Isihloko esithi “Ukusabela Okumnyama: Izinqubo Ezibalulekile Ku-Photosynthesis”
I-Pendahuluan
I-Photosynthesis inqubo ebalulekile eyenziwa izitshalo, ulwelwe, kanye nezinhlobo ezithile zamabhaktheriya ukuguqula amandla okukhanya abe amandla amakhemikhali. Le nqubo inezigaba ezimbili eziyinhloko: ukusabela kokukhanya kanye nokusabela okumnyama. Ukusabela kokukhanya, okuncike ekukhanyeni, kwenzeka kuma-thylakoid ama-chloroplast futhi kukhiqiza i-ATP ne-NADPH. Ngokuphambene nalokho, ukusabela okumnyama, okungadingi ukukhanya ngqo, kwenzeka ku-stroma yama-chloroplast futhi kusebenzisa i-ATP ne-NADPH ekhiqizwa ukusabela kokukhanya ukuze kwakhiwe i-glucose. Nakuba kubonakala kuyimfihlakalo, ukusabela okumnyama kudlala indima ebalulekile emjikelezweni wokuphila wezinto eziphilayo. Lesi sihloko sizoxoxa ngokujulile ngokusabela okumnyama ku-photosynthesis.
Ukusabela Okumnyama Nomjikelezo KaCalvin
Ukusabela okumnyama kuvame ukubizwa ngokuthi iCalvin Cycle, eqanjwe ngososayensi waseMelika uMelvin Calvin, owathi, kanye nozakwabo u-Andrew Benson noJames Bassham, bachaza ngempumelelo le ndlela ye-metabolic. ICalvin Cycle yenzeka ku-chloroplast stroma futhi iwuchungechunge lwemiphumela yamakhemikhali eguqula i-carbon dioxide kanye namakhemikhali e-organic abe yi-glucose. Le nqubo ingahlukaniswa ngezigaba ezintathu eziyinhloko: ukulungiswa kwe-carbon, ukunciphisa, kanye nokuvuselelwa.
1. Ukulungiswa Kwekhabhoni
Isinyathelo sokuqala ekuphenduleni okumnyama ukufakwa kwekhabhoni. Kulesi sinyathelo, i-carbon dioxide esemoyeni iqinisiwe, noma iboshwe, kuma-organic compounds. I-molecule yokuqala yokwamukela kulo mjikelezo yi-ribulose bisphosphate (RuBP), i-compound yama-carbon amahlanu. I-enzyme i-ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO2) yenza kube lula ukusabela phakathi kwe-RuBP ne-CO2, ikhiqize i-compound yama-carbon ayisithupha ehlukaniswa ngokushesha ibe ama-molecule amabili e-3-phosphoglycerate (3-PGA).
2. Ukunciphisa
Isigaba esilandelayo ukunciphisa, lapho ama-molecule e-3-PGA ebhekana nokusabela kokunciphisa ukuze akhe i-glyceraldehyde-3-phosphate (G3P). Le nqubo idinga i-ATP ne-NADPH ezikhiqizwa ngokusabela kokukhanya. Ngochungechunge lwezimpendulo ze-enzyme, i-3-PGA yamukela iqembu le-phosphate elivela ku-ATP kanye nama-electron asuka ku-NADPH, akhiqiza i-G3P. Amanye ama-molecule e-G3P abe esesetshenziselwa ukwenziwa kwe-glucose, kuyilapho okusele kusetshenziswa esigabeni sokuvuselelwa.
3. Ukuvuselelwa kabusha
Isigaba sokugcina somjikelezo kaCalvin ukuvuselelwa. Kulesi sigaba, ama-molecule e-G3P angasetshenziselwa ukwakheka kwe-glucose adlula ochungechungeni lwezimpendulo ze-enzyme ukuze avuselele i-RuBP, okuvumela umjikelezo ukuthi uphinde. Le nqubo idinga i-ATP eyengeziwe, futhi ukuqongelela kwe-ATP ne-NADPH kuyisihluthulelo sokuqhubeka komjikelezo.
Ukubaluleka Kokusabela Okumnyama
Omunye wemisebenzi eyinhloko yokusabela okumnyama ukuguqulwa kwe-CO2 ibe yizinhlanganisela eziphilayo, ekugcineni kukhiqize i-glucose. Le nqubo iyisisekelo sochungechunge lokudla lwe-ecosystem ngoba inikeza umthombo oyinhloko wokudla wezinto eziphilayo ezizenzakalelayo. Ngaphezu kwalokho, ukusabela okumnyama nakho kuyasiza ekulawuleni amazinga e-CO2 asemkhathini, anemiphumela ekulinganisweni kwesimo sezulu somhlaba wonke. Esikhathini eside, lokhu kusabela kudlala indima ekwakhekeni nasekugcinweni kwamandla kuyo yonke impilo yesitshalo.
Ukuthuthukisa kanye Nokuzivumelanisa Nezimo
Ijubane kanye nokusebenza kahle komjikelezo weCalvin kungahluka kuye ngezimo zemvelo ezifana nokushisa, ukuqina kokukhanya, kanye nokuhlushwa kwe-CO2. Izitshalo ziye zathuthukisa izindlela ezahlukene zokulungisa le nqubo. Isibonelo, izitshalo ze-C4 kanye ne-CAM ziye zashintsha ukuze zenze ukulungiswa kwekhabhoni ngempumelelo kakhulu ngaphansi kwezimo zemvelo ezimbi kakhulu, njengokushisa okuphezulu kanye nesomiso.
Ezitshalweni ze-C4, ukufakwa kwekhabhoni kokuqala kwenzeka kumaseli e-mesophyll, kwakha ama-asidi e-carbon angu-4 abese edluliselwa kumaseli e-bundle sheath lapho kwenzeka khona umjikelezo weCalvin. Lokhu kuguqulwa kusiza ukunciphisa ukuphefumula nge-photorespiration futhi kwandise ukusebenza kahle kwe-photosynthesis ngaphansi kwezimo zokukhanya okuphezulu kanye nokutholakala kwamanzi aphansi.
Okwamanje, izitshalo ze-CAM (Crassulacean Acid Metabolism) zenza ukusabela okumnyama ebusuku, lapho ama-stomata azo evulekile ukwamukela i-CO2. Le khabhoni igcinwa njengama-acid e-organic bese isetshenziswa emini lapho ukukhanya kutholakala khona futhi ama-stomata azo evaliwe. Lokhu kulungiswa kuvumela izitshalo ze-CAM, njenge-cacti, ukuthi zilondoloze ukusebenza kahle kwe-photosynthesis ngenkathi zinciphisa ukulahleka kwamanzi.
Ucwaningo kanye Nokusetshenziswa
Ucwaningo lwezimo ezimnyama alubalulekile nje kuphela ekuqondeni izisekelo zebhayoloji yezitshalo kodwa futhi lunemiphumela engokoqobo kwezolimo kanye ne-biotechnology. Enye yezinselele kwezolimo zanamuhla ukwandisa ukusebenza kahle kwezitshalo zokudla ukuze kuhlangatshezwane nezidingo zabantu abakhulayo emhlabeni wonke. Ngokuqonda imininingwane yezimo ezimnyama kanye nomjikelezo kaCalvin, ososayensi bangakha amasu okukhulisa ukusebenza kahle kwe-photosynthesis kanye nokukhiqiza kwezitshalo.
Enye indlela ehlolwayo ubunjiniyela bezakhi zofuzo ukuze kwethulwe izindlela ze-metabolic ezivela ezitshalweni ze-C4 ziye ezitshalweni ze-C3, okulindeleke ukuthi kwandiswe ukusebenza kahle kwamanzi ne-nitrogen futhi kuncishiswe ingozi yokuphefumula nge-photorespiration.
Ngaphezu kwalokho, ukuqonda okwengeziwe nge-enzyme ye-RuBisCO kanye nendlela esebenza ngayo kungavula amathuba okushintsha noma ukufaka esikhundleni i-enzyme ngezinhlobo ezisebenza kahle kakhulu, okungagcina kuthuthukise umkhiqizo we-photosynthesis.
Isiphetho
Ukusabela okumnyama kwe-photosynthesis kuyizinqubo eziyinkimbinkimbi ezibalulekile ekuphileni eMhlabeni. Ngomjikelezo kaCalvin, izitshalo nezinye izinto eziphilayo ezizenzakalelayo zimunca i-carbon dioxide esemkhathini bese ziyiguqula ibe yizinto eziphilayo ezibalulekile ekudleni nasemandlani. Ukuqonda nokusebenzisa izindlela zokusabela okumnyama akugcini nje ngokujulisa ukuqonda kwethu ngebhayoloji yezitshalo kodwa futhi kwenza kube lula ukuthuthuka kwezolimo kanye ne-biotechnology ukuze kube nezinzuzo ezibanzi. Ukubaluleka kokusabela okumnyama akunakuphikiswana, njengoba lezi zinqubo zingasekeli nje kuphela impilo yezitshalo kodwa nazo zonke izinhlobo zokuphila emhlabeni ezincike ezitshalweni ukuze zithole umoya-mpilo kanye nokudla. Ukusabela okumnyama kuwubufakazi obuphilayo bokuphelela nobuhle bezinqubo zemvelo ezisekela ukuphila.
