光合作用英文版-Photosynthesis

•Almostallplantsarephotosyntheticautotrophs,asaresomebacteriaandprotists–Autotrophsgeneratetheirownorganicmatterthroughphotosynthesis–Sunlightenergyistransformedtoenergystoredintheformofchemicalbonds(a)Mosses,ferns,andfloweringplants(b)Kelp(c)Euglena(d)CyanobacteriaTHEBASICSOFPHOTOSYNTHESISLightEnergyHarvestedbyPlants&OtherPhotosyntheticAutotrophs6CO2+6H2O+lightenergy→C6H12O6+6O2WHYAREPLANTSGREEN?PlantCellshaveGreenChloroplastsThethylakoidmembraneofthechloroplastisimpregnatedwithphotosyntheticpigments(i.e.,chlorophylls,carotenoids).•ChloroplastsabsorblightenergyandconvertittochemicalenergyLightReflectedlightAbsorbedlightTransmittedlightChloroplastTHECOLOROFLIGHTSEENISTHECOLORNOTABSORBED•PhotosynthesisistheprocessbywhichautotrophicorganismsuselightenergytomakesugarandoxygengasfromcarbondioxideandwaterANOVERVIEWOFPHOTOSYNTHESISCarbondioxideWaterGlucoseOxygengasPHOTOSYNTHESIS•TheCalvincyclemakessugarfromcarbondioxide–ATPgeneratedbythelightreactionsprovidestheenergyforsugarsynthesis–TheNADPHproducedbythelightreactionsprovidestheelectronsforthereductionofcarbondioxidetoglucoseLightChloroplastLightreactionsCalvincycleNADPADP+P•Thelightreactionsconvertsolarenergytochemicalenergy–ProduceATP&NADPHANOVERVIEWOFPHOTOSYNTHESISPHOTOSYNTHESIS•SunlightprovidesENERGYCO2+H2OproducesGlucose+Oxygen6CO2+6H2OC6H12O6+6O2StepsofPhotosynthesis•Lighthitsreactioncentersofchlorophyll,foundinchloroplasts•Chlorophyllvibratesandcauseswatertobreakapart.•Oxygenisreleasedintoair•HydrogenremainsinchloroplastattachedtoNADPH•“THELIGHTREACTION”StepsofPhotosynthesis•TheDARKReactions=CalvinCycle•CO2fromatmosphereisjoinedtoHfromwatermolecules(NADPH)toformglucose•Glucosecanbeconvertedintoothermoleculeswithyummyflavors!•Inmostplants,photosynthesisoccursprimarilyintheleaves,inthechloroplasts•Achloroplastcontains:–stroma,afluid–grana,stacksofthylakoids•Thethylakoidscontainchlorophyll–ChlorophyllisthegreenpigmentthatcaptureslightforphotosynthesisPhotosynthesisoccursinchloroplasts•ThelocationandstructureofchloroplastsLEAFCROSSSECTIONMESOPHYLLCELLLEAFChloroplastMesophyllCHLOROPLASTIntermembranespaceOutermembraneInnermembraneThylakoidcompartmentThylakoidStromaGranumStromaGrana•ChloroplastscontainseveralpigmentsChloroplastPigments–Chlorophylla–Chlorophyllb–Carotenoids–XanthophyllFigure7.7Chlorophylla&b•Chlahasamethylgroup•ChlbhasacarbonylgroupPorphyrinringdelocalizede-PhytoltailDifferentpigmentsabsorblightdifferentlyCyclicPhotophosphorylation•ProcessforATPgenerationassociatedwithsomePhotosyntheticBacteria•ReactionCenter=700nmWater-splittingphotosystemNADPH-producingphotosystemATPmill•TwotypesofphotosystemscooperateinthelightreactionsPrimaryelectronacceptorPrimaryelectronacceptorPhotonsPHOTOSYSTEMIPHOTOSYSTEMIIEnergyforsynthesisofbychemiosmosisNoncyclicPhotophosphorylation•PhotosystemIIregainselectronsbysplittingwater,leavingO2gasasaby-product•TheO2liberatedbyphotosynthesisismadefromtheoxygeninwater(H+ande-)PlantsproduceO2gasbysplittingH2O•Twoconnectedphotosystemscollectphotonsoflightandtransfertheenergytochlorophyllelectrons•Theexcitedelectronsarepassedfromtheprimaryelectronacceptortoelectrontransportchains–TheirenergyendsupinATPandNADPHInthelightreactions,electrontransportchainsgenerateATP,NADPH,&O2•TheelectrontransportchainsarearrangedwiththephotosystemsinthethylakoidmembranesandpumpH+throughthatmembrane–TheflowofH+backthroughthemembraneisharnessedbyATPsynthasetomakeATP–Inthestroma,theH+ionscombinewithNADP+toformNADPHChemiosmosispowersATPsynthesisinthelightreactions2H+1/2Water-splittingphotosystemReaction-centerchlorophyllLightPrimaryelectronacceptorEnergytomakePrimaryelectronacceptorPrimaryelectronacceptorNADPH-producingphotosystemLightNADP123HowtheLightReactionsGenerateATPandNADPH•TheproductionofATPbychemiosmosisinphotosynthesisThylakoidcompartment(highH+)ThylakoidmembraneStroma(lowH+)LightAntennamoleculesLightELECTRONTRANSPORTCHAINPHOTOSYSTEMIIPHOTOSYSTEMIATPSYNTHASESummary—LightDependentReactionsa.Overallinputlightenergy,H2O.b.OveralloutputATP,NADPH,O2.•AnimationisoftheCalvinCycleNotewhathappenstothecarbondioxideandwhattheendproductis.•SecondanimationoftheCalvinCycleisveryclearandevendoesthemolecularbookkeepingforyou.LightIndependentReactionsakaCalvinCycleCarbonfromCO2isconvertedtoglucose(ATPandNADPHdrivethereductionofCO2toC6H12O6.)LightIndependentReactionsakaCalvinCycleCO2isaddedtothe5-CsugarRuBPbytheenzymerubisco.Thisunstable6-CcompoundsplitstotwomoleculesofPGAor3-phosphoglycericacid.PGAisconvertedtoGlyceraldehyde3-phosphate(G3P),twoofwhichbondtoformglucose.G3Pisthe3-Csugarformedbythreeturnsofthecycle.Summary—LightIndependentReactionsa.OverallinputCO2,ATP,NADPH.b.Overalloutputglucose.Review:PhotosynthesisuseslightenergytomakefoodmoleculesLightChloroplastPhotosystemIIElectrontransportchainsPhotosystemICALVINCYCLEStromaLIGHTREACTIONSCALVINCYCLECellularrespirationCelluloseStarchOtherorganiccompounds•AsummaryofthechemicalprocessesofphotosynthesisTypesofPhotosynthesisC3C4CAMRubisco:theworld’sbusiestenzyme!CompetingReactions•RubiscograbsCO2,“fixing”i