Ithiyori Yokuziphendukela Kwemvelo Kwamakhemikhali: Izisekelo Zokuqonda Imvelaphi Yokuphila
Ezweni lesayensi, omunye wemibuzo eyisisekelo neyinselele ososayensi abaqhubeka befuna ukuyiphendula ukuthi impilo eMhlabeni yaqala kanjani. Omunye umbono ozama ukuchaza lesi simo "umbono wokuziphendukela kwamakhemikhali." Lo mbono uzama ukuchaza inqubo lapho ama-molecule angaphili aguquka kancane kancane abe izakhiwo eziyinkimbinkimbi futhi ekugcineni abe izinhlelo eziphilayo.
Ingemuva Lokuziphendukela Kwemvelo Kwamakhemikhali
Ngaphambi kokuhlolisisa ngokujulile, kubalulekile ukuqonda ukuthi ukuziphendukela kwamakhemikhali kuyisigaba sokuqala senqubo enkulu eyaziwa ngokuthi "i-abiogenesis" - inqubo lapho ukuphila kuvela khona ezintweni ezingaphili. Nakuba ukuziphendukela kwemvelo kwezinto eziphilayo kuchaza ukuthi izinto eziphilayo zishintsha futhi zithuthuke kanjani ezizukulwaneni ngezizukulwane, ukuziphendukela kwemvelo kwamakhemikhali ukuziphendukela kwemvelo okwenzeka ezingeni lama-molecule.
Kulinganiselwa ukuthi uMhlaba wadalwa eminyakeni engaba yizigidigidi ezingu-4,5 edlule, kanti izimpawu zokuqala zokuphila zavela eminyakeni engaba yizigidigidi ezingu-3,5–3,8 edlule. Phakathi nalesi sikhathi, izimo eMhlabeni zazihluke kakhulu kunezanamuhla. Iplanethi yayigcwele izilwandle zasendulo ezicebile ngama-molecule alula ahlukahlukene, akhishwa ngobuningi obukhulu ngezimo ezahlukahlukene ze-geological kanye ne-atmospheric.
Ithiyori ye-Oparin-Haldane
Ngawo-1920, ososayensi ababili, u-Aleksandr Oparin waseRussia no-J.B.S. Haldane waseNgilandi, bacabanga ngokuzimela ukuthi umkhathi wakudala woMhlaba wawucebile ngamagesi afana ne-methane, i-ammonia, i-hydrogen, kanye nomhwamuko wamanzi. Baphikisana ngokuthi amandla avela embaneni, emisebeni ye-UV, kanye nokushisa kwentaba-mlilo kungenzeka ukuthi kwabangela ukusabela kwamakhemikhali okwaguqula la ma-molecule alula abe ama-molecule ayinkimbinkimbi e-organic akha isisekelo sokuphila.
Lo mbono waholela ocwaningweni oludumile kakhulu ngokuziphendukela kwemvelo kwamakhemikhali, "ukuhlolwa kukaMiller-Urey," okwenziwa nguStanley Miller noHarold Urey ngo-1953. Kulolu cwaningo, balingisa izimo zomkhathi wokuqala woMhlaba futhi babonisa ngempumelelo ukuthi ama-molecule e-organic, kufaka phakathi ama-amino acid, angakheka ngokuzenzekelayo. Lo mphumela wanikeza ukwesekwa okuqinile kwenkolelo-mbono ka-Oparin-Haldane futhi wayenza yaba yitshe lesisekelo lezifundo zokuphila kwasekuqaleni.
Inqubo Yokuziphendukela Kwemvelo Kwamakhemikhali
Inqubo yokuvela kwamakhemikhali ingahlukaniswa ngezigaba eziningana ezibalulekile:
1. Ukwakheka Kwama-Molecule Alula Ezinto Eziphilayo: Ama-molecule ayisisekelo afana nama-amino acid nama-nucleotide kungenzeka ukuthi akheke ngokusabela kwamakhemikhali endaweni yakudala yoMhlaba. Ucwaningo olwengeziwe lusikisela ukuthi la ma-molecule kungenzeka ukuthi akheke nasemkhathini wangaphandle futhi alethwe eMhlabeni ngama-meteorite.
2. Ukwakheka kwe-Polymer: Ama-molecule alula e-organic angahlangana ukuze akhe ama-polymer ayinkimbinkimbi kakhulu njengama-protein nama-nucleic acid. Le nqubo ihilela ukwakheka kwe-polymer kwama-monomer abe yizakhiwo ezinde neziyinkimbinkimbi kakhulu, ezisebenza njengezitini zokwakha ama-macromolecule e-biological.
3. Ukwakheka kwe-Protobiont: Izakhiwo ezilula ezaziwa ngokuthi ama-protobiont noma ama-coacervate zingakhiwa ngala ma-polymer. Ama-Protobiont anezici eziningana zokuphila, njenge-semi-permeable membranes kanye nekhono lokwenza ukusabela okulula kwe-metabolic.
4. Isingeniso Solwazi Lwezakhi Zofuzo: Ukutholakala kwama-ribozyme, ama-molecule e-RNA angasebenza njengama-enzyme, kwasikisela ukuthi i-RNA yayiyi-molecule yokuqala eziphindaphindayo. Lokhu kwaphawula ukuqala kwekhono lezinhlelo ze-protocellular lokugcina nokukopisha ulwazi lwezakhi zofuzo.
5. Ukushintshela Ekuphileni Kwangempela: Le nqubo yayinde futhi iyinkimbinkimbi, lapho ama-molecule anekhono lokuzivuselela nokuziphindaphinda ehla ngobunzima ukuze abe izinhlelo zokuqala eziphilayo, njengamaseli e-prokaryotic.
Izinselele kanye nemibuzo engaphendulwanga
Nakuba inkolelo-mbono yokuziphendukela kwemvelo kwamakhemikhali inikeza enye yezincazelo ezinengqondo kakhulu ngemvelaphi yokuphila, kusenezinselele eziningi. Umbuzo obalulekile ukuthi la ma-molecule ayengafinyelela kanjani ubunzima obanele bokuphila. Inqubo yokwakha izakhiwo eziziphindaphindayo ezivela kuma-molecule angewona awezinto eziphilayo isengenye yezindlela ezibaluleke kakhulu ku-biology kanye ne-chemistry.
Ngaphezu kwalokho, kunezinguqulo ezahlukene zemibono mayelana nokwakheka komkhathi wasendulo woMhlaba. Abanye ososayensi bathi umkhathi wokuqala woMhlaba wawungakhiwanga ngokuphelele ngokunciphisa amagesi, njengoba kucatshangwa yi-Oparin-Haldane theory. Lokhu kuphakamisa imibuzo mayelana nokubaluleka kwemiphumela yokuhlola kaMiller-Urey kumongo wezimo zangempela eMhlabeni ngaleso sikhathi.
Izifundo ezengeziwe zifaka phakathi ucwaningo "lolwandle olujulile" olusikisela ukuthi imigodi yamanzi angaphansi kwamanzi ingahlinzeka ngendawo efanelekile yokuvela kwamakhemikhali, ikakhulukazi ngoba ihlinzeka ngezinto ezicebile kanye nezimo zokushisa ezizinzile ukuze kwenzeke ukusabela kwamakhemikhali.
Iziqondiso Zocwaningo Lwesikhathi Esizayo
Ucwaningo kulo mkhakha luyaqhubeka nokuthuthuka ngokusebenzisa ubuchwepheshe obuthuthukisiwe kanye nezindlela ezihlanganisa imikhakha eyahlukene. Ukulingisa ngekhompyutha, ukuhlolwa kwelebhu ngaphansi kwezimo zomkhathi ezahlukahlukene, kanye nokuhlola isikhala konke kube negalelo elikhulu ekuqondeni ukuthi ama-molecule ezinto eziphilayo angakheka kanjani futhi aguquke abe yizinto eziyinkimbinkimbi kakhulu.
Ososayensi babheka nangale koMhlaba ukuze bathole izinkomba ezengeziwe. Ucwaningo lwe-astrobiology lufuna ubufakazi bama-molecule e-organic kwamanye amaplanethi nezinyanga ohlelweni lwelanga, njenge-Mars, i-Enceladus, noma i-Titan. Izinto ezitholakele ezinjengalezi zinganikeza izinkomba ezengeziwe mayelana nokwenzeka kwezinqubo ezifanayo ezenzeka ngale koMhlaba.
Isiphetho
Imfundiso yokuziphendukela kwemvelo kwamakhemikhali isalokhu iyitshe lesisekelo lokuqonda imvelaphi yokuphila. Nakuba kusenemibuzo eminingi, le ndlela inikeza ukuqonda okujulile ngezinqubo zamakhemikhali ezingaba khona ezingenzeka ngaphansi kwezimo ezifanele. Ngokuthuthuka kwezobuchwepheshe kanye nokusebenzisana kwemikhakha eminingi, sisondela ekuqondeni okubanzi komunye wemibuzo emikhulu kwezesayensi: Ukuphila kwaqala kanjani? Ingabe sodwa endaweni yonke? Ukuphendula le mibuzo ngeke kuthuthukise nje ukuqonda kwethu ngokuphila eMhlabeni, kodwa futhi namathuba okuphila ngale kwalokho.
