光合作用英文版Photosynth.ppt

Almostallplantsarephotosyntheticautotrophs asaresomebacteriaandprotists AutotrophsgeneratetheirownorganicmatterthroughphotosynthesisSunlightenergyistransformedtoenergystoredintheformofchemicalbonds a Mosses ferns andfloweringplants b Kelp c Euglena d Cyanobacteria THEBASICSOFPHOTOSYNTHESIS LightEnergyHarvestedbyPlants OtherPhotosyntheticAutotrophs 6CO2 6H2O lightenergy C6H12O6 6O2 WHYAREPLANTSGREEN PlantCellshaveGreenChloroplasts Thethylakoidmembraneofthechloroplastisimpregnatedwithphotosyntheticpigments i e chlorophylls carotenoids Chloroplastsabsorblightenergyandconvertittochemicalenergy Light Reflectedlight Absorbedlight Transmittedlight Chloroplast THECOLOROFLIGHTSEENISTHECOLORNOTABSORBED Photosynthesisistheprocessbywhichautotrophicorganismsuselightenergytomakesugarandoxygengasfromcarbondioxideandwater ANOVERVIEWOFPHOTOSYNTHESIS Carbondioxide Water Glucose Oxygengas PHOTOSYNTHESIS TheCalvincyclemakessugarfromcarbondioxideATPgeneratedbythelightreactionsprovidestheenergyforsugarsynthesisTheNADPHproducedbythelightreactionsprovidestheelectronsforthereductionofcarbondioxidetoglucose Light Chloroplast Lightreactions Calvincycle NADP ADP P ThelightreactionsconvertsolarenergytochemicalenergyProduceATP NADPH ANOVERVIEWOFPHOTOSYNTHESIS PHOTOSYNTHESIS SunlightprovidesENERGY CO2 H2OproducesGlucose Oxygen 6CO2 6H2OC6H12O6 6O2 StepsofPhotosynthesis Lighthitsreactioncentersofchlorophyll foundinchloroplasts Chlorophyllvibratesandcauseswatertobreakapart Oxygenisreleasedintoair HydrogenremainsinchloroplastattachedtoNADPH THELIGHTREACTION StepsofPhotosynthesis TheDARKReactions CalvinCycle CO2fromatmosphereisjoinedtoHfromwatermolecules NADPH toformglucose Glucosecanbeconvertedintoothermoleculeswithyummyflavors Inmostplants photosynthesisoccursprimarilyintheleaves inthechloroplastsAchloroplastcontains stroma afluidgrana stacksofthylakoidsThethylakoidscontainchlorophyllChlorophyllisthegreenpigmentthatcaptureslightforphotosynthesis Photosynthesisoccursinchloroplasts Thelocationandstructureofchloroplasts LEAFCROSSSECTION MESOPHYLLCELL LEAF Chloroplast Mesophyll CHLOROPLAST Intermembranespace Outermembrane Innermembrane Thylakoidcompartment Thylakoid Stroma Granum Stroma Grana Chloroplastscontainseveralpigments ChloroplastPigments ChlorophyllaChlorophyllbCarotenoidsXanthophyll Figure7 7 Chlorophylla b ChlahasamethylgroupChlbhasacarbonylgroup Differentpigmentsabsorblightdifferently CyclicPhotophosphorylationProcessforATPgenerationassociatedwithsomePhotosyntheticBacteriaReactionCenter 700nm Photon Photon Water splittingphotosystem NADPH producingphotosystem ATPmill Twotypesofphotosystemscooperateinthelightreactions NoncyclicPhotophosphorylationPhotosystemIIregainselectronsbysplittingwater leavingO2gasasaby product TheO2liberatedbyphotosynthesisismadefromtheoxygeninwater H ande PlantsproduceO2gasbysplittingH2O TwoconnectedphotosystemscollectphotonsoflightandtransfertheenergytochlorophyllelectronsTheexcitedelectronsarepassedfromtheprimaryelectronacceptortoelectrontransportchainsTheirenergyendsupinATPandNADPH Inthelightreactions electrontransportchainsgenerateATP NADPH O2 TheelectrontransportchainsarearrangedwiththephotosystemsinthethylakoidmembranesandpumpH throughthatmembraneTheflowofH backthroughthemembraneisharnessedbyATPsynthasetomakeATPInthestroma theH ionscombinewithNADP toformNADPH ChemiosmosispowersATPsynthesisinthelightreactions 2H 1 2 Water splittingphotosystem Reaction centerchlorophyll Light Primaryelectronacceptor Energytomake Electrontransportchain Primaryelectronacceptor Primaryelectronacceptor NADPH producingphotosystem Light NADP 1 2 3 HowtheLightReactionsGenerateATPandNADPH TheproductionofATPbychemiosmosisinphotosynthesis Thylakoidcompartment highH Thylakoidmembrane Stroma lowH Light Antennamolecules Light ELECTRONTRANSPORTCHAIN PHOTOSYSTEMII PHOTOSYSTEMI ATPSYNTHASE Summary LightDependentReactions a Overallinputlightenergy H2O b OveralloutputATP NADPH O2 AnimationisoftheCalvinCycleNotewhathappenstothecarbondioxideandwhattheendproductis SecondanimationoftheCalvinCycleisveryclearandevendoesthemolecularbookkeepingforyou LightIndependentReactionsakaCalvinCycle CarbonfromCO2isconvertedtoglucose ATPandNADPHdrivethereductionofCO2toC6H12O6 LightIndependentReactionsakaCalvinCycle CO2isaddedtothe5 CsugarRuBPbytheenzymerubisco Thisunstable6 CcompoundsplitstotwomoleculesofPGAor3 phosphoglycericacid PGAisconvertedtoGlyceraldehyde3 phosphate G3P twoofwhichbondtoformglucose G3Pisthe3 Csugarformedbythreeturnsofthecycle Summary LightIndependentReactions a OverallinputCO2 ATP NADPH b Overalloutputglucose Review Photosynthesisuseslightenergytomakefoodmolecules Light Chloroplast PhotosystemIIElectrontransportchainsPhotosystemI CALVINCYCLE Stroma Electrons LIGHTREACTIONS CALVINCYCLE Cellularrespiration Cellulose Starch Otherorganiccompounds Asummaryofthechemicalprocessesofphotosynthesis TypesofPhotosynthesis C3C4CAM Rubisco theworld sbusiestenzyme CompetingReactions RubiscograbsCO2 fixing itintoacarbohydrateinthelightindependentreactions O2canalsoreactwithrubisco inhibitingitsactivesitenotgoodforglucoseoutputwastestimeandenergy occupiesRubisco Photorespiration WhenRubiscoreactswithO2insteadofCO2Occursunderthefollowingconditions IntenseLight highO2concentrations HighheatPhotorespirationisestimatedtoreducephotosyntheticefficiencyby25 Whyhighheat Whenitishot plantsclosetheirstomatatoconservewaterTheycontinuetodophotosynthesis useupCO2andproduceO2 createshighO2concentrationsinsidetheplant photorespirationoccurs C4Photosynthesis CertainplantshavedevelopedwaystolimittheamountofphotorespirationC4Pathway CAMPathway BothconvertCO2intoa4carbonintermediate C4Photosynthesis LeafAnatomy InC3plants thosethatdoC3photosynthesis allprocessesoccurinthemesophyllcells Imagetakenwithoutpermissionfrom C4Pathway InC4plantsphotosynthesisoccursinboththemesophyllandthebundlesheathcells Imagetakenwithoutpermissionfrom C4Pathway CO2isfixedintoa4 carbonintermediateHasanextraenzyme PEPCarboxylasethatinitiallytrapsCO2insteadofRubisco makesa4carbonintermediate C4Pathway The4carbonintermediateis smuggled intothebundlesheathcellThebundlesheathcellisnotverypermeabletoCO2CO2isreleasedfromthe4Cmalate goesthroughtheCalvinCycle HowdoestheC4Pathwaylimitphotorespiration Bundlesheathcellsarefarfromthesurface lessO2accessPEPCarboxylasedoesn thaveanaffinityforO2 allowsplanttocollectalotofCO2andconcentrateitinthebundlesheathcells whereRubiscois CAMPathway FixCO2atnightandstoreasa4carbonmoleculeKeepstomatesclosedduringdaytopreventwaterlossSamegeneralprocessasC4Pathway HowdoestheCAMPathwaylimitphotorespiration CollectsCO2atnightsothatitcanbemoreconcentratedduringthedayPlantcanstilldothecalvincycleduringthedaywithoutlosingwater SummaryofC4Photosynthesis C4PathwaySeparatesbyspace differentlocations CAMPathwaySeparatesreactionsbytime nightversusday