Sebopeho le Mosebetsi oa Li-Ribosome
Li-ribosome ke e 'ngoe ea li-organelle tsa bohlokoa ka ho fetisisa ka har'a lisele, li bapala karolo e tobileng tlhahisong ea protheine. Liprotheine ke limolek'hule tsa mantlha tse ikarabellang bakeng sa hoo e ka bang mesebetsi eohle ea baeloji, ho tloha ho theheng meaho ea sele, ho potlakisa liketso tsa lik'hemik'hale ka li-enzyme, ho laola lipontšo tsa lisele, le ho thusa ho itšireletsa 'meleng. Ka hona, ho utloisisa sebopeho le mosebetsi oa li-ribosome ho bolela ho utloisisa e 'ngoe ea litsi tsa ts'ebetso ea bophelo boemong ba limolek'hule.
Ho utloisisa Li-Ribosome
Li-ribosome ke metsoako e meholo ea limolek'hule e entsoeng ka liprotheine tsa ribosomal RNA (rRNA) le ribosomal. Li-ribosome li fumanoa mefuta eohle ea lisele—li-prokaryotes (joalo ka libaktheria) le li-eukaryotes (joalo ka liphoofolo, limela le li-fungus). Ho ikhetha ha li-ribosome ho itšetlehile ka sebopeho sa tsona: rRNA ha se karolo ea sebopeho feela empa hape e bapala karolo ea ho susumetsa ho thehoeng ha litlamo tsa peptide. Ka mantsoe a mang, li-ribosome li ka nkoa e le "mechine" ea baeloji e fetolelang tlhahisoleseling ea liphatsa tsa lefutso ho tloha ho mRNA ho ea ho tatellano ea li-amino acid tse etsang liprotheine.
Sebopeho sa Motheo sa Li-Ribosome
Ka kakaretso, li-ribosome li na le li-subunit tse peli: subunit e nyane le subunit e kholo. Li-subunit tsena tse peli lia kopana nakong ea phetolelo (phetolelo ea mRNA) 'me lia arohana ha li sa sebetse. Subunit e 'ngoe le e 'ngoe e entsoe ka rRNA le protheine ka litekanyo tse itseng.
Li-Ribosome ka har'a Prokaryotes (70S)
Liseleng tsa prokaryotic, ho thoe li-ribosome li boholo ba 70S (S ke yuniti ea Svedberg e bontšang sekhahla sa ho senngoa ha sedimentation nakong ea ho centrifugation, eseng tekanyo e tobileng ea bolelele). Li-ribosome tsa 70S li na le:
– Karoloana e nyane ea 30S, e nang le 16S rRNA le liprotheine tse 'maloa.
– Karoloana e kgolo ya 50S, e nang le diprotheine tsa rRNA le ribosomal tsa 23S le 5S.
Karolo e nyane e bapala karolo ea bohlokoa ho lemoheng mRNA le ho fumana sebaka sa ho qala ha phetolelo, ha karolo e kholo e le sebaka se seholo sa ho thehoa ha maqhama a peptide.
Li-Ribosome ho Eukaryotes (80S)
Liseleng tsa eukaryotic, li-ribosome li boholo ba 80S, li entsoe ka:
– Karoloana e nyane ea 40S, e nang le 18S rRNA.
– Karoloana e kgolo ya 60S, e nang le rRNA ya 28S, 5.8S, le 5S.
Li-ribosome tsa eukaryotic ka kakaretso li rarahane haholo, li na le liprotheine tse ngata tsa ribosomal le lintlha tse ling tse laolang ts'ebetso ea phetolelo.
Sebaka sa Li-Ribosome ka Liseleng
Li-Ribosome li ka fumanoa libakeng tse peli tse ka sehloohong:
1. Li-ribosome tse lokolohileng ka har'a cytoplasm
Li-ribosome tse lokolohileng hangata li hlahisa liprotheine tse tla sebelisoa ka har'a cytosol, mohlala, li-enzyme tsa metabolism kapa liprotheine tsa sebopeho sa sele.
2. Li-ribosome li tlameletsoe ho rough endoplasmic reticulum (rough ER)
Li-ribosome tse hoketsoeng ho rough ER hangata li hlahisa liprotheine tse lokelang ho ntšoa ka ntle ho sele, li kenngoe ka har'a lera la sele, kapa li isoa ho li-organelle tse itseng tse kang lysosomes. Li-ribosome li hokela hobane rough ER e na le li-receptor tse sebelisanang le li-ribosomes ha ketane ea polypeptide e hlahisoang e na le lets'oao le itseng (signal peptide).
Ho phaella moo, di-organelle tse kang mitochondria le di-chloroplast le tsona di na le di-ribosome tsa tsona, tse tshwanang haholo le di-ribosome tsa prokaryotic (70S). Sena se tshehetsa kgopolo ya endosymbiosis, e bolelang hore mitochondria le di-chloroplast di simolohile ho diphedi tsa prokaryotic tse neng di phela ka ho sebedisana ka hare ho disele tsa baholoholo ba eukaryotic.
Likarolo tsa Ribosome: rRNA le Protheine
Li-Ribosome li entsoe ka likarolo tse peli tse ka sehloohong:
– Ribosomal RNA (rRNA): Ena ke mofuta o ka sehloohong oa RNA 'me e etsa moralo le setsi sa catalytic sa ribosome. rRNA e ikarabella bakeng sa ho catalyst ho thehoeng ha li-peptide bond (mosebetsi oa peptidyl transferase).
– Liprotheine tsa Ribosomal: li sebetsa ho tsitsisa sebopeho sa rRNA, li thusa ho bokella li-subunit, le ho sebelisana le lintlha tsa phetolelo.
Motsoako oa rRNA le liprotheine o etsa sebopeho se nepahetseng sa mahlakore a mararo, se lumellang li-ribosome ho sebetsa kapele le ka nepo.
Libaka tse Sebetsang ka Hare ho Li-Ribosome
Ha ribosome e fetolela ka mafolofolo, ho na le libaka tse tharo tse kholo tse bohlokoa haholo, haholo-holo karolong e kholo ea li-subunit:
1. Sebaka sa A (Sebaka sa Aminoacyl)
Sebaka sa ho kena bakeng sa tRNA e jereng li-amino acid ho latela codon ea mRNA.
2. Sebaka sa P (sebaka sa Peptidyl)
Sebaka sa tRNA e jereng ketane e ntseng e hola ea polypeptide.
3. Sebaka sa E (Sebaka sa ho Tsoa)
Sebaka seo tRNA e lokollotseng li-amino acid e tsoang ho sona.
Ho sisinyeha ha tRNA ho tloha ho A ho ea ho P ebe ho ea ho E ho etsahala ha ribosome e "bala" metheo e meraro ea mRNA ka nako e le 'ngoe (codon ka codon).
Mosebetsi oa Li-Ribosome ho Synthesis ea Protheine
Mosebetsi o ka sehloohong oa li-ribosome ke phetolelo, e fetolelang tatellano ea nucleotide ho mRNA ho tatellano ea amino acid. Phetolelo ka kakaretso e arotsoe ka mekhahlelo e meraro:
1. Letšolo
Mothating ona, karoloana e nyane ea ribosome e khomarela mRNA 'me e batla codon ea ho qala (hangata AUG). TRNA ea ho qala e jereng methionine le eona ea kopana. Hang ha codon ea ho qala e se e le teng, likaroloana tse kholo lia bokana ho etsa ribosome e sebetsang.
2. Ho lelefatsa
Ribosome e tsamaya ho pholletsa le mRNA, e atolosa ketane ya polypeptide. TRNA e jereng amino acid e kena sebakeng sa A, moo e kgomaretswang ketane sebakeng sa P. Ribosome e ntano fetola codon e le nngwe, e tlosa tRNA mme e etsa sebaka bakeng sa tRNA e latelang.
3. Pheliso
Ha ribosome e kopana le codon e emisang (UAA, UAG, kapa UGA), ha ho na tRNA e tšoanang bakeng sa codon eo. Ho e-na le hoo, ntlha ea ho felisa e kena 'me e baka ho lokolloa ha ketane ea polypeptide. Joale ribosome e arohana ho ba li-subunit tse peli 'me e se e loketse ho sebelisoa hape.
Li-Ribosome e le Lipheo tsa Lithibela-mafu
Li-ribosome tsa prokaryotic li fapana ka sebopeho ho li-ribosome tsa eukaryotic. Phapang ena e sebelisoa hampe merianeng hobane lithibela-mafu tse ling li ka thibela li-ribosome tsa baktheria ntle le ho senya li-ribosome tsa batho haholo. Mohlala:
– Tetracycline e thibela ho kena ha tRNA sebakeng sa A.
– Chloramphenicol e thibela mosebetsi oa peptidyl transferase.
– Streptomycin e ka baka ho se utloisise hantle ha mRNA.
Leha ho le jwalo, tshebediso ya dithibela-mafu e lokela ho ba e loketseng hobane dibaktheria di ka hlahisa kganyetso ka phetoho ya diphedi kapa mekgwa e meng ya ho itšireletsa.
Qetello
Li-ribosome ke li-organelle tsa bohlokoa tse sebetsang e le sebaka sa tlhahiso ea protheine. Sebopeho sa ribosome se na le li-subunit tse peli, e kholo le e nyane, 'me likarolo tse ka sehloohong ke liprotheine tsa rRNA le ribosomal. Li-ribosome li na le libaka tsa A, P, le E, tse netefatsang ts'ebetso e hlophisehileng le e nepahetseng ea phetolelo. Ntle le ho bapala karolo ea bohlokoa tlhahisong ea protheine bakeng sa litlhoko tsa sele, li-ribosome li boetse li reretsoe lithibela-mafu tse fapaneng ka lebaka la phapang lipakeng tsa li-ribosome tsa prokaryotic le eukaryotic. Ka ho utloisisa sebopeho le mosebetsi oa li-ribosome, re ka bona hore na lits'ebetso tsa motheo tse bolokang bophelo li rarahane ebile li hokahane hakae.
