An Overview of Calvin Cycle - Stages Of C3 Cycle - Byju's

Calvin cycle is also known as the C3 cycle. It is the cycle of chemical reactions where the carbon from the carbon cycle is fixed into sugars. BiologyBiologyArticleCalvinCycle CalvinCycle Photosynthesisisthebiochemicalprocessthatoccursinallgreenplantsorautotrophsproducingorganicmoleculesfromcarbondioxide(CO2).Theseorganicmoleculescontainmanycarbon-hydrogen(C–H)bondsandarehighlyreducedcomparedtoCO2. TherearetwostagesofPhotosynthesis– Light-dependentreactions–Asthenamesuggests,itrequireslightandmainlyoccursduringthedaytime. Light-independentreactions–ItisalsocalledthedarkreactionorCalvincycleorC3cycle.Thisreactionoccursbothinthepresenceandabsenceofsunlight. TableofContents Definition Explanation Diagram Stages CarbonFixation Reduction Regeneration Products KeyPoints LetushaveadetailedlookatCalvinCycleorC3cyclealongwithitsstages. CalvinCycleDefinition “CalvincycleorC3cycleisdefinedasasetofchemicalreactionsperformedbytheplantstoreducecarbondioxideandothercompoundsintoglucose.” WhatisCalvinCycle? CalvincycleisalsoknownastheC3cycleorlight-independentordarkreactionofphotosynthesis.However,itismostactiveduringthedaywhenNADPHandATPareabundant.Tobuildorganicmolecules,theplantcellsuserawmaterialsprovidedbythelightreactions: 1.Energy:ATPprovidedbycyclicandnoncyclicphotophosphorylation,whichdrivestheendergonicreactions. 2.Reducingpower:NADPHprovidedbyphotosystemIisthesourceofhydrogenandtheenergeticelectronsrequiredtobindthemtocarbonatoms.Muchofthelightenergycapturedduringphotosynthesisendsupintheenergy-richC—Hbondsofsugars. Plantsstorelightenergyintheformofcarbohydrates,primarilystarchandsucrose.ThecarbonandoxygenrequiredforthisprocessareobtainedfromCO2,andtheenergyforcarbonfixationisderivedfromtheATPandNADPHproducedduringthephotosynthesisprocess. TheconversionofCO2tocarbohydrateiscalledCalvinCycleorC3cycleandisnamedafterMelvinCalvinwhodiscoveredit.TheplantsthatundergotheCalvincycleforcarbonfixationareknownasC3plants. CalvinCyclerequirestheenzymeribulose-1,5-bisphosphatecarboxylase/oxygenasecommonlycalledRuBisCO.Itgeneratesthetriosephosphates,3-phosphoglycerate(3-PGA),glyceraldehyde-3P(GAP),anddihydroxyacetonephosphate(DHAP),allofwhichareusedtosynthesizethehexosephosphatesfructose-1,6-bisphosphateandfructose6-phosphate. Alsoread:Photosynthesis C3CycleDiagram TheCalvincyclediagrambelowshowsthedifferentstagesofCalvinCycleorC3cyclethatincludecarbonfixation,reduction,andregeneration. StagesofC3Cycle CalvincycleorC3cyclecanbedividedintothreemainstages: Carbonfixation ThekeystepintheCalvincycleistheeventthatreducesCO2. CO2bindstoRuBPinthekeyprocesscalledcarbonfixation,formingtwo-threecarbonmoleculesofphosphoglycerate.Theenzymethatcarriesoutthisreactionisribulosebisphosphatecarboxylase/oxygenase,whichisverylargewithafour-subunitandpresentinthechloroplaststroma.Thisenzymeworksverysluggishly,processingonlyaboutthreemoleculesofRuBPpersecond(atypicalenzymeprocessofabout1000substratemoleculespersecond).Inatypicalleaf,over50%ofalltheproteinisRuBisCO.Itisthoughttobethemostabundantproteinontheearth. Reduction ItisthesecondstageofCalvincycle.The3-PGAmoleculescreatedthroughcarbonfixationareconvertedintomoleculesofsimplesugar–glucose. ThisstageobtainsenergyfromATPandNADPHformedduringthelight-dependentreactionsofphotosynthesis.Inthisway,Calvincyclebecomesapathwayinwhichplantsconvertsunlightenergyintolong-termstoragemolecules,suchassugars.TheenergyfromtheATPandNADPHistransferredtothesugars. Thisstepisknownasreductionsinceelectronsaretransferredto3-PGAmoleculestoformglyceraldehyde-3phosphate. Regeneration ItisthethirdstageoftheCalvincycleandisacomplexprocessthatrequiresATP.Inthisstage,someoftheG3Pmoleculesareusedtoproduceglucose,whileothersarerecycledtoregeneratetheRuBPacceptor. Alsoread:LightreactionAndDarkreaction ProductsofC3Cycle OnemoleculeofcarbonisfixedateachturnoftheCalvincycle. Onemoleculeofglyceraldehyde-3phosphateiscreatedinthreeturnsoftheCalvincycle. Twomoleculesofglyceraldehyde-3phosphatecombinetogethertoformoneglucosemolecule. 3ATPand2NADPHmoleculesareusedduringthereductionof3-phosphoglycericacidtoglyceraldehyde-3phosphateandintheregenerationofRuBP. 18ATPand12NADPHareconsumedintheproductionof1glucosemolecule. KeyPointsonC3Cycle C3cyclereferstothedarkreactionofphotosynthesis. Itisindirectlydependentonlightandtheessentialenergycarriersareproductsoflight-dependentreactions. InthefirststageoftheCalvincycle,thelight-independentreactionsareinitiatedandcarbondioxideisfixed. InthesecondstageoftheC3cycle,ATPandNADPHreduce3PGAtoG3P.ATPandNADPHarethenconvertedintoATPandNADP+. Inthelaststage,RuBPisregenerated.Thishelpsinmorecarbondioxidefixation. AlsoRead:C3andC4Pathways DiscovermoreaboutCalvincycleorC3cycle,itsstages,andothertopicsonly@BYJU’SBiology FrequentlyAskedQuestionsWhatisCalvinCycle? CalvincycleisalsoknownastheC3cycle.Itisthecycleofchemicalreactionswherethecarbonfromthecarboncycleisfixedintosugars.Itoccursinthechloroplastoftheplantcell. WhatarethedifferentstepsinvolvedintheCalvincycle? ThedifferentstepsinvolvedintheCalvincycleinclude: Carbonfixation Reduction Regeneration WhataretheendproductsofC3cycle? ADP,NADP,andglucosearetheendproductsoftheC3cycle.ADPandNADPareproducedinthefirststageofC3cycle.Inthesecondstage,glucoseisproduced. WhatiscarbonfixationintheCalvincycle? InthecarbonfixationoftheCalvincycle,thecarbondioxideisfixedtostableorganicintermediates. WhyisthethirdstepoftheCalvincyclecalledtheregenerationstep? ThethirdstepisknownasregenerationbecauseRibulose-bisphosphatethatbeginsthecycleisregeneratedfromG3P. LearnBetterthroughBYJU'SQuiz Q5 PutyourunderstandingofthisconcepttotestbyansweringafewMCQs.Click‘StartQuiz’tobegin! Selectthecorrectanswerandclickonthe“Finish”buttonCheckyourscoreandanswersattheendofthequiz StartQuiz Congrats! ExploreBYJU’SformoreconceptsonBiology Yourresultisasbelow 0outof0arewrong 0outof0arecorrect 0outof0areUnattempted ViewQuizAnswersandAnalysis BIOLOGYRelatedLinks WhatIsPhagocytosis MitochondriaMeaning WhatIsSpinning HumanLifeCycle PlantRoots MicturitionMeaning NervousTissueDiagram PartsOfTheNose RespirationMeaning WhatAreNeurotransmitters 2Comments AdityaPrakashNayak May22,2020at9:30am Extremelyhelpful Veryniceanswers Iamalsojoinedpremiummemberofbyjusfor4years Theteachersandtechnologyarenice. Reply SumanDwivedi March5,2021at8:58am Niceapp Reply LeaveaCommentCancelreplyYourMobilenumberandEmailidwillnotbepublished.Requiredfieldsaremarked* * SendOTP DidnotreceiveOTP? 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