Indima ye-RNA ekwakhiweni kwamaphrotheni
Ukwenziwa kwamaprotheni kuyinqubo eyisisekelo evumela amangqamuzana aphilayo ukuba akhule, azilungise, futhi enze imisebenzi eyahlukahlukene yezinto eziphilayo. Ngemuva kwale nqubo, i-RNA (ribonucleic acid) idlala indima ebalulekile njengesixhumanisi phakathi kolwazi lwezakhi zofuzo olugcinwe ku-DNA kanye nokwakheka kwamaprotheni ngaphakathi kwamaseli. Ngaphandle kwe-RNA, ikhodi yezakhi zofuzo ayikwazi ukuhunyushwa ibe ama-molecule asebenzayo njengama-enzyme, ama-hormone, kanye nezingxenye zesakhiwo zamaseli. Lesi sihloko sixoxa ngendima ye-RNA ekwakhiweni kwamaprotheni, izinhlobo ze-RNA ezihilelekile, kanye nezigaba ezibalulekile zenqubo.
I-RNA njengoMthwali Wolwazi Lwezakhi Zofuzo
I-DNA igcina ulwazi lwezakhi zofuzo ngendlela yochungechunge lwezisekelo ze-nitrogen. Kodwa-ke, i-DNA itholakala ngokuyinhloko ku-nucleus yeseli (kumaseli e-eukaryotic) futhi ayisetshenziswa ngqo ukwenza amaprotheni. Yilapho i-RNA ingena khona: isebenza njengekhophi esebenzayo yolwazi lwezakhi zofuzo. Uma iqhathaniswa ne-DNA, i-RNA inomehluko obalulekile ominingana, njengokusebenzisa ushukela we-ribose, ukufaka esikhundleni se-uracil (U) nge-thymine (T), futhi ngokuvamile ihlanganiswe ngomcu owodwa. Lezi zakhiwo zenza i-RNA ibe nezimo kakhulu ekusebenzisaneni nezingxenye ezahlukene zamaseli ngesikhathi sokwenziwa kwamaprotheni.
Izinhlobo ze-RNA Ezihilelekile
Kunezinhlobo ezintathu eziyinhloko ze-RNA ezihileleke ngqo ekwakhiweni kwamaprotheni: i-mRNA, i-tRNA, kanye ne-rRNA. Zonke ezintathu zisebenza ngokubambisana ukuhumusha ulwazi oluvela ku-DNA lube yi-amino acid sequence efanele.
1. i-mRNA (i-RNA yesithunywa)
I-mRNA iyi-RNA yesithunywa. Umsebenzi wayo ukuthwala ulwazi lwezakhi zofuzo kusuka ku-DNA kuya kuma-ribosome, lapho kuhlanganiswa khona amaprotheni. I-mRNA iqukethe uchungechunge lwama-codon, angamaqembu ezisekelo ezintathu ze-nitrogen, ngalinye limelela i-amino acid noma isignali yokuma. Ngamanye amazwi, i-mRNA "iyi-script" efundwa yi-ribosomes ukuze ihlanganise amaprotheni.
Kumaseli e-eukaryotic, i-mRNA esanda kwakheka iyacutshungulwa ngaphambi kokushiya i-nucleus. Le nqubo ihlanganisa ukungezwa kwesivalo esingu-5', ukungezwa komsila we-poly-A ekugcineni okungu-3', kanye nokuxhuma ukuze kususwe ama-intron futhi kuhlanganiswe ama-exons. Lokhu kucubungula kwandisa ukuzinza kwe-mRNA futhi kuqinisekisa ukuthi ingahunyushwa kahle.
2. i-tRNA (i-RNA yokudlulisa)
I-tRNA isebenza "njengomthuthi" wama-amino acids aya ku-ribosome. I-tRNA ngayinye ine-anticodon, izisekelo ezintathu ezihambisana ne-codon ku-mRNA. Ngaphezu kwalokho, i-tRNA ithwala i-amino acid ethile ngakolunye uhlangothi lwayo. Lapho i-anticodon ihlangana ne-codon ehambisanayo ku-ribosome, i-tRNA ibeka i-amino acid eyithwalayo ku-polypeptide chain ekhulayo.
Ukunemba kwe-tRNA ekuthwaleni ama-amino acid kubalulekile. Le nqubo isizwa yi-enzyme i-aminoacyl-tRNA synthetase, "elayisha" i-tRNA ngama-amino acid afanele. Uma kwenzeka iphutha, iphrotheni ephumayo ingaba nesakhiwo nomsebenzi ohlukile.
3. i-rRNA (i-ribosomal RNA)
I-rRNA iyisici esibalulekile sama-ribosome, ama-organelle lapho kwenzeka khona ukwenziwa kwamaprotheni. Ama-ribosome akhiwa ama-rRNA nama-ribosomal protein. I-rRNA ayisebenzi nje kuphela njengohlaka lwesakhiwo sama-ribosome kodwa futhi inamakhono okulungisa izinto. Ezintweni eziningi eziphilayo, i-rRNA isebenza njenge-ribozyme, i-RNA engasheshisa ukusabela kwamakhemikhali. Ekuhlanganisweni kwamaprotheni, i-rRNA isiza ekwakhekeni kwezibopho ze-peptide phakathi kwama-amino acid, isinyathelo esibalulekile ekwakhekeni kwamaprotheni.
Isigaba Sokubhalwa: Ukwakhiwa kwe-mRNA kusuka ku-DNA
Ukwenziwa kwamaprotheni kuqala ngokubhala, inqubo yokukopisha ulwazi lwe-DNA ku-mRNA. Ukubhala kwenzeka lapho i-enzyme i-RNA polymerase inamathela ku-promoter ku-DNA, bese ikhulula i-DNA helix bese ihlanganisa uchungechunge lwe-RNA ngokusekelwe ekubhanqeni kwesisekelo okuhambisanayo. Uma i-DNA inesisekelo esingu-A, i-RNA izongeza u-U; uma i-DNA inesisekelo esingu-T, i-RNA izongeza u-A; u-C uzobhangqa no-G, futhi okuphambene nalokho.
Ukubhalwa kwe-transcription kukhiqiza i-pre-mRNA kuma-eukaryotes, bese icutshungulwa ibe yi-mRNA evuthiwe. Uma ukucubungula sekuqediwe, i-mRNA iphuma kuyi-nucleus nge-pores yenuzi bese ingena kuyi-cytoplasm, lapho kutholakala khona ama-ribosome.
Isigaba Sokuhumusha: Ukuhumusha i-mRNA ibe yiProtheni
Uma i-mRNA isiku-cytoplasm, inqubo yokuhumusha iyaqala. Ukuhumusha kwenzeka ku-ribosome futhi kunezigaba ezintathu eziyinhloko: ukuqalisa, ukunwebeka, kanye nokuphela. Ngesikhathi sesigaba sokuqalisa, i-ribosome ibona i-mRNA futhi ifune i-codon yokuqala (ngokuvamile i-AUG), ekhombisa ukuqala kokwenziwa kwamaprotheni. I-codon ye-AUG iphinde ibhale i-amino acid methionine, ngakho-ke i-methionine ivame ukuba yi-amino acid yokuqala ku-polypeptide chain.
Ngesikhathi sesigaba sokwandiswa, i-ribosome ihamba nge-mRNA, ifunda ama-codon ngayinye. I-tRNA efanele ingena kwi-ribosome, iphethe i-amino acid efanele. I-ribosome yakha isibopho se-peptide phakathi kwe-amino acid entsha kanye nochungechunge lwe-polypeptide olukhulayo. Le nqubo iyaphinda, yandise uchungechunge lwe-polypeptide ngokuya ngokulandelana kwama-codon e-mRNA.
Isigaba sokugcina ukuphela, okwenzeka lapho i-ribosome ihlangana ne-stop codon (UAA, UAG, noma i-UGA). I-stop codon ayifaki ikhodi ye-amino acid, kodwa kunalokho ikhombisa ukuphela kokuguqulwa. Izici zokuphela zisiza ekukhululeni uchungechunge lwe-polypeptide ku-ribosome. I-polypeptide ibe isigoqeka ibe yisakhiwo esinezinhlangothi ezintathu futhi ingase iguqulwe ngemva kokuguqulwa ukuze ibe yiprotheni esebenzayo.
Indima Yamanye Ama-RNA Ekulawulweni Kokwenziwa Kwamaprotheni
Ngaphezu kwe-mRNA, i-tRNA, kanye ne-rRNA, kunezinye izinhlobo ze-RNA ezidlala indima engaqondile kodwa ebalulekile ekulawuleni ukwakheka kwamaprotheni, njenge-miRNA (i-microRNA) kanye ne-siRNA (i-RNA encane ephazamisayo). Lawa ma-RNA amancane anganamathela ku-mRNA futhi avimbele ukuhumusha noma abangele ukuwohloka kwawo. Ngakho-ke, amaseli angalawula ukuthi kukhiqizwa nini futhi kungakanani iphrotheni ethile. Lo mthetho ubalulekile ekuthuthukisweni kwezinto eziphilayo, ekuphenduleni ukucindezeleka, kanye nasekuvimbeleni ukukhiqizwa kwamaprotheni okungadingekile.
Ukubaluleka kwe-RNA Empilweni
Indima ye-RNA ekwakhiweni kwamaprotheni yenza le molekyuli ibe yingxenye ebalulekile yokuphila. I-RNA ayiyona nje i-intermediary engenzi lutho, kodwa futhi ingumdlali osebenzayo, oqinisekisa ukuhunyushwa okunembile nokuphumelelayo kolwazi lwezakhi zofuzo. Ngokubambisana kwe-mRNA, ethwala imiyalezo, i-tRNA, ethwala ama-amino acid, kanye ne-rRNA, eyakha isikhungo se-catalytic sama-ribosome, amaseli akwazi ukukhiqiza amaprotheni adingekayo kuyo yonke imisebenzi yezinto eziphilayo.
Ngaphezu kwalokho, ukutholakala kwama-RNA alawulayo njenge-miRNA kwandise ukuqonda kwethu ukuthi i-RNA nayo idlala indima ekulawuleni ukuvezwa kwezakhi zofuzo, hhayi nje ukukopisha nokuhumusha ulwazi. Ku-biotechnology kanye nezokwelapha, ukuqonda i-RNA kuholele ekuthuthukisweni kwezindlela zokwelapha ezisekelwe ku-RNA, okuhlanganisa imigomo ye-mRNA kanye namasu okuthulisa izakhi zofuzo kusetshenziswa ukuphazamiseka kwe-RNA.
Isiphetho
I-RNA idlala indima ebalulekile ekwakhiweni kwamaprotheni, kusukela ekubhaleni ulwazi lwe-DNA ngokulotshwa kwemibhalo kuya ekuhumusheni ikhodi yezakhi zofuzo ngokuhumusha. I-mRNA ithwala umlayezo wezakhi zofuzo, i-tRNA iqinisekisa ukuthi ama-amino acid afanele athuthwa aye ku-ribosome, kanti i-rRNA iyisakhi sesakhiwo nesibangela ukwakheka kwe-ribosome. Ndawonye, i-RNA ivumela ukwakheka okunembile kwamaprotheni ngokwemiyalelo yezakhi zofuzo. Ngakho-ke, i-RNA ingenye yamabhuloho abalulekile phakathi kolwazi lwezakhi zofuzo nomsebenzi wezinto eziphilayo, okwenza kube yindawo ebalulekile ku-biology yamangqamuzana yanamuhla.
