Photosynthesis - Definition, Process, and Diagrams - BYJU'S

Photosynthesis is a process by which phototrophs convert light energy into chemical energy, which is later used to fuel cellular activities. BiologyBiologyArticlePhotosynthesis Photosynthesis Photosynthesisisaprocessbywhichphototrophsconvertlightenergyintochemicalenergy,whichislaterusedtofuelcellularactivities.Thechemicalenergyisstoredintheformofsugars,whicharecreatedfromwaterandcarbondioxide. WhatisPhotosynthesis Process Equation SitesOfPhotosynthesis Factors ChlorophyllStructure PhotosyntheticPigment Importance Photosynthesisdefinitionstatesthattheprocessexclusivelytakesplaceinthechloroplaststhroughphotosyntheticpigmentssuchaschlorophylla,chlorophyll b,caroteneandxanthophyll.Allgreenplantsandafewotherautotrophicorganismsutilize photosynthesistosynthesizenutrientsbyusingcarbondioxide,waterandsunlight.Theby-productofthephotosynthesisprocessisoxygen.Letushaveadetailedlookattheprocess,reactionandimportanceofphotosynthesis. WhatIsPhotosynthesisinBiology? Theword“photosynthesis”isderivedfromtheGreekwords phōs (pronounced:“fos”)and σύνθεσις(pronounced:“synthesis“)Phōsmeans“light”andσύνθεσις means,“combiningtogether.”Thismeans“combiningtogetherwiththehelpoflight.” Photosynthesisalsoappliestootherorganismsbesidesgreenplants.Theseincludeseveralprokaryotessuchascyanobacteria,purplebacteriaandgreensulfurbacteria.Theseorganismsexhibitphotosynthesisjustlikegreenplants.Theglucoseproducedduringphotosynthesisisthenusedtofuelvariouscellularactivities.Theby-productofthisphysio-chemicalprocessisoxygen. Avisualrepresentationofthephotosynthesisreaction Photosynthesisisalsousedbyalgaetoconvertsolarenergyintochemicalenergy.Oxygenisliberatedasaby-productandlightisconsideredasamajorfactortocompletetheprocessofphotosynthesis. Photosynthesisoccurswhenplantsuselightenergytoconvertcarbondioxideandwaterintoglucoseandoxygen.Leavescontainmicroscopiccellularorganellesknownaschloroplasts. Eachchloroplastcontainsagreen-colouredpigmentcalledchlorophyll.Lightenergyisabsorbedbychlorophyllmoleculeswhereascarbondioxideandoxygenenterthroughthetinyporesofstomatalocatedintheepidermisofleaves. Anotherby-productofphotosynthesisissugarssuchasglucoseandfructose. Thesesugarsarethensent totheroots,stems,leaves,fruits,flowersandseeds.Inotherwords,thesesugarsareusedbytheplantsasanenergysource,whichhelpsthemtogrow.Thesesugarmoleculesthencombinewitheachothertoformmorecomplexcarbohydrateslikecelluloseandstarch.Thecelluloseisconsideredasthestructuralmaterialthatisusedinplantcellwalls. AlsoRead: PhotosynthesisinHigherplants WhereDoesThisProcessOccur? Chloroplastsarethe sitesofphotosynthesis inplantsandblue-greenalgae.  Allgreenpartsofaplant,includingthe greenstems,greenleaves, andsepals– floralpartscompriseofchloroplasts–greencolourplastids.Thesecellorganellesarepresentonlyinplantcellsandare locatedwithinthemesophyllcellsofleaves. FactorsAffectingPhotosynthesis Photosynthesisprocessrequiresseveralfactorssuchas: LightIntensity:Increasedlightintensityresultsinahigherrateofphotosynthesis.Ontheotherhand,lowlightintensityresultsinalowerrateofphotosynthesis. TheconcentrationofCO2:Higherconcentrationofcarbondioxidehelpsinincreasingtherateofphotosynthesis.Usually,carbondioxideintherangeof300–400PPMisadequateforphotosynthesis. Temperature:Forefficientexecutionofphotosynthesis,itisimportanttohaveatemperaturerangebetween25°to35°C. Water:Aswaterisanimportantfactorinphotosynthesis,itsdeficiencycanleadtoproblemsintheintakeofcarbondioxide.Thescarcityofwaterleadstotherefusalofstomatalopeningtoretaintheamountofwatertheyhavestoredinside. Pollution:Industrialpollutantsandotherparticulatesmaysettleontheleafsurface.Thiscanblocktheporesofstomatawhichmakesitdifficulttotakeincarbondioxide. AlsoRead: PhotosynthesisEarlyExperiments PhotosynthesisEquation Photosynthesisreactioninvolvestworeactants,carbondioxideandwater.Thesetworeactantsyieldtwoproducts,namely,oxygenandglucose. Hence,thephotosynthesisreactionisconsideredtobeanendothermicreaction.Followingisthephotosynthesisformula: 6CO2   +  6H2O —> C6H12O6 +6O2 Unlikeplants,certainbacteriathatperform photosynthesisdonotproduceoxygenastheby-productofphotosynthesis.Suchbacteriaarecalled anoxygenicphotosynthetic bacteria.Thebacteriathatdoproduceoxygenasaby-productofphotosynthesisarecalled oxygenicphotosynthetic bacteria. PhotosyntheticPigments Therearefourdifferent typesofpigmentspresentinleaves: Chlorophylla Chlorophyllb Xanthophylls Carotenoids StructureOfChlorophyll Thestructureof Chlorophyllconsistsof4nitrogenatomsthatsurroundamagnesiumatom.Ahydrocarbontailisalsopresent.Picturedaboveischlorophyll-f, whichismoreeffectiveinnear-infraredlightthan chlorophyll-a Chlorophyllisagreenpigmentfoundinthechloroplastsofthe plantcell andinthemesosomesofcyanobacteria.Thisgreencolourpigmentplaysavitalroleintheprocessofphotosynthesisbypermittingplantstoabsorbenergyfromsunlight.Chlorophyllisamixtureofchlorophyll-a andchlorophyll-b.Besidesgreenplants,otherorganismsthatperformphotosynthesiscontainvariousotherformsofchlorophyllsuchas chlorophyll-c1,  chlorophyll-c2,  chlorophyll-dandchlorophyll-f. AlsoRead: BiologicalPigments ProcessOfPhotosynthesis Atthecellularlevel, thephotosynthesisprocesstakesplaceincellorganellescalledchloroplasts.Theseorganellescontainagreen-colouredpigmentcalledchlorophyll,whichisresponsibleforthecharacteristicgreencolourationoftheleaves. Asalreadystated,photosynthesisoccursintheleavesandthespecializedcellorganellesresponsibleforthisprocessiscalledthechloroplast.Structurally,aleafcomprisesapetiole,epidermisandalamina.Thelaminaisusedforabsorptionofsunlightandcarbondioxideduring photosynthesis. StructureofChloroplast.Notethepresenceofthethylakoid “PhotosynthesisSteps:” Duringtheprocessofphotosynthesis,carbondioxideentersthroughthestomata,waterisabsorbedbytheroothairsfromthesoilandiscarriedtotheleavesthroughthexylemvessels.Chlorophyllabsorbsthelightenergyfromthesuntosplitwatermoleculesintohydrogenandoxygen. Thehydrogenfromwatermoleculesandcarbondioxideabsorbedfromtheairareusedintheproductionofglucose.Furthermore,oxygenisliberatedoutintotheatmospherethroughtheleavesasawasteproduct. Glucoseisasourceoffoodforplantsthatprovideenergyfor growthanddevelopment,whiletherestisstoredintheroots,leavesandfruits,fortheirlateruse. Pigmentsareotherfundamentalcellularcomponentsofphotosynthesis.Theyarethemoleculesthatimpartcolourandtheyabsorblightatsomespecificwavelengthandreflectbacktheunabsorbedlight.Allgreenplantsmainlycontainchlorophylla,chlorophyllbandcarotenoidswhicharepresentinthethylakoidsofchloroplasts.Itisprimarilyusedtocapturelightenergy.Chlorophyll-aisthemainpigment. Theprocessofphotosynthesisoccursintwostages: Light-dependentreactionorlightreaction Lightindependentreactionordarkreaction StagesofPhotosynthesisinPlantsdepictingthetwophases– Lightreactionand Darkreaction LightReactionofPhotosynthesis (or)Light-dependentReaction Photosynthesisbeginswiththelightreactionwhichiscarriedoutonlyduringthedayinthepresenceofsunlight.Inplants,thelight-dependentreactiontakesplaceinthethylakoidmembranesofchloroplasts. TheGrana,membrane-boundsacslikestructurespresentinsidethethylakoidfunctionsbygatheringlightandiscalledphotosystems. Thesephotosystemshavelargecomplexesofpigmentandproteinsmoleculespresentwithintheplantcells,whichplaytheprimaryroleduringtheprocessoflightreactionsofphotosynthesis. Therearetwotypesofphotosystems:photosystemIandphotosystemII. Underthelight-dependentreactions,thelightenergyisconvertedtoATPandNADPH,whichareusedinthesecondphaseofphotosynthesis. Duringthelightreactions,ATPandNADPHaregeneratedbytwoelectron-transportchains,waterisusedandoxygenisproduced. Thechemicalequationinthelightreactionofphotosynthesiscanbereducedto: 2H2O+2NADP++3ADP+3Pi→O2+2NADPH+3ATP DarkReactionofPhotosynthesis (or) Light-independentReaction Darkreactionisalsocalledcarbon-fixingreaction. Itisalight-independentprocessinwhichsugarmoleculesareformedfromthewaterandcarbondioxidemolecules. ThedarkreactionoccursinthestromaofthechloroplastwheretheyutilizetheNADPHandATPproductsofthelightreaction. PlantscapturethecarbondioxidefromtheatmospherethroughstomataandproceedtotheCalvinphotosynthesiscycle. IntheCalvincycle,theATPandNADPHformedduringlightreactiondrivethereactionandconvert6moleculesofcarbondioxideintoonesugarmoleculeorglucose. Thechemicalequationforthedarkreactioncanbereducedto: 3CO2+6NADPH+5H2O+9ATP→G3P+2H++6NADP++9ADP+8Pi *G3P–glyceraldehyde-3-phosphate CalvinphotosynthesisCycle(DarkReaction) AlsoRead: CyclicAndNon-CyclicPhotophosphorylation ImportanceofPhotosynthesis Photosynthesisisessentialfortheexistenceofalllifeonearth.Itservesacrucialroleinthefoodchain–theplantscreatetheirfoodusingthisprocess,thereby,formingtheprimaryproducers. Photosynthesisisalsoresponsiblefortheproductionofoxygen–whichisneededbymostorganismsfortheirsurvival. FrequentlyAskedQuestions1.WhatisPhotosynthesis?Explaintheprocessofphotosynthesis.Photosynthesisisabiologicalprocessutilizedbyallgreenplantstosynthesizetheirownnutrients. Theprocessofphotosynthesisrequires solarenergy,waterandcarbondioxide.Theby-productofthisprocessisoxygen.2.WhatisthesignificanceofPhotosynthesis?Duringphotosynthesis,oxygengasisliberatedoutintotheenvironmentandisutilizedbyhumans,animalsandotherlivingspeciesduringtheprocessofrespiration.3.Listoutthefactorsinfluencing Photosynthesis.Thereareseveralfactorsthataffecttherateofphotosynthesis.Lightintensity,water,soilpH,carbondioxideconcentration,temperatureandotherclimaticconditionsarethemainfactorsaffecting therateofphotosynthesis.4.WhatarethedifferentstagesofPhotosynthesis?Photosynthesistakesplaceintwo stages,namelylight-dependentreactionsandlight-independentreactions.Light-dependentreactionsarealsocalledlightreactionsandoccurduringthedaytime.Light-independentreactionisalsocalledthedarkreactionortheCalvincycle.5.WhatistheCalvinCycle?TheCalvincycleisalsocalledthelight-independentreaction.ThecompleteprocessoftheCalvincycle takesplaceinthestroma ofthechloroplasts.6.WritedownthePhotosynthesisEquation.6CO2    +  6H2O —> C6H12O6  +6O2RegisteratBYJU’SBiologytoexploremorephotosynthesisnotesornotesforotherrelatedconcepts.ImportantMCQsonPhotosynthesis QuizOfTheDay! Q5 PutyourunderstandingofthisconcepttotestbyansweringafewMCQs.Click‘StartQuiz’tobegin! Selectthecorrectanswerandclickonthe“Finish”buttonCheckyourscoreandanswersattheendofthequiz StartQuiz Congrats! VisitBYJU’SforallBiologyrelatedqueriesandstudymaterials Yourresultisasbelow 0outof0arewrong 0outof0arecorrect 0outof0areUnattempted ViewQuizAnswersandAnalysis BIOLOGYRelatedLinks WhatIsAdulteration WhyIsBiodiversityImportant PlacentaDefinition MitosisMeaning ExocrineGlands PartsOfNephron SeedDispersalByWater ElisaPrinciple DNAModel GerminationOfPollenOnStigma 19Comments Marotiingole September26,2019at2:12pm Nice Reply rakchita April24,2020at11:37am veryuseful Reply Umang May10,2020at8:24am It’sveryhelpful☺️ Reply Marvellous May15,2020at4:46am PleaseWhatIsMeantBy300-400PPM Reply nazia July7,2020at6:02pm PPMstandsforParts-Per-Million.Itcorrespondstosayingthat300PPMofcarbondioxideindicatesthatifonemilliongasmoleculesarecounted,300outofthemwouldbecarbondioxide.Theremainingninehundredninety-ninethousandsevenhundredareothergasmolecules. Reply AmritaDas June2,2020at7:59pm ThankyouverymuchByju’s!Icouldn’tfindtheansweranywhere.ButluckilyIhituponthiswebsite.Awesomeexplanationandillustration. Reply Zac August5,2020at3:24pm byjus=Wow! Reply ds August5,2020at3:26pm Verysuper Reply Jyothsna August21,2020at8:31pm Ithelpsmealotthankyou Reply Favour August23,2020at12:16pm Thanksinamillion IloveByjus! Reply Maheshwari August28,2020at9:51am SuperByjus Reply Rashi September6,2020at1:32pm Thankshelpedalot Reply Hilal September16,2020at9:02am Veryinterestingandhelpfulsite. Reply Urvigpoojary September26,2020at10:28am Niceitisveryuesful Reply Nabinojha October24,2020at9:36am It’sveryuseful👍ThankyouByju’s Reply SushilSapkal November2,2020at6:59pm ThankyouverymuchByju’s!Icouldn’tfindtheansweranywhere.ButluckilyIhituponthiswebsite.Awesomeexplanationandillustration. Thankyou Reply samesha December9,2020at11:17am ThankyouBYJU’Sforhelpingmeinfurtherclarifyingmyconcepts Reply SteveNjekwa January3,2021at6:25pm Excellentmaterialeasytounderstand Reply AlasanaBeyai January16,2021at6:59pm Indeed,it’spreciseandunderstandable.Ilikeit. 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