Txhua lub neej hauv ntiaj teb muaj ntau lub hlwb uas tswj hwm lawv lub koom haum vim yog cov ntaub ntawv caj ces muaj nyob hauv cov nucleus. Nws yog khaws cia, siv thiab kis tau los ntawm cov complex high-molecular compounds - nucleic acids, muaj xws li monomer units - nucleotides. Lub luag hauj lwm ntawm nucleic acids tsis tuaj yeem overestimated. Kev ruaj ntseg ntawm lawv cov qauv txiav txim siab qhov kev ua haujlwm tseem ceeb ntawm lub cev, thiab txhua qhov sib txawv ntawm cov qauv yuav ua rau muaj kev hloov pauv hauv lub koom haum ntawm tes, kev ua haujlwm ntawm cov txheej txheem physiological thiab kev muaj peev xwm ntawm cov hlwb tag nrho.
Lub tswvyim ntawm nucleotide thiab nws cov khoom
Txhua lub molecule ntawm DNA lossis RNA yog sib sau los ntawm cov sib txuas me me monomeric - nucleotides. Hauv lwm lo lus, nucleotide yog cov khoom siv hauv tsev rau nucleic acids, coenzymes thiab ntau lwm cov tshuaj lom neeg uas yog qhov tseem ceeb rau lub cell hauv nws lub neej.
Rau cov khoom tseem ceeb ntawm cov irreplaceableCov tshuaj tuaj yeem raug ntaus nqi:
• khaws cov ntaub ntawv hais txog cov qauv protein thiab cov khoom qub qub;
• tswj kev loj hlob thiab kev loj hlob;
• kev koom tes hauv cov metabolism thiab ntau lwm cov txheej txheem physiological tshwm sim hauv cell.
Nucleotide muaj pes tsawg leeg
Hais txog nucleotides, ib tus tsis tuaj yeem tab sis nyob ntawm qhov teeb meem tseem ceeb xws li lawv cov qauv thiab kev sib xyaw.
Txhua nucleotide muaj:
• qab zib residue;
• nitrogenous puag;
• phosphate pawg lossis phosphoric acid residue.
Nws tuaj yeem hais tau tias nucleotide yog cov organic sib xyaw ua ke. Nyob ntawm cov tsiaj muaj pes tsawg leeg ntawm nitrogenous bases thiab hom pentose nyob rau hauv cov qauv nucleotide, nucleic acids muab faib ua:
• deoxyribonucleic acid, lossis DNA;
• ribonucleic acid, lossis RNA.
YComposition ntawm nucleic acids
Nyob rau hauv nucleic acids, qab zib yog sawv cev los ntawm pentose. Qhov no yog tsib-carbon qab zib, hauv DNA nws hu ua deoxyribose, hauv RNA nws hu ua ribose. Txhua pentose molecule muaj tsib carbon atoms, plaub ntawm uas, ua ke nrog ib tug oxygen atom, tsim ib tug tsib-ntiv nplhaib, thiab lub thib tsib yog ib feem ntawm HO-CH2 pawg.
Txoj haujlwm ntawm txhua cov pa roj carbon atom hauv pentose molecule yog qhia los ntawm tus lej Arabic nrog tus prime (1C´, 2C´, 3C´, 4C´, 5C´). Txij li thaum tag nrho cov txheej txheem ntawm kev nyeem cov ntaub ntawv keeb kwm los ntawm nucleic acid molecule muaj cov kev taw qhia nruj, cov naj npawb ntawm cov pa roj carbon atoms thiab lawv cov kev npaj nyob rau hauv lub nplhaib yog ib hom kev taw qhia ntawm txoj cai.
Raws li pawg hydroxyl rauphosphoric acid residue yog txuas rau peb thiab tsib carbon atoms (3С' thiab 5С'). Nws txiav txim siab cov tshuaj muaj feem cuam tshuam ntawm DNA thiab RNA rau pawg acids.
A nitrogenous puag yog txuas rau thawj carbon atom (1С´) hauv qab zib molecule.
Ntshai muaj pes tsawg leeg ntawm nitrogenous bases
DNA nucleotides los ntawm nitrogenous puag yog sawv cev los ntawm plaub hom:
• adenine (A);
• guanine (G);
• cytosine (C);
• thymine (T).
Thawj ob yog purines, ob lub xeem yog pyrimidines. Los ntawm qhov hnyav molecular, purines ib txwm hnyav dua pyrimidines.
RNA nucleotides los ntawm nitrogenous puag yog sawv cev los ntawm:
• adenine (A);
• guanine (G);
• cytosine (C);
• uracil (U).
Uracil, zoo li thymine, yog pyrimidine puag.
Hauv cov ntaub ntawv tshawb fawb, feem ntau tuaj yeem pom lwm qhov kev xaiv ntawm nitrogenous hauv paus - hauv Latin ntawv (A, T, C, G, U).
Cia peb nyob hauv kev nthuav dav ntxiv ntawm cov qauv tshuaj purines thiab pyrimidines.
Pyrimidines, uas yog cytosine, thymine thiab uracil, yog sawv cev los ntawm ob lub nitrogen atoms thiab plaub carbon atoms, tsim ib lub nplhaib rau-tus tswv cuab. Txhua lub atom muaj nws tus lej ntawm 1 txog 6.
Purines (adenine thiab guanine) muaj pyrimidine thiab imidazole lossis ob heterocycles. Lub purine puag molecule yog sawv cev los ntawm plaub nitrogen atoms thiab tsib carbon atoms. Txhua lub atom raug suav los ntawm 1 txog 9.
Raws li kev sib txuas ntawm nitrogenouslub hauv paus thiab pentose residue tsim ib nucleoside. Ib qho nucleotide yog kev sib xyaw ntawm nucleoside thiab pawg phosphate.
Tsim cov phosphodiester bonds
Nws yog ib qho tseem ceeb kom nkag siab txog cov lus nug ntawm yuav ua li cas nucleotides txuas nrog hauv cov saw hlau polypeptide thiab tsim cov nucleic acid molecule. Qhov no tshwm sim vim yog lub npe hu ua phosphodiester bonds.
Kev sib cuam tshuam ntawm ob nucleotides muab ib dinucleotide. Kev tsim ntawm ib qho kev sib xyaw tshiab tshwm sim los ntawm kev sib xyaw ua ke, thaum phosphodiester daim ntawv cog lus tshwm sim ntawm phosphate residue ntawm ib monomer thiab hydroxy pawg ntawm pentose ntawm lwm tus.
Synthesis ntawm polynucleotide yog rov ua dua ntawm cov tshuaj tiv thaiv no (ntau lab zaus). Cov saw hlau polynucleotide yog tsim los ntawm kev tsim cov phosphodiester bonds ntawm qhov thib peb thiab thib tsib carbons ntawm cov suab thaj (3С´ thiab 5С´).
Polynucleotide sib dhos yog cov txheej txheem nyuaj uas tshwm sim nrog kev koom tes ntawm DNA polymerase enzyme, uas ua kom txoj kev loj hlob ntawm cov saw tsuas yog los ntawm ib kawg (3') nrog pab pawg hydroxy dawb.
qauv ntawm DNA molecule
A DNA molecule, zoo li cov protein, tuaj yeem muaj cov qauv thawj, theem nrab thiab theem nrab.
Qhov sib lawv liag ntawm nucleotides hauv DNA saws txiav txim siab nws cov qauv tseem ceeb. Cov qauv theem nrab yog tsim los ntawm hydrogen bonds, uas yog raws li lub hauv paus ntsiab lus ntawm complementarity. Hauv lwm lo lus, thaum lub sij hawm kev sib txuas ntawm DNA ob lub helix, ib qho qauv ua haujlwm: adenine ntawm ib txoj saw sib raug rau thymine ntawm lwm tus, guanine rau cytosine, thiab vice versa. Ua ke ntawm adenine thiab thymine los yog guanine thiab cytosineyog tsim los ntawm ob hauv thawj thiab peb nyob rau hauv rooj plaub kawg hydrogen bonds. Xws li kev sib txuas ntawm nucleotides muab kev sib raug zoo ntawm cov chains thiab qhov sib npaug ntawm lawv.
Paub qhov nucleotide ib ntus ntawm ib DNA strand, koj tuaj yeem ua tiav qhov thib ob los ntawm lub hauv paus ntsiab lus ntawm complementarity lossis ntxiv.
Cov qauv tertiary ntawm DNA yog tsim los ntawm kev sib txuas ntawm peb sab, uas ua rau nws cov molecule ntau compact thiab muaj peev xwm haum rau hauv ib qho me me ntawm tes. Yog li, piv txwv li, qhov ntev ntawm E. coli DNA yog ntau dua 1 hli, thaum lub sijhawm ntev ntawm lub xov tooj ntawm tes yog tsawg dua 5 microns.
Tus naj npawb ntawm nucleotides hauv DNA, uas yog lawv qhov sib piv ntau, ua raws txoj cai Chergaff (tus naj npawb ntawm cov hauv paus purine ib txwm sib npaug rau cov pyrimidine hauv paus). Qhov kev ncua deb ntawm nucleotides yog tus nqi tas li sib npaug rau 0.34 nm, raws li lawv qhov hnyav molecular.
Tus qauv ntawm RNA molecule
RNA yog sawv cev los ntawm ib leeg polynucleotide saw tsim los ntawm covalent bonds ntawm pentose (qhov no, ribose) thiab phosphate residue. Nws yog luv dua DNA nyob rau hauv ntev. Kuj tseem muaj qhov sib txawv ntawm hom muaj pes tsawg leeg ntawm nitrogenous hauv paus hauv nucleotide. Hauv RNA, uracil yog siv los ntawm pyrimidine puag ntawm thymine. Raws li kev ua haujlwm hauv lub cev, RNA tuaj yeem yog peb hom.
• Ribosomal (rRNA) - feem ntau muaj los ntawm 3000 txog 5000 nucleotides. Raws li cov qauv tsim nyog, nws koom nrog hauv kev tsim cov active centre ntawm ribosomes, qhov chaw ntawm ib qho ntawm cov txheej txheem tseem ceeb tshaj plaws hauv lub cell.- protein biosynthesis.
• Thauj (tRNA) - muaj qhov nruab nrab ntawm 75 - 95 nucleotides, hloov cov amino acid uas xav tau mus rau qhov chaw ntawm polypeptide synthesis hauv ribosome. Txhua hom tRNA (tsawg kawg 40) muaj nws tus kheej ib ntus ntawm monomers lossis nucleotides.
• Cov Lus Qhia (mRNA) - muaj ntau haiv neeg hauv nucleotide muaj pes tsawg leeg. Hloov cov ntaub ntawv caj ces los ntawm DNA mus rau ribosomes, ua raws li matrix rau kev sib txuas ntawm cov protein molecule.
YLub luag haujlwm ntawm nucleotides hauv lub cev
Nucleotides hauv cell ua ntau lub luag haujlwm tseem ceeb:
• yog siv los ua lub tsev thaiv rau nucleic acids (nucleotides ntawm purine thiab pyrimidine series);
• koom nrog ntau cov txheej txheem metabolic hauv cell;
• yog ib feem ntawm ATP - lub hauv paus tseem ceeb ntawm lub zog hauv hlwb;
• ua cov nqa ntawm kev txo qis sib npaug hauv cov hlwb (NAD +, NADP +, FAD, FMN);
• ua haujlwm ntawm bioregulators;
• tuaj yeem suav hais tias yog tus xa xov thib ob ntawm cov khoom siv hluav taws xob tsis tu ncua (piv txwv li, cAMP lossis cGMP).
Nucleotide yog chav tsev monomeric uas tsim cov tshuaj sib xyaw ua ke ntau dua - nucleic acids, yam tsis muaj kev hloov pauv ntawm cov ntaub ntawv caj ces, nws khaws cia thiab kev tsim tawm tsis tuaj yeem. Dawb nucleotides yog cov khoom tseem ceeb koom nrog hauv kev taw qhia thiab lub zog ua haujlwm uas txhawb kev ua haujlwm ntawm cov hlwb thiab lub cev tag nrho.
