Molecular biology cuam tshuam nrog kev kawm txog cov qauv thiab kev ua haujlwm ntawm cov molecules ntawm cov organic tshuaj uas tsim cov cell nyob ntawm cov nroj tsuag, tsiaj txhu thiab tib neeg. Ib qho chaw tshwj xeeb ntawm lawv yog muab rau ib pawg ntawm cov tshuaj hu ua nucleic (nuclear) acids.
Muaj ob hom: deoxyribonucleic acid (DNA) thiab ribonucleic acid. Cov tom kawg muaj ntau qhov kev hloov kho: i-RNA, t-RNA thiab r-RNA, uas txawv ntawm lawv txoj haujlwm thiab qhov chaw nyob hauv lub cell. Kab lus no tau mob siab rau txoj kev kawm ntawm cov lus nug hauv qab no: qhov twg rRNA synthesized hauv prokaryotic thiab eukaryotic hlwb, nws cov qauv thiab qhov tseem ceeb yog dab tsi.
keeb kwm keeb kwm
Thawj qhov kev tshawb fawb hais txog ribosomal acid tuaj yeem pom nyob rau hauv kev tshawb fawb ntawm R. Weinberg thiab S. Penman hauv 60s ntawm lub xyoo pua XX, uas tau piav qhia luv luv polynucleotide molecules ntsig txog ribonucleic acids, tab sis txawv ntawm cov qauv spatial thiab sedimentation coefficient los ntawm cov ntaub ntawv thiab thauj RNA. Feem ntau, lawv cov moleculespom nyob rau hauv lub nucleolus, nrog rau hauv cell organelles - ribosomes lub luag hauj lwm rau lub synthesis ntawm cellular protein. Lawv hu ua ribosomal (ribosomal ribonucleic acids).
RNA yam ntxwv
Ribonucleic acid, zoo li DNA, yog cov polymer, cov monomers uas yog nucleotides ntawm 4 hom: adenine, guanine, uracil thiab cytidine, txuas los ntawm phosphodiester bonds rau hauv ib leeg-stranded molecules ntev, twisted nyob rau hauv daim ntawv ntawm ib tug kauv los yog muaj ntau txoj kev sib haum xeeb. Tseem muaj ob-stranded ribosomal ribonucleic acids pom nyob rau hauv RNA-muaj cov kab mob thiab duplicating lub luag hauj lwm ntawm DNA: kev txuag thiab kis tau tus kab mob ntawm noob neej.
Peb hom acids feem ntau nyob hauv lub cell, cov no yog: matrix, lossis cov ntaub ntawv, RNA, thauj ribosomal ribonucleic acid, uas cov amino acids txuas nrog, nrog rau ribosomal acid, nyob rau hauv nucleolus thiab cell. cytoplasm.
Ribosomal RNA ua rau kwv yees li 80% ntawm tag nrho cov nyiaj ntawm ribonucleic acids nyob rau hauv lub cell thiab 60% ntawm cov loj ntawm ribosome, ib tug organoid uas synthesizes cellular protein. Tag nrho cov hom saum toj no yog synthesized (transcribed) ntawm qee ntu ntawm DNA, hu ua RNA noob. Nyob rau hauv tus txheej txheem ntawm synthesis, molecules ntawm ib tug tshwj xeeb enzyme, RNA polymerase, koom nrog. Qhov chaw nyob rau hauv lub cell uas rRNA yog synthesized yog lub nucleolus, nyob rau hauv lub karyoplasmkernels.
Nucleolus, nws lub luag haujlwm hauv kev sib txuas
Hauv lub neej ntawm lub xovtooj ntawm tes, hu ua lub voj voog ntawm tes, muaj lub sijhawm ntawm nws qhov kev faib - interphase. Nyob rau lub sijhawm no, lub cev ntom ntom ntawm cov qauv granular, hu ua Nucleoli, yog pom meej hauv lub cell nucleus, uas yog qhov tsis tseem ceeb ntawm ob qho tib si cog thiab tsiaj hlwb.
Nyob rau hauv molecular biology, nws tau raug tsim los hais tias cov nucleoli yog cov organelles uas rRNA yog synthesized. Kev tshawb fawb ntxiv los ntawm cytologists coj mus rau kev tshawb pom ntawm ntu ntawm cellular DNA, uas cov noob muaj lub luag haujlwm rau cov qauv thiab kev sib txuas ntawm ribosomal acids tau pom. Lawv hu ua nucleolar organizer.
Nuclear organizer
Txog txog 60s ntawm lub xyoo pua XX, muaj kev xav hauv biology tias cov nucleolar organizer, nyob rau ntawm qhov chaw ntawm lub thib ob constriction nyob rau hauv lub 13th, 14, 15th, 21st thiab 22nd khub ntawm chromosomes, muaj daim ntawv. ntawm ib qhov chaw. Cov kws tshawb fawb koom nrog hauv kev tshawb fawb txog kev puas tsuaj chromosomal, hu ua aberrations, tau pom tias thaum lub sijhawm chromosome tawg ntawm qhov chaw ntawm qhov chaw thib ob, kev tsim ntawm nucleoli tshwm sim ntawm txhua qhov ntawm nws qhov chaw.
Yog li, peb tuaj yeem hais cov hauv qab no: lub nucleolar organizer tsis yog ib qho, tab sis ntawm ob peb loci (genes) lub luag haujlwm rau kev tsim cov nucleolus. Nws yog nyob rau hauv nws tias ribosomal ribonucleic acids rRNA yog synthesized, uas tsim subunits ntawm protein-synthesizing cell organelles - ribosomes.
ribosomes yog dab tsi?
Raws li tau hais ua ntej, tag nrho peb hom tseem ceebRNA muaj nyob rau hauv lub xovtooj ntawm tes, qhov chaw uas lawv yog synthesized ntawm tej chaw - DNA noob. Lub ribosomal RNA tsim los ntawm kev hloov pauv daim ntawv complexes nrog cov proteins - ribonucleoproteins, los ntawm cov khoom siv ntawm lub neej yav tom ntej organelle, lub npe hu ua subunits, tsim. Los ntawm cov pores nyob rau hauv daim nyias nyias, lawv nkag mus rau hauv lub cytoplasm thiab tsim nyob rau hauv nws cov qauv ua ke, uas kuj muaj xws li molecules ntawm i-RNA thiab t-RNA, hu ua polysomes.
Cov ribosomes lawv tus kheej tuaj yeem sib cais raws li kev ua ntawm calcium ions thiab muaj nyob nyias raws li subunits. Cov txheej txheem rov qab tshwm sim nyob rau hauv lub compartments ntawm lub cell cytoplasm, qhov twg cov txheej txheem ntawm kev txhais lus tshwm sim - lub rooj sib txoos ntawm cellular protein molecules. Qhov ntau active lub cell, qhov ntau khaus cov txheej txheem metabolic nyob rau hauv nws, ntau ribosomes nws muaj. Piv txwv li, cov hlwb ntawm cov pob txha liab, hepatocytes ntawm vertebrates thiab tib neeg yog tus cwj pwm los ntawm ntau cov organelles hauv cytoplasm.
rRNA noob encoded li cas?
Raws li cov saum toj no, cov qauv, hom thiab kev ua haujlwm ntawm rRNA noob nyob ntawm seb cov neeg ua haujlwm nucleolar. Lawv muaj loci uas muaj cov noob encoding ribosomal RNA. O. Miller, ua kev tshawb fawb txog oogenesis hauv cov hlwb tshiab, tsim cov txheej txheem ntawm kev ua haujlwm ntawm cov noob no. Cov ntawv theej ntawm rRNA (lub npe hu ua cov ntawv sau thawj zaug) tau tsim los ntawm lawv, muaj txog 13x103 nucleotides thiab muaj cov coefficient ntawm sedimentation ntawm 45 S. Ces cov saw no tau ua tiav txoj kev loj hlob, xaus nrog kev tsim ntawm peb.rRNA molecules nrog sedimentation coefficients ntawm 5, 8 S, 28 S, thiab 18 S.
Mechanism of rRNA formation
Cia peb rov qab mus rau qhov kev sim ntawm Miller, uas tau tshawb xyuas cov synthesis ntawm ribosomal RNA thiab ua pov thawj tias nucleolar DNA ua tus qauv (matrix) rau kev tsim ntawm rRNA - ib daim ntawv teev lus. Nws kuj tau tsim tias tus naj npawb ntawm cov ribosomal acids tsis paub qab hau (pre-r-RNA) uas tau tsim nyob ntawm tus naj npawb ntawm cov molecules ntawm RNA polymerase enzyme. Ces lawv maturation (processing) tshwm sim, thiab rRNA molecules tam sim ntawd pib khi rau peptides, uas ua rau tsim ib tug ribonucleoprotein, lub tsev cov ntaub ntawv ntawm lub ribosome.
Ntawm ntawm ribosomal acids hauv eukaryotic hlwb
Muaj tib lub hauv paus ntsiab lus ntawm cov qauv thiab cov txheej txheem ua haujlwm, cov ribosomes ntawm prokaryotic thiab nuclear kab mob tseem muaj qhov sib txawv cytomolecular. Txhawm rau kom paub, cov kws tshawb fawb tau siv txoj kev tshawb fawb hu ua x-ray diffraction tsom xam. Nws tau pom tias qhov luaj li cas ntawm eukaryotic ribosome, thiab li no cov rRNA suav nrog nws, yog loj dua thiab cov sedimentation coefficient yog 80 S. Cov organelle, poob magnesium ions, yuav muab faib ua ob subunits nrog ntsuas ntawm 60 S thiab 40 S.. Ib qho me me muaj ib qho molecule ntawm cov kua qaub, thiab ib qho loj - peb, uas yog, cov hlwb muaj ribosomes uas muaj 4 polynucleotide helices ntawm cov kua qaub ntawm cov yam ntxwv hauv qab no: 28 S RNA - 5 txhiab nucleotides, 18 S - 2 txhiab 5. S - 120 nucleotides, 5, 8 S - 160. Qhov chaw uas rRNA yog synthesized nyob rau hauv eukaryotic hlwb yog cov nucleolus, nyob rau hauv lub karyoplasm ntawm lub nucleus.
Ribosomal RNA ntawm prokaryotes
Unlike r-RNA,nkag mus rau hauv lub hlwb, cov ribosomal ribonucleic acids ntawm cov kab mob yog transcribed nyob rau hauv ib tug compacted cheeb tsam ntawm lub cytoplasm uas muaj DNA thiab hu ua nucleoid. Nws muaj rRNA noob. Kev hloov pauv, cov yam ntxwv dav dav uas tuaj yeem sawv cev raws li tus txheej txheem ntawm kev sau cov ntaub ntawv los ntawm rRNA ntawm DNA cov noob rau hauv cov kab ke nucleotide ntawm ribosomal ribonucleic acid, coj mus rau hauv tus account txoj cai ntawm complementarity ntawm cov noob caj noob ces: adenine nucleoitide sib raug rau uracil, thiab guanine. rau cytosine.
R-RNA cov kab mob muaj qhov hnyav dua molecular thiab me me dua li ntawm cov hlwb nuclear. Lawv cov sedimentation coefficient yog 70 S, thiab ob lub subunits muaj nuj nqis ntawm 50 S thiab 30 S. Cov khoom me me muaj ib qho rRNA molecule, thiab qhov loj dua muaj ob.
Lub luag haujlwm ntawm ribonucleic acid hauv txheej txheem txhais lus
Lub luag haujlwm tseem ceeb ntawm r-RNA yog los xyuas kom meej cov txheej txheem ntawm cellular protein biosynthesis - txhais. Nws yog nqa tawm tsuas yog nyob rau hauv lub xub ntiag ntawm ribosomes uas muaj r-RNA. Ua ke rau hauv pab pawg, lawv khi rau cov ntaub ntawv DNA molecule, tsim ib lub polysome. Molecules ntawm thauj ribosomal ribonucleic acid, nqa cov amino acids, uas, ib zaug nyob rau hauv lub polysome, khi rau ib leeg los ntawm peptide bonds, tsim ib tug polymer - protein. Nws yog qhov tseem ceeb tshaj plaws ntawm cov organic compound ntawm tes, uas ua tau ntau yam tseem ceeb: lub tsev, thauj, lub zog, enzymatic, tiv thaiv thiab signaling.
Kab lus no tau tshuaj xyuas cov yam ntxwv, qauv thiab piav qhia ntawm ribosomal nucleic acids, uas yogorganic biopolymers ntawm cov nroj tsuag, tsiaj txhu thiab tib neeg hlwb.
