Okwenza Utshani Bube Luhlaza—Ukuhlolisisa I-photosynthesis

“KUNGANI utshani buluhlaza?” Mhlawumbe lapho useyingane wawubuza lowo mbuzo. Ingabe yakwanelisa impendulo? Imibuzo yezingane enjengalo ingaba ejule kakhulu. Ingasibangela ukuba sibhekisise izinto zansuku zonke esizithatha kalula futhi yembule izimangaliso ezifihlekile esingakaze sicabange ukuthi zikhona.

Ukuze uqonde ukuthi yini eyenza utshani bube luhlaza, ake ucabange okuthile okungase kubonakale kungahlobene notshani. Ake ucabange ngefektri ephelele. Ifektri ephelele ingaba indawo esebenza kahle futhi okujabulisayo ukuyibuka, akunjalo? Kunokuba ingcolise, eqinisweni ifektri ephelele ibingathuthukisa indawo ezungezile ngawo kanye umsebenzi wayo. Yebo, ibingakhiqiza okuthile okuwusizo—okubaluleke kakhulu—kuwo wonke umuntu. Ifektri enjalo kufanele iwasebenzise kahle amandla. Eqinisweni, ifektri ephelele ibingasebenzisa amandla elanga, akunjalo? Ngaleyo ndlela, ibingeke idinge ukuxhunywa emandleni kagesi noma ukudilivwa kwamalahle noma uwoyela ukuze isebenze.

Ngokungangabazeki ifektri ephelele ibingasebenzisa ama-solar panel abudlula kude lé ubuchwepheshe bomuntu banamuhla. Abengasebenza ngendlela ephumelela kakhulu, angabizi, futhi abengeke abangele ukungcola kokubili lapho enziwa nalapho esetshenziswa. Nakuba ibingasebenzisa ubuchwepheshe obusezingeni eliphakeme kakhulu, ifektri ephelele ibingakwenza kalula lokho, ngaphandle kokuphazamiseka okungalindelekile, ukuphela kwamandla, noma ukulungiswa njalo okudingwa ubuchwepheshe banamuhla. Besingalindela ukuba ifektri ephelele izisebenzele yona ngokugcwele, ingadingi ukusetshenziswa umuntu. Ngempela, ibiyozilungisa yona ngokwayo, izivuselele, futhi ikwazi ngisho nokuzandisa.

Ingabe lefektri ephelele iyindaba nje eqanjiwe engokwesayensi? Ingabe iyindaba efana nokubamba utalagu? Lutho neze, ngoba lefektri ephelele ingokoqobo njengotshani ohamba phezu kwabo. Eqinisweni, iwutshani ohamba phezu kwabo, kanye nohlinzamfuku (fern) osehhovisi lakho nesihlahla esingaphandle. Eqinisweni, ifektri ephelele iyinoma yisiphi isitshalo esiluhlaza! Zishukunyiswa ukukhanya kwelanga, izitshalo eziluhlaza zisebenzisa isikhutha, amanzi namaminerali ukuze zikhiqize ukudla, ngokuqondile noma ngokungaqondile, cishe kwazo zonke izinto eziphilayo emhlabeni. Phakathi nalenqubo, zivuselela umkhathi, zisuse isikhutha bese zifaka umoya-mpilo ohlanzekile.

Sekukonke, izitshalo eziluhlaza emhlabeni zikhiqiza amathani kashukela alinganiselwa ezigidini eziyizinkulungwane ezingu-150 kuya kwezingu-400 unyaka ngamunye—okuwumkhiqizo ongaphezu kwawo wonke okhiqizwa amafektri omuntu ensimbi, ezimoto nawezinto ezihamba emkhathini ehlanganisiwe. Zikwenza lokhu ngokusebenzisa amandla elanga ukuze zikhiphe ama-athomu e-hydrogen kuma-molecule amanzi bese zihlanganisa lawo ma-athomu e-hydrogen nama-molecule esikhutha esisemoyeni, aphendule isikhutha sibe ama-carbohydrate aziwa ngokuthi ushukela. Lenqubo ephawulekayo ibizwa ngokuthi i-photosynthesis. Khona-ke izitshalo zingasebenzisa ama-molecule azo kashukela amasha ukuze zithole amandla noma zingawahlanganisa ndawonye abe isitashi ukuze agcine ukudla noma abe i-cellulose, okungokuthile okuqinile, okunemicu eyenza inxoza yesitshalo. Ake ucabange nje! Njengoba sasikhula, leso sihlahla esikhulu se-sequoia esiphakeme ngamamitha angu-90 cishe senziwa umoya, i-molecule eyodwa yesikhutha neyodwa yamanzi ngokulandelana, ezigidini ezingenakubalwa ‘zezindawo zokuhlanganisa’ ezincane okuthiwa ama-chloroplast. Kodwa kanjani?

Ukuhlola Lenqubo

Ukwenza isihlahla se-sequoia ngomoya (namanzi namaminerali ambalwa) kuyamangalisa ngempela, kodwa akuwona umlingo. Kuwumphumela wokuklama kokuhlakanipha nobuchwepheshe obuyinkimbinkimbi kakhulu kunobomuntu. Kancane kancane, ososayensi bathungatha lenqubo eyinkimbinkimbi ye-photosynthesis ukuze babone lesi simangaliso sezimangaliso sokulumbana kwamakhemikhali esenzeka lapho. Ake siyihlole kanye nabo lenqubo ewusizo cishe kuzo zonke izinto eziphilayo emhlabeni. Mhlawumbe sizoqala ukuthola impendulo embuzweni wethu othi “Kungani utshani buluhlaza?”

Asithathe isibonakhulu sethu esinokwethenjelwa, bese sihlola iqabunga elivamile. Emehlweni enyama, lonke iqabunga libonakala liluhlaza, kodwa akunjalo. Eqinisweni amangqamuzana ngamanye esitshalo esiwabona ngesibonakhulu awaluhlaza nhlobo. Kunalokho, cishe awanambala, kodwa ngalinye linamachashazi aluhlaza angaba amashumi amahlanu kuya kwayikhulu. Lamachashazi angama-chloroplast, lapho kutholakala khona i-chlorophyll eluhlaza esheshe ikuzwele ukukhanya nalapho kwenzeka khona i-photosynthesis. Kwenzekani ngaphakathi kuma-chloroplast?

I-chloroplast injengesikhwama esincane esinezinye izikhwanyana eziyizicaba, ezibizwa ngokuthi ama-thylakoid. Ekugcineni, sesiyitholile indawo lapho kunombala oluhlaza khona otshanini. Ama-molecule aluhlaza e-chlorophyll angaphezu kwama-thylakoid, hhayi ngendlela engahlelekile, kodwa ngokwamaqembu ahlelwe ngokucophelela abizwa ngokuthi ama-photosystem. Kunezinhlobo ezimbili zama-photosystem ezitshalweni eziningi eziluhlaza, ezaziwa ngokuthi i-PSI (photosystem I) ne-PSII (photosystem II). Ama-photosystem asebenza njengamaqembu akhiqizayo kuphela efektri, ngalinye elinakekela uchungechunge oluthile lwezinyathelo ze-photosynthesis.

“Udoti” Ongalahlwa

Njengoba ukukhanya kwelanga kufinyelela kuyi-thylakoid, uhele lwama-molecule e-chlorophyll ye-PSII olubizwa ngokuthi ama-light-harvesting complex lusuke selumi ngomumo. Lama-molecule adonsa ngokukhethekile ukukhanya okuthile okubomvu. Ezindaweni ezihlukahlukene kuyi-thylakoid, uhele lwe-PSI lulindele ukukhanya okunamandla athé xaxa. Ngaleso sikhathi, kokubili i-chlorophyll namanye ama-molecule, njengama-carotenoid, adonsa ukukhanya okuluhlaza okwesibhakabhaka nokunsomi.

Ngakho kungani utshani buluhlaza? Kukho konke ukukhanya okufika ezitshalweni, ukukhanya okuluhlaza njengotshani kuphela ezingakusebenzisi, ngakho yikona esikubona ngamehlo futhi okuthwetshulwa amakhamera ethu. Ake ucabange nje! Uhlaza oluntekenteke lwasentwasahlobo, kanye nohlaza lwasehlobo, lubangelwa ukukhanya ezingakudingi izitshalo kodwa esikwazisayo thina bantu! Ngokungafani nokungcola nodoti wamafektri omuntu, ‘lodoti’ owukukhanya ngokuqinisekile uba usizo lapho sibuka imfunda enhle noma ihlathi, okuqabula imiphefumulo yethu ngombala oluhlaza.

Uma sibuyela kuyi-chloroplast, uhele lwe-PSII, amandla avela engxenyeni ebomvu yokukhanya kwelanga asedluliselwe akuma-electron kuma-molecule e-chlorophyll kuze kube yilapho ekugcineni i-electron ithola amandla, noma “ishukunyiswa,” kangangokuba isuka ngokuphelele kulolu hele, igxumele kuyi-molecule eyilindele olwelwesini lwe-thylakoid. Njengomdansi oshintshashintsha abantu adansa nabo, le-electron isuka kwenye i-molecule iye kwenye njengoba kancane kancane iphelelwa amandla. Lapho amandla ayo esenciphile, isingasetshenziswa ngokuphephile esikhundleni se-electron ekwenye i-photosystem, i-PSI.—Bheka umfanekiso 1.

Ngaleso sikhathi, uhele lwe-PSII alusenayo i-electron, okwenza lulungele futhi lulangazelele i-electron ezothatha isikhundla salena elahlekile. Njengomuntu osanda kuqaphela ukuthi ukhuthuziwe, indawo ye-PSII eyaziwa ngokuthi i-oxygen-evolving complex ivukwa amadlingozi. Izotholakalaphi i-electron? Nakho-ke! Eduzane kune-molecule yamanzi ezihambelayo nje. Izozithola isisenkingeni.

Ukuhlukanisa Ama-molecule Amanzi

I-molecule yamanzi ine-athomu lomoya-mpilo elikhulu kanye namabili amancane e-hydrogen. I-oxygen-evolving complex ye-PSII inama-ion amane e-manganese esansimbi akhipha ama-electron kuma-athomu e-hydrogen akuyi-molecule yamanzi. Umphumela uba ukuthi i-molecule yamanzi ihlukana ibe izingcezu ezimbili ezinozibuthe zama-ion e-hydrogen (protons), i-athomu elilodwa lomoya-mpilo, nama-electron amabili. Njengoba kuhlukaniswa ama-molecule amanzi engeziwe, ama-athomu omoya-mpilo ayahlangana abe ama-molecule omoya-mpilo, izitshalo eziwubuyisela emoyeni ukuze siwusebenzise. Ama-ion e-hydrogen anqwabelana ngaphakathi “esikhwameni” se-thylakoid, lapho esetshenziswa khona isitshalo, futhi ama-electron asetshenziselwa ukuphinde asekele uxhaxha oluyinkimbinkimbi lwe-PSII, manje esikulungele ukuphinda lomjikelezo izikhathi eziningi ngomzuzwana.—Bheka umfanekiso 2.

Ngaphakathi esikhwameni se-thylakoid, ama-ion e-hydrogen anqwabelene aqala ukufuna indlela yokuphuma. Akunezelwa ama-ion amabili e-hydrogen kuphela ngaso sonke isikhathi lapho ama-molecule amanzi ehlukaniswa kodwa amanye ama-ion e-hydrogen adonselwa esikhwameni se-thylakoid ama-electron e-PSII njengoba edlulela oxhaxheni lwe-PSI. Ngokushesha, ama-ion e-hydrogen aphithizela njengezinyosi ezithukuthele esidlekeni sazo esiminyene. Angaphuma kanjani?

UMklami ohlakaniphile we-photosynthesis uye walungiselela umnyango ojikelezayo onendlela eyodwa kuphela yokuphuma, oyi-enzyme ekhethekile esetshenziselwa ukukhiqiza amandla abaluleke kakhulu emangqamuzaneni athiwa i-ATP (adenosine triphosphate). Njengoba ama-ion e-hydrogen ephuma ngenkani kulomnyango ojikelezayo, anikeza amandla okuvuselela ama-molecule e-ATP asetshenzisiwe. (Bheka umfanekiso 3.) Ama-molecule e-ATP anjengamabhethri amancane. Anikeza amandla ngokushesha, ngaso kanye leso sikhathi, kuzo zonke izinqubo engqamuzaneni. Kamuva, lama-molecule e-ATP azodingeka lapho kwenziwa ushukela enqubweni ye-photosynthesis.

Ngaphandle kwe-ATP, kudingeka enye i-molecule encane lapho kwenziwa ushukela. Ibizwa ngokuthi i-NADPH (isifushaniso segama elithi nicotinamide adenine dinucleotide phosphate). Ama-molecule e-NADPH anjengamaloli amancane okudiliva, ngayinye eyisa i-athomu ye-hydrogen kuyi-enzyme elindile edinga usizo lwe-athomu ye-hydrogen ukuze yenze i-molecule kashukela. Ukwenza i-NADPH kuwumsebenzi woxhaxha lwe-PSI. Ngesikhathi enye i-photosystem (PSII) imatasa ihlukanisa ama-molecule amanzi futhi iwasebenzisa ukuze yenze i-ATP, enye i-photosystem (PSI) idonsa ukukhanya futhi ikhiphe ama-electron ekugcineni asetshenziselwa ukwenza i-NADPH. Ama-molecule e-ATP nawe-NADPH agcinwa esikhaleni esingaphandle kwe-thylakoid ukuze asetshenziswe esikhathini esizayo lapho kukhiqizwa ushukela.

Ukusebenza Ebusuku

I-photosynthesis yenza izigidi zezinkulungwane zamathani kashukela unyaka ngamunye, nokho eqinisweni ukuhlangana kwamakhemikhali okukhanya kuyi-photosynthesis akuwenzi ushukela. Kwenza kuphela i-ATP (“amabhethri”) ne-NADPH (“amaloli okudiliva”). Kuleli qophelo, ama-enzyme akuyi-stroma, noma esikhaleni esingaphandle kwama-thylakoid, asebenzisa i-ATP ne-NADPH ukuze enze ushukela. Eqinisweni, isitshalo singenza ushukela ngisho kumnyama bhuqe! Ungase ufanise i-chloroplast nefektri enamaqembu amabili ezisebenzi (i-PSI ne-PSII) ngaphakathi kuma-thylakoid enza amabhethri namaloli okudiliva (i-ATP ne-NADPH) ukuze kusetshenziswe iqembu lesithathu lezisebenzi (ama-enzyme akhethekile) akuyi-stroma. (Bheka umfanekiso 4.) Lelo qembu lesithathu lezisebenzi lenza ushukela ngokunezela ama-athomu e-hydrogen nama-molecule esikhutha ngokulandelana okunembile kokulumbana kwamakhemikhali lisebenzisa ama-enzyme akuyi-stroma. Womathathu lamaqembu angasebenza phakathi nemini, kanti iqembu elenza ushukela liyasebenza nasebusuku, okungenani kuze kube yilapho sekusetshenzisiwe okwenziwe i-ATP ne-NADPH emini.

Ungase ucabange nge-stroma njengohlobo lwesikhungo sokuxhumanisa amangqamuzana, esigcwele ama-athomu nama-molecule okudingeka “ashadiswe” kodwa angeke azihlanganele wona ngokwawo. Ama-enzyme athile anjengabaxhumanisi abaphoqelelayo.a Angama-molecule amaprotheni akhiwe ngezindlela ezikhethekile eziwavumela ukuba agxavule ama-athomu noma ama-molecule afanelekile ngenjongo ethile. Nokho, awaneliswa nje ukuhlanganisa ama-molecule azobhangqana esikhathini esizayo. Ama-enzyme awaneliswa kuze kube yilapho esehlanganisiwe, ngakho abamba umbhangqwana wesikhathi esizayo futhi asondeze abangane abamadolonzima ndawonye, aphoqelele umshado oyisigubhukane phakathi kokulumbana kwamakhemikhali. Ngemva kwalomkhosi, ama-enzyme akhipha i-molecule entsha abese enza lenqubo ngokuphindaphindiwe. Kuyi-stroma ama-enzyme adlulisa ama-molecule kashukela asecishe aphele ngesivinini esikhulu, aphinde awahlele, awanikeze amandla nge-ATP, anezele isikhutha, afake i-hydrogen, bese kuthi ekugcineni, athumele ushukela onama-carbon amathathu ukuze uyoshintshwa ndawana-thile engqamuzaneni ube i-glucose nezinye izinto eziningi ezihlukahlukene.—Bheka umfanekiso 5.

Kungani Utshani Buluhlaza?

I-photosynthesis ingaphezu kokuba ukuhlangana kwamakhemikhali okuyisisekelo. Iwukulumbana kwamakhemikhali okuhlangene okuyinkimbinkimbi ngendlela emangalisayo futhi okuwubuhlakani. Incwadi ethi Life Processes of Plants ikubeka ngalendlela: “I-photosynthesis iyinqubo ephawulekayo, eqondiswa ngezinga eliphakeme yokusetshenziswa kokukhanya kwelanga. Ukuklanywa okuyinkimbinkimbi kwezitshalo nokuqondiswa kokulumbana kwamakhemikhali nezakhi zofuzo okumangalisayo okuqondisa inqubo ye-photosynthesis kungase kubhekwe njengokuthuthukiswa kwenqubo eyisisekelo yokudonsa ukukhanya bese kuphendulwa amandla ako abe amakhemikhali.”

Ngamanye amazwi, ukuthola ukuthi yini eyenza utshani bube luhlaza kuwukubheka umklamo oyisimangaliso nobuchwepheshe obungaphezu kwanoma yini umuntu ake wayiklama—“imishini” ezilawulayo, ezilungisayo, emincane kakhulu esebenza ngemijikelezo eyizinkulungwane, noma ngisho eyizigidi, ngomzuzwana (ngaphandle kokuba nomsindo, ukungcolisa, noma ububi), ephendula ukukhanya kwelanga kube ushukela. Lokhu kusinikeza umbono ngomklami nonjiniyela wezinga eliphakeme—uMdali wethu, uJehova uNkulunkulu. Esikhathini esizayo lapho ujabulela enye “yamafektri aphelele” kaJehova amahle, asekela ukuphila, noma lapho uhamba nje otshanini obuthandekayo obuluhlaza, cabanga ngalokhu.

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[Umthombo Wesithombe ekhasini 18]

Inset photo: Colorpix, Godo-Foto

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I-“photosynthesis” yasikhulisa kanjani lesi sihlahla?

[Umdwebo ekhasini 20]

Umfanekiso 1

[Umdwebo ekhasini 20]

Umfanekiso 2

[Umdwebo ekhasini 21]

Umfanekiso 3

[Umdwebo ekhasini 21]

Umfanekiso 4

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Umfanekiso 5