Lub neej yog txheej txheem ntawm kev muaj cov protein molecules. Qhov no yog pes tsawg tus kws tshawb fawb qhia nws, leej twg ntseeg tau tias cov protein yog lub hauv paus ntawm txhua yam muaj sia. Cov kev txiav txim siab no yog qhov tseeb tiag, vim tias cov tshuaj no hauv lub xov tooj ntawm tes muaj cov haujlwm loj tshaj plaws. Tag nrho lwm cov organic tebchaw ua lub luag haujlwm ntawm lub zog substrates, thiab lub zog rov qab xav tau rau kev sib txuas ntawm cov protein molecules.
Lub cev muaj peev xwm los tsim cov protein
Tsis yog txhua yam kab mob uas twb muaj lawm tuaj yeem tsim cov proteins hauv ib lub xovtooj ntawm tes. Cov kab mob thiab qee hom kab mob tsis tuaj yeem tsim cov protein, thiab yog li ntawd yog cov kab mob cab thiab tau txais cov khoom tsim nyog los ntawm tus tswv tsev cell. Lwm cov kab mob, suav nrog cov hlwb prokaryotic, muaj peev xwm ua kom cov proteins. Txhua tus tib neeg, tsiaj txhu, nroj tsuag, cov kab mob fungal, yuav luag tag nrho cov kab mob thiab cov protists nyob ntawm lub peev xwm ntawm cov protein biosynthesis. Qhov no yuav tsum tau siv rau kev siv cov qauv tsim, tiv thaiv, receptor, thauj thiab lwm yam haujlwm.
theem tebCov protein biosynthesis
Cov qauv ntawm cov protein yog encoded hauv nucleic acid (DNA lossis RNA) hauv daim ntawv codons. Qhov no yog cov ntaub ntawv keeb kwm uas tau tsim dua tshiab txhua lub sijhawm uas lub cell xav tau cov tshuaj protein tshiab. Qhov pib ntawm biosynthesis yog kev hloov cov ntaub ntawv mus rau lub nucleus txog kev xav tau los ua ke cov protein tshiab nrog cov khoom uas twb tau muab lawm.
Nyob rau qhov no, ib feem ntawm nucleic acid yog despiralized, qhov twg nws cov qauv yog encoded. Qhov chaw no yog duplicated los ntawm messenger RNA thiab pauv mus rau ribosomes. Lawv yog lub luag haujlwm rau kev tsim cov saw hlau polypeptide raws li matrix - messenger RNA. Luv luv, txhua theem ntawm biosynthesis tau nthuav tawm raws li hauv qab no:
- kev hloov pauv (theem ntawm ob npaug ntawm ntu DNA nrog cov qauv encoded protein);
- processing (tsim tus tub txib RNA);
- txhais lus (protein synthesis nyob rau hauv ib lub cell raws li tus tub txib RNA);
- kev hloov pauv tom qab kev hloov pauv ("kev loj hlob" ntawm polypeptide, tsim ntawm nws cov qauv peb-dimensional).
Nucleic acid transcription
Txhua cov protein synthesis hauv ib lub xovtooj yog ua los ntawm ribosomes, thiab cov ntaub ntawv hais txog cov molecules muaj nyob rau hauv nucleic acid (RNA lossis DNA). Nws nyob hauv cov noob: txhua lub noob yog cov protein tshwj xeeb. Cov noob muaj cov ntaub ntawv hais txog cov amino acid ib ntus ntawm cov protein tshiab. Nyob rau hauv rooj plaub ntawm DNA, kev tshem tawm ntawm caj ces yog ua raws li no:
- tso tawm ntawm qhov chaw nucleic acid los ntawm histones pib, despiralization tshwm sim;
- YDNA polymerasedoubles seem ntawm DNA uas khaws cov noob protein;
- ob ntu ntu yog qhov ua ntej ntawm tus xa xov RNA, uas yog ua tiav los ntawm enzymes kom tshem tawm cov ntawv tsis-coding (mRNA synthesis yog ua raws li nws lub hauv paus).
Raws li cov ntaub ntawv tshaj tawm RNA, mRNA yog tsim los. Nws twb yog ib tug matrix, tom qab uas protein synthesis nyob rau hauv lub cell tshwm sim ntawm ribosomes (nyob rau hauv lub ntxhib endoplasmic reticulum).
YRibosomal protein synthesis
Xov RNA muaj ob qhov kawg, uas tau npaj ua 3`-5`. Kev nyeem ntawv thiab kev sib txuas ntawm cov proteins ntawm ribosomes pib ntawm 5'kawg thiab txuas ntxiv mus rau intron, ib cheeb tsam uas tsis encode ib qho ntawm cov amino acids. Nws mus zoo li no:
- messenger RNA "txoj hlua" mus rau ribosome, txuas thawj cov amino acid;
- lub ribosome hloov raws tus tub txib RNA los ntawm ib codon;
- hloov RNA muab qhov xav tau (encoded los ntawm mRNA codon muab) alpha-amino acid;
- ib qho amino acid koom nrog cov amino acid pib los tsim cov dipeptide;
- ces mRNA tau hloov pauv ib codon dua, ib qho alpha amino acid tau coj los rau hauv thiab koom nrog cov saw peptide loj hlob.
Thaum lub ribosome ncav cuag lub intron (tsis yog-coding insert), tus tub txib RNA cia li txav mus. Tom qab ntawd, raws li tus neeg xa xov RNA nce mus, lub ribosome rov mus txog qhov exon - qhov chaw uas nws cov nucleotide ib ntus sib raug rau qee yam.amino acid.
Los ntawm qhov no, qhov sib ntxiv ntawm cov protein monomers rau cov saw hlau pib dua. Cov txheej txheem txuas ntxiv mus kom txog rau thaum lub intron tom ntej tshwm los yog kom txog thaum nres codon. Lub tom kawg nres qhov kev sib txuas ntawm cov saw hlau polypeptide, tom qab ntawd cov qauv tseem ceeb ntawm cov protein tau txiav txim siab ua tiav thiab theem ntawm postsynthetic (post-translational) hloov pauv ntawm cov molecule pib.
Post-translational modification
Tom qab kev txhais lus, protein synthesis tshwm sim hauv cisternae ntawm tus endoplasmic reticulum du. Cov tom kawg muaj tsawg tus ribosomes. Hauv qee lub hlwb, lawv yuav tsis tuaj yeem nyob hauv RES. Cov cheeb tsam zoo li no yuav tsum tau ua thawj zaug thib ob, tom qab ntawd lub tsev kawm qib siab lossis, yog tias programmed, tus qauv quaternary.
Txhua cov protein synthesis hauv cell tshwm sim nrog kev siv nyiaj ntau ntawm ATP lub zog. Yog li, tag nrho lwm cov txheej txheem lom neeg xav tau los tswj cov protein biosynthesis. Tsis tas li ntawd, qee lub zog xav tau rau kev hloov pauv ntawm cov protein hauv lub cell los ntawm kev thauj mus los.
Ntau cov proteins raug xa los ntawm ib qho chaw hauv cell mus rau lwm qhov kev hloov kho. Hauv particular, post-translational protein synthesis tshwm sim nyob rau hauv lub Golgi complex, qhov twg ib tug carbohydrate los yog lipid domain yog txuas mus rau ib tug polypeptide ntawm ib tug tej yam qauv.
