细胞生物学课件：Chapter5II energy generation in mitochondria and chloroplasts

ChloroplastandphotosynthesisComparisonofamitochondrionandachloroplast.

Thechloroplast.

Thisphotosyntheticorganellecontainsthreedistinctmembranes(theoutermembrane,theinnermembrane,andthethylakoidmembrane)thatdefinethreeseparateinternalcompartments(theintermembranespace,thestroma,andthethylakoidspace).Thethylakoidmembranecontainsalloftheenergy-generatingsystemsofthechloroplast.Inelectronmicrographsthismembraneappearstobebrokenupintoseparateunitsthatencloseindividualflattenedvesiclesbuttheseareprobablyjoinedintoasingle,highlyfoldedmembraneineachchloroplast.Asindicated,theindividualthylakoidsareinterconnected,andtheytendtostacktoformaggregatescalled

grana.

1、Chloroplastmembrane

(A)Awheatleafcellinwhichathinrimofcytoplasmcontainingchloroplastssurroundsalargevacuole.(B)Athinsectionofasinglechloroplast,showingthestarchgranulesandlipiddropletsthathaveaccumulatedinthestromaasaresultofthebiosynthesesoccurringthere.(C)Ahigh-magnificationviewofagranum,showingitsstackedthylakoidmembrane.(CourtesyofK.Plaskitt.)2、StromaStromacontainsmanymetabolicenzymeanditsowngenomeandgeneticsystem.Stromaalsocontainsaspecialsetofribosomes,RNAandDNA.核酮糖-1，5-二磷酸羧化酶/加氧酶（rebulose-1,5-biphosphatecarboxylase/oxygenase,Rubisco)3、ThylakoidGranaGranumthylakoidStromalamellaStromathylakoidThethylakoidmembranecontainallthelight-capturingsystems,theelectron-transportchain,andATPsynthase.Fiveproteincomplex:PSIIPSICytochromeb6/fcomplexCF0-CF1ATPsynthaseChla/blight-harvestingcomplexThemainfunctionofchloroplastphotosynthesisLightreactionCarbon-fixationreactionPrimaryreactionPhotosyntheticelectrontransferchainPhotophosphorylationC4C3CAMPigment-CHOinchlbProphyrinringTheratioofchlaandchlbis3:1Theratioofchlorophyllandcarotenoidis3:1Pigmentcontainchlorophyll,carotenoidandphycobilin.Chlorophyllcontainchlaandchlb.Carotenoidisaccessorypigment.Themaintypecontainβ-caroteneandlutein.

Primaryreaction约300个叶绿素分子和一些肽链构成。全部叶绿素b和大部分叶绿素a都是天线色素。集光复合体TheantennacomplexandphotochemicalreactioncenterinaphotosystemPheoinPIIChla（A0）

inPIPhotosyntheticelectrontransferchainphotosystemIphotosystemIIcytochromeb6/fcomplexPhotosystemIIP68014chlorophyllmolecule

吸收高峰为波长680nm处，又称P680。至少包括12条多肽链。位于EFs,EFu上，基粒与基质非接触区域的类囊体膜上。包括一个集光复合体（light-hawestingcomnplexⅡ，LHCⅡ）、一个反应中心和一个含锰原子的放氧复合体（oxygenevolvingcomplex）。D1多肽链上的酪氨酸残基COO-CH3N+HCH2OHMM3+M2+M+

M4+cytochromeb6/fcomplex可能以二聚体形成存在，每个单体含有四个不同的亚基。细胞色素b6（b563）、细胞色素f、铁硫蛋白、以及亚基Ⅳ（被认为是质体醌的结合蛋白）。（PSI）P700能被波长700nm的光激发，又称P700

。包含多条肽链，位于基粒与基质接触区和基质类囊体膜中。由集光复合体Ⅰ和作用中心构成。结合100个左右叶绿素分子、除了几个特殊的叶绿素为中心色素外，其它叶绿素都是天线色素。三种电子载体分别为A0（一个chla分子)、A1(为维生素K1)及3个不同的4Fe-4S。

Light-dependentreaction:Electrontransportinthethylakoidmembraneandnoncyclicphotophosphorylation:NoncyclicphotophosphorylationCyclicphotophosphorylation:CyclicphotophosphorylationPSIandPSII

Photosynthesisinachloroplast.

Waterisoxidizedandoxygenisreleasedinthephotosyntheticelectron-transferreactions,whilecarbondioxideisassimilated(fixed)toproducecarbohydrateinthecarbon-fixationreactions.Changesinredoxpotentialduringphotosynthesis.光合过程中氧化还原电势的变化Photosynthesis?resemblance?differenceComparisonofamitochondrionandachloroplast.

叶绿体功能示意图叶绿体的ATP合成酶结构示意图叶绿体类囊体膜中进行光合磷酸化的图解叶绿体类囊体膜上进行光合磷酸化（三）暗反应

C3途径(C3pathway)：亦称卡尔文

(Calvin)循环。CO2受体为RuBP，最初产物为3-磷酸甘油酸(PGA)。

C4途径(C4pathway)：亦称哈奇-斯莱克(Hatch-Slack)途径，CO2受体为PEP，最初产物为草酰乙酸(OAA)。景天科酸代谢途径（Crassulaceanacidmetabolismpathway，CAM途径）：夜间固定CO2产生有机酸，白天有机酸脱羧释放CO2，进行CO2固定。碳固定的循环类囊体膜上光合过程中的电子流动CarbondioxidefixationandthesynthesisofcarbohydrateinC3plants(Calvincycle)Figure

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Theinitialreactionincarbonfixation.

Thisreaction,inwhichcarbondioxideisconvertedintoorganiccarbon,iscatalyzedinthechloroplaststromabytheabundantenzymeribulosebisphosphatecarboxylase.Theproduct,3-phosphoglycerate,isalsoanimportantintermediateinglycolysis:thetwocarbonatomsshadedinblueareusedtoproducephosphoglycolatewhentheenzymeaddsoxygeninsteadofCO2。

ThestructureandfunctioninC4plants4.OrganelleDNAandproteinimportingA.OrganelleDNAThesizerangeoforganelleDNAissimilartothatofviralDNAs.MitDNA:from<6,000bp(plasmodiumfalciparum)～

>300,000bp(somelandplants).DNAofMitgenome(inmammals)≈16,500bp(<0.001%ofnucleargenome);Chlgenomesareabout10timeslargerandcontainabout120genes.ChlDNA:from70,000to200,000bp(genomeoflandplants);GenesinmtDNAencoderRNAs,tRNAs,andsomemitochondrialproteinsHumanmtDNA:16,569bp2rRNAs,22tRNAs,13polypeptides:NADHreductase.7sub.Ctyb-c1complex.1cytbCytoxidase.3subunitsATPsynthase:2F0sub

ProductsofmtgenesarenotexportedTheorganizationoftheliverwort(地钱)ChlgenomeB.MitandChlhavetheirowngeneticsystemsMitandChlareorganellessemiautocephaly.ThesynthesisofmtproteinsiscoordinatedC.ThetransportproteinintoMit.AndChl.TreeproteinstranslocatorsinMitmembranes:TOM,TIM,andOXAcomplexaremultimericmembraneprotein,thatcatalyzeproteintransportacrossMitmembrane,TOM,TIMstandfortranslocaseoftheouterandinnerMitmembranesrespectively.TOMfunctionsacrosstheoutermembrane;TIM(TIM23andTIM22)functionacrosstheinnermembrane.OXAmediatestheinsertionofinnermembraneproteinsthataresynthesizedwithintheMit.OXAalsohelpsTOMandTIMtoinsertsomeproteinsintothematrix.Translocationofprecursorstothematrixoccursatthesiteswheretheouterandinnermembranesareclosetogether;TheproteinimportbyMit:N-terminalsignalsequenceisrecognizedbyreceptorsofTOM;TheproteinistranslocatedacrossbothMitmembranesatornearspecialcontactsites.OnlyunfoldedproteinscanbeimportedintoMit;Mitprecursorproteinsremainunfoldedthroughinteractionswithhsp70chaperoneproteinsinthecytosolaftertheyaresynthesized.ATPhydrolysisandH+gradientareusedtodtiveproteinimportintoMitProteintransportintotheinnerMitmembraneandtheintermembranespacerequirestwosignalsequencesTwosignalsequencesarerequiredtodirectproteinstotheThylakoidmembraneinChl.TranslocationintothylakoidspaceorthylakoidMcanoccurbyanyoneofatleastfourroutes.5.TheproliferationandoriginofMitandChl.

A.

OrganellegrowthanddivisiondeterminethenumberofMitoc