirationbycarryingoutphotosynthesisonlyincellsthatareinsulatedfromhighlevelsofCO2.Theyalsopossessanovelmechanismforcarbonfixation.大部分植物是碳3植物，在高溫干旱條件下，由于光呼吸作用而使碳水化合物的合成降低。而在大多數(shù)的碳4植物中，由于葉脈的特殊構(gòu)造和獨(dú)特的化學(xué)路徑使植物依然很茂盛。這是碳固定的一個(gè)新機(jī)制。

課后作業(yè)：第一篇閱讀材料答案：1B,2A,3A,4D,5C,6cGlossarlight-dependentreactions光反應(yīng)-Thefirststageinphotosynthesis,drivenbylightenergy.Electronsthattrapthesun'senergypasstheenergytohigh-energycarrierssuchasATPorNADPH,whereitisstoredinchemicalbonds.light-independentreactions暗反應(yīng)Thesecondstageofphotosynthesis,alsocalledtheCalvin-Bensoncycle,whichdoesnotrequirelight.Duringthesixstepsofthecycle,carbonisfixedandcarbohydratesareformed.chloroplast葉綠體Aplastidinwhichphotosynthesisiscarriedout.Chloroplastsoccurinallphotosyntheticorganismsexceptphotosyntheticbacteriaandblue-greenalgae.absorptionspectrum吸收光譜，吸收譜Thespectrumobtainedwhenradiation(light,ultravioletradiation,etc.)fromasourcegivingacontinuousspectrumispassedthroughasubstance.Calvin-Bensoncycle卡爾文·本森循環(huán)Cyclicreactionsthatarethe"synthesis"partofthelight-independentreactionsofphotosynthesis.Inlandplants,RUBP,orsomeothercompoundtowhichcarbonhasbeenaffixed,undergoesrearrangementsthatleadtoformationofasugarphosphateandtoregenerationoftheRUBP.ThecyclerunsonATPandNADPHfromlight-dependentreactions.carotenoid類胡蘿卜素Light-sensitive,accessorypigmentsthattransferabsorbedenergytochlorophylls.Theyabsorbvioletandbluewave-lengthsbuttransmitred,orange,andyellow.chlorophyll葉綠素Thegreensubstanceofplantsbywhichphotosynthesisisaccomplished;itisusuallylocalizedinintracellularorganellescalledchloroplasts.cyclicphotophosphorylation環(huán)形光合磷酸化（作用）Cyclicphotophosphorylationiscoupledtocyclicelectronflow,inwhichATPistheonlyproduct.C3plant三碳植物Aplantinwhichthelight-independentreactionsofphotosynthesisstartwithathreecarboncompound.MostplantsareC3plants.C4plant四碳植物Aplantsuchascorninwhichthelightindependentreactionsofphotosynthesisstarwithafour-carboncompound.noncyclicphotophosphorylation非環(huán)形光合磷酸化作用Noncyclicphotophosphorylationiscoupledtononcyclicelectronflow,theelectronsbeingusedtoreduceNADP+aswellastomakeATP.photon光子Aparticlethathaszeromassorchargeandunitspin,thequantumoftheelectromagneticfieldandcarrieroftheelectromagneticforce.photophosphorylation光合磷酸化作用ThesynthesisofATPfromphosphateandADPduringphotosynthesis,usinglightenergy.photorespiration光呼吸Alight-dependenttypeofrespirationthatoccursinmostphotosyntheticplantsanddiffersfromnormal(ordark)respiration.photosynthesis光合作用Thesynthesisoforganiccompoundsbyreductionofcarbondioxideusinglightenergyabsorbedbychorophyll.photosystem光合系統(tǒng)Oneoftheclustersoflight-trappingpigmentsembeddedinphotosyntheticmembranes.PhotosystemIoperatesduringthecyclicpathway;photosystemⅡoperatesduringboththecyclicandnoncyclicpathways.ribulosebiphosphate(RUBP)核酮糖二磷酸AcompoundwithabackboneoffivecarbonatomsthatisrequiredforcarbonfixationintheCalvin-Bensoncycleofphotosynthesis.thylakoid類囊體Oneofanumberofflattenedfluid-filledsacsthatformthephotosyntheticlamellarsystemofchloroplasts,photosyntheticbacteria,andblue-greenalgae.CellularReproduction:MitosisandMeiosisTheNucleusandChromosomesThecellnucleusisthemainrepositoryofgeneticinformation.WithinthenucleusarethechromosomestightlycoiledstrandsofDNAandclustersofassociatedproteins.LongstretchesofthecontinuousDNAmoleculewindaroundtheseclustersofproteins,orhistones,formingbeadlikecomplexesknownasnucleosomes.Morecoilingandsupercoilingproducesadensechromosomestructure.EachlongstrandofDNAcombineswithhistonesandnonhistoneproteinstomakeupthesubstancechromatin.細(xì)胞核是貯藏遺傳信息的主要場(chǎng)所。DNA盤繞成螺旋線以及相關(guān)的成簇蛋白質(zhì)。DNA螺旋線纏繞成簇的組蛋白形成珠鏈狀的核小體。這些螺旋和超螺旋形成致密的染色體組結(jié)構(gòu)。每個(gè)長(zhǎng)鏈DNA與組蛋白和非組蛋白一起構(gòu)成染色質(zhì)物質(zhì)。Apictorialdisplayofanorganism'schromosomesinthecoiled,condensedstateisknownasakaryotype.Karyotyperevealthatinmostcellsallbutsexchromosomesarepresentastwocopies,referredtoashomologouspairs.Non-sexchromosomesarecalledautosomes.Organismswhosecellscontaintwosetsofparentalchromosomesarecalleddiploid;thosewithcellscontainingasinglesetofparentalchromosomesarecalledhaploid.染色體致密的超螺旋狀態(tài)我們稱染色體組。除了性染色體外，大多數(shù)細(xì)胞的染色體組成對(duì)出現(xiàn)，稱同源染色體對(duì)。非性染色體稱常染色體。生物細(xì)胞含有兩套父母本染色體的稱二倍體；含有單套染色體的稱單倍體。TheCellCycleThecellcycleisaregularsequenceinwhichthecellgrows,preparesfordivision,anddividestoformtwodaughtercells,eachofwhichthenrepeatsthecycle.Suchcyclingineffectmakessingle-celledorganismsimmortal.Manycellsinmulticellularorganisms,includinganimalmuscleandnervecells,eitherslowthecycleorbreakoutofitaltogether.在細(xì)胞生長(zhǎng)過(guò)程中，細(xì)胞循環(huán)遵循特定程序，分裂準(zhǔn)備，分裂成2個(gè)子細(xì)胞，子細(xì)胞再循環(huán)。此循環(huán)使得單細(xì)胞永生。多細(xì)胞生物中的許多細(xì)胞，包括動(dòng)物肌肉和神經(jīng)細(xì)胞，要么降低循環(huán)速度，要么同時(shí)分裂。Thenormalcellcycleconsistsoffourphases.ThefirstthreeincludeG1,theperiodofnormalmetabolism;Sphase,duringwhichnormalsynthesisofbiologicalmoleculescontinues,DNAisreplicated,andhistonesaresynthesized;andG2,abriefperiodofmetabolismandadditionalgrowth.TogethertheG1,S,andG2phasesarecalledinterphase.ThefourthphaseofthecellcycleisMphase,theperiodofmitosis,duringwhichthereplicatedchromosomescondenseandmoveandthecelldivides.Itisbelievedthatpropertiesofthecellcytoplasmcontrolthecellcycle,alongwithexternalstimulatorsandinhibitorssuchaschalones.正常細(xì)胞循環(huán)由4個(gè)時(shí)期組成。頭三期包括G1,正常新陳代謝；S期,正常新陳代謝同時(shí)，DNA復(fù)制，組蛋白合成；G2期，短期的新陳代謝和少許生長(zhǎng)。G1,S,和G2稱分裂間期。最后是M期，有絲分裂期，復(fù)制的染色體組濃縮，移動(dòng)并細(xì)胞分裂。據(jù)稱是染色質(zhì)控制了細(xì)胞循環(huán)，伴隨外部激活因子和抑制因子如抑素。Mitosis:PartitioningtheHereditaryMaterialBiologistsdividethemitoticcycleintofourphases.Atthebeginningofprophase前期thechromosomeseachconsistoftwohighlycondensedchromatidsattachedtoeachotheratacentromere.Asprophaseendsandmetaphase中期begins,thecondensed濃縮的chromosomesbecomeassociatedwiththespindle紡錘體.Eventuallythechromosomesbecomearrangedinaplane(calledthemetaphaseplate)atarightangletothespindlefibers.Next,duringanaphase后期,thetwosisterchromatidsofeachchromosomesplit,andonefromeachpairisdrawntowardeachpoleofthecell.Duringtelophase末期nuclearenvelopes包膜begintoformaroundeachsetofchromosomes,anddivisionofthecytoplasmtakesplace.生物學(xué)家將有絲分裂劃分為4個(gè)階段。分裂前期，高度濃縮的兩個(gè)染色單體通過(guò)著絲粒連接在一起。在分裂前期后期和分裂中期前期，濃縮的染色體與紡錘體相連，最后以正確的角度排列在赤道板上。在分裂后期，兩個(gè)姊妹單體分離，分別拽向細(xì)胞兩極。在分裂末期，在每套染色體周圍形成核膜，細(xì)胞質(zhì)發(fā)生分裂。Asmitosisproceeds,thespindlemicrotubulesplayacrucialroleinensuringthatbothpairedandseparatedchromatids染色單體moveintherightdirectionsatthepropertimes.Eachhalfofthespindleformsasmicrotubulesextendfromeachpoleofadividingcelltotheregionofthemetaphaseplate.Duringprophase,othermicrotubules,thecentromeric著絲粒fibers,extendoutwardfromthespindlepolestostructuresonthechromosomescalledkinetochores著絲粒.Duringanaphasethefibersbegintoshorten,andthechromatidsbegintomoveapart.在有絲分裂過(guò)程中，是紡錘體微管確保了染色單體在適當(dāng)時(shí)間以正確方向進(jìn)行分離。紡錘體微管由兩極向赤道板延伸。在分裂前期，其它微管，著絲粒纖維延伸到染色體的動(dòng)粒。在分裂后期，纖維開始變短，染色單體分離。Thespindleformsdifferentlyinplantandanimalcells.Ina