Proteins yog ib qho ntawm cov organic tseem ceeb ntawm txhua lub cell ntawm lub cev. Lawv ua ntau yam haujlwm: txhawb nqa, taw qhia, enzymatic, thauj, qauv, receptor, thiab lwm yam. Cov txheej txheem thawj, theem nrab, tertiary thiab quaternary ntawm cov protein tau dhau los ua qhov tseem ceeb hloov pauv hloov pauv. Cov molecules no yog dab tsi? Vim li cas qhov tseeb ntawm cov proteins hauv cov hlwb ntawm lub cev tseem ceeb?
YCov khoom tsim ntawm cov proteins
Cov monomers ntawm txhua cov saw hlau polypeptide yog cov amino acids (AA). Cov tsis tshua muaj molecular hnyav cov organic tebchaw no muaj ntau heev nyob rau hauv cov xwm thiab muaj peev xwm nyob ua ib tug ywj siab molecules uas ua lawv tus kheej functions. Ntawm lawv yog cov thauj khoom, txais tos, inhibition lossis ua kom cov enzymes.
Muaj kwv yees li 200 biogenic amino acids nyob rau hauv tag nrho, tab sis tsuas yog 20 ntawm lawv tuaj yeem yog protein monomers. Lawv yaj yooj yim hauv dej, muaj cov qauv crystalline, thiab ntau saj qab zib.
C tshuajLos ntawm qhov pom ntawm AA, cov no yog cov molecules uas yuav tsum muaj ob pawg ua haujlwm: -COOH thiab -NH2. Nrog kev pab los ntawm cov pab pawg no, amino acids tsim chains, sib txuas nrog ib leeg nrog peptide daim ntawv cog lus.
Txhua ntawm 20 proteinogenic amino acids muaj nws tus kheej radical, nyob ntawm seb cov tshuaj lom neeg sib txawv. Raws li qhov muaj pes tsawg leeg ntawm xws li radicals, tag nrho AAs raug faib ua ob peb pawg.
- Nonpolar: isoleucine, glycine, leucine, valine, proline, alanine.
- Polar thiab uncharged: threonine, methionine, cysteine, serine, glutamine, asparagine.
- Aromatic: tyrosine, phenylalanine, tryptophan.
- Polar thiab tsis zoo them: glutamate, aspartate.
- Polar thiab zoo them: arginine, histidine, lysine.
Txhua theem ntawm lub koom haum ntawm cov qauv protein (thawj, theem nrab, theem nrab, quaternary) yog raws li cov saw hlau polypeptide uas muaj AA. Qhov sib txawv tsuas yog yuav ua li cas cov kab ke no tau muab ntim rau hauv qhov chaw thiab nrog kev pab cuam ntawm cov tshuaj lom neeg cov kev sib raug zoo li cas.
Protein thawj qauv
Txhua yam protein yog tsim los ntawm ribosomes - non-membrane cell organelles uas koom nrog hauv kev sib txuas ntawm cov saw hlau polypeptide. Ntawm no, cov amino acids txuas rau ib leeg siv lub zog peptide daim ntawv cog lus, tsim cov qauv tseem ceeb. Txawm li cas los xij, cov qauv tseem ceeb ntawm cov protein no txawv ntawm qhov quaternary, yog li kev loj hlob ntxiv ntawm cov molecule yog tsim nyog.
Proteins nyiamelastin, histones, glutathione, twb nrog cov qauv yooj yim, muaj peev xwm ua tau lawv lub luag haujlwm hauv lub cev. Rau feem coob ntawm cov proteins, cov kauj ruam tom ntej yog tsim kom muaj kev sib koom ua ke ntau dua.
Cov qauv protein thib ob
Kev tsim ntawm peptide bonds yog thawj kauj ruam hauv kev loj hlob ntawm cov protein ntau. Txhawm rau kom lawv ua lawv txoj haujlwm, lawv cov kev sib haum xeeb hauv zos yuav tsum tau hloov qee yam. Qhov no ua tiav nrog kev pab los ntawm hydrogen bonds - tsis yooj yim, tab sis tib lub sij hawm ntau kev sib txuas ntawm cov chaw nruab nrab thiab cov kua qaub ntawm cov amino acid molecules.
Qhov no yog li cas cov txheej txheem thib ob ntawm cov protein tau tsim, uas txawv ntawm quaternary hauv nws txoj kev yooj yim ntawm kev sib dhos thiab hauv zos conformation. Qhov kawg txhais tau hais tias tsis yog tag nrho cov saw hlau raug hloov pauv. Hydrogen bonds tuaj yeem tsim ntawm ntau qhov chaw ntawm qhov sib txawv ntawm ib leeg, thiab lawv cov duab kuj nyob ntawm hom amino acids thiab txoj kev sib dhos.
Lysozyme thiab pepsin yog cov neeg sawv cev ntawm cov proteins uas muaj cov qauv thib ob. Pepsin koom nrog hauv kev zom zaub mov, thiab lysozyme ua haujlwm tiv thaiv hauv lub cev, rhuav tshem cov phab ntsa ntawm tes ntawm cov kab mob.
Txoj kev ntawm cov qauv thib ob
Kev sib haum xeeb hauv zos ntawm peptide saw tuaj yeem sib txawv ntawm ib leeg. Ob peb lub kaum ob twb tau kawm, thiab peb ntawm lawv yog cov feem ntau. Ntawm lawv yog alpha helix, beta txheej thiab beta twist.
Alpha kauv –ib qho ntawm feem ntau conformations ntawm cov qauv thib ob ntawm cov protein ntau. Nws yog ib lub pas nrig thav duab nrog stroke ntawm 0.54 nm. Amino acid radicals taw tes sab nraud
Tab tes xis yog feem ntau, thiab sab laug tes tuaj yeem pom qee zaum. Lub shaping muaj nuj nqi yog ua los ntawm hydrogen bonds, uas stabilize lub curls. Cov saw hlau uas tsim cov alpha helix muaj tsawg heev proline thiab polar charged amino acids.
- Lub beta tig yog cais rau hauv kev sib cais, txawm hais tias nws tuaj yeem hu ua ib feem ntawm beta txheej. Cov kab hauv qab yog qhov khoov ntawm cov saw peptide, uas yog txhawb nqa los ntawm hydrogen bonds. Feem ntau qhov chaw ntawm qhov khoov nws tus kheej muaj 4-5 amino acids, ntawm cov uas muaj proline yog yuav tsum tau. Lub AK no tsuas yog ib lub cev tawv thiab luv luv, uas tso cai rau nws los ua tus kheej tig.
- Cov beta txheej yog cov saw hlau ntawm cov amino acids uas tsim ob peb khoov thiab stabilizes lawv nrog hydrogen bonds. Qhov no conformation yog heev zoo ib yam li ib daim ntawv ntawm folded rau hauv ib tug accordion. Feem ntau, aggressive proteins muaj qhov zoo li no, tab sis muaj ntau qhov kev zam.
Txhim qhov sib txawv ntawm qhov sib npaug thiab antiparallel beta-txheej. Hauv thawj kis, C- thiab N- xaus ntawm qhov khoov thiab qhov kawg ntawm cov saw hlau sib koom, thiab hauv qhov thib ob lawv tsis ua.
Tertiary structure
Kev ntim cov protein ntxiv ua rau tsim cov qauv tertiary. Qhov kev sib haum xeeb no ruaj khov nrog kev pab ntawm hydrogen, disulfide, hydrophobic thiab ionic bonds. Lawv cov lej loj tso cai rau twisting tus qauv thib ob rau hauv ib qho nyuaj dua.tsim thiab stabilize nws.
cais globular thiab fibrillar proteins. Lub molecule ntawm globular peptides yog ib tug kheej kheej qauv. Piv txwv li: albumin, globulin, histones hauv tertiary qauv.
Fibrillar proteins tsim cov strands muaj zog, qhov ntev ntawm qhov ntev tshaj lawv qhov dav. Xws li cov proteins feem ntau ua cov txheej txheem thiab kev ua haujlwm. Piv txwv li yog fibroin, keratin, collagen, elastin.
Cov qauv ntawm cov protein hauv cov qauv quaternary ntawm cov molecule
Yog tias ob peb lub globules ua ke rau hauv ib qho nyuaj, lub npe hu ua quaternary yog tsim. Qhov kev sib haum xeeb no tsis zoo rau txhua tus peptides, thiab nws tau tsim thaum nws tsim nyog los ua cov haujlwm tseem ceeb thiab tshwj xeeb.
Txhua lub globule nyob rau hauv cov protein complex yog ib tug cais sau los yog protomer. Ua ke, cov qauv ntawm cov proteins ntawm cov qauv quaternary ntawm ib lub molecule hu ua oligomer.
Feem ntau, xws li cov protein muaj ntau qhov kev ruaj khov uas hloov pauv txhua lub sijhawm, nyob ntawm qhov cuam tshuam ntawm lwm yam, lossis thaum tsim nyog los ua haujlwm sib txawv.
Qhov sib txawv tseem ceeb ntawm tertiary thiab quaternary qauv ntawm cov protein yog cov ntawv cog lus sib txuas, uas yog lub luag haujlwm rau txuas ntau lub globules. Nyob rau hauv nruab nrab ntawm tag nrho cov molecule, feem ntau muaj ib tug hlau ion, uas ncaj qha cuam tshuam rau kev tsim ntawm intermolecular bonds.
Ntxiv cov qauv protein
Tsis yog ib qho saw ntawm amino acids txaus los ua haujlwm ntawm cov protein. ATFeem ntau, lwm yam khoom ntawm cov organic thiab inorganic xwm yog txuas nrog xws li molecules. Txij li cov yam ntxwv no yog tus yam ntxwv ntawm cov enzymes ntau dhau, muaj pes tsawg leeg ntawm cov proteins nyuaj feem ntau muab faib ua peb ntu:
- Apoenzyme yog cov protein ib feem ntawm cov molecule, uas yog cov amino acid sequence.
- Coenzyme tsis yog protein, tab sis yog ib feem ntawm cov organic. Nws tuaj yeem suav nrog ntau hom lipids, carbohydrates, lossis txawm tias nucleic acids. Qhov no suav nrog cov neeg sawv cev ntawm cov tshuaj lom neeg lom neeg, cov uas muaj cov vitamins.
- Cofactor - ib feem ntawm cov organic, sawv cev rau feem coob ntawm cov neeg mob los ntawm cov hlau ions.
Cov qauv ntawm cov proteins nyob rau hauv lub quaternary qauv ntawm ib lub molecule yuav tsum muaj kev koom tes ntawm ob peb molecules ntawm txawv keeb kwm, li ntawd, ntau enzymes muaj peb yam ib zaug. Ib qho piv txwv yog phosphokinase, ib qho enzyme uas ua kom muaj kev hloov pauv ntawm pawg phosphate los ntawm ATP molecule.
Tus qauv quaternary ntawm cov protein molecule tsim nyob qhov twg?
Cov saw hlau polypeptide pib ua ke ntawm ribosomes ntawm tes, tab sis ntxiv kev loj hlob ntawm cov protein tshwm sim hauv lwm cov organelles. Cov molecule uas tsim los tshiab yuav tsum nkag mus rau hauv lub cev thauj mus los, uas muaj xws li lub nuclear membrane, ER, Golgi apparatus thiab lysosomes.
Qhov teeb meem ntawm cov qauv spatial ntawm cov protein tshwm sim nyob rau hauv endoplasmic reticulum, qhov twg tsis yog tsuas yog ntau hom kev sib cog lus tsim (hydrogen, disulfide, hydrophobic, intermolecular, ionic), tab sis kuj ntxiv coenzyme thiab cofactor. Qhov no tsim ib quaternaryprotein qauv.
Thaum cov molecule npaj txhij rau kev ua haujlwm, nws nkag mus rau hauv cytoplasm ntawm lub xovtooj ntawm tes lossis Golgi apparatus. Nyob rau hauv rooj plaub tom kawg, cov peptides tau ntim rau hauv lysosomes thiab thauj mus rau lwm qhov chaw ntawm lub cell.
Piv txwv ntawm oligomeric proteins
Quaternary qauv yog cov qauv ntawm cov proteins, uas yog tsim los pab txhawb kev ua haujlwm ntawm lub luag haujlwm tseem ceeb hauv lub cev muaj sia. Kev sib haum xeeb ntawm cov organic molecules tso cai, ua ntej ntawm tag nrho cov, los cuam tshuam kev ua hauj lwm ntawm ntau yam metabolic dab (enzymes).
Cov proteins uas tseem ceeb hauv kev noj qab haus huv yog hemoglobin, chlorophyll thiab hemocyanin. Lub nplhaib porphyrin yog lub hauv paus ntawm cov molecules, nyob rau hauv nruab nrab ntawm uas yog ib tug hlau ion.
Hmoglobin
Cov qauv quaternary ntawm hemoglobin protein molecule muaj 4 globules txuas nrog cov ntawv cog lus sib txuas. Hauv nruab nrab yog porphin nrog ferrous ion. Cov protein yog thauj mus rau hauv cytoplasm ntawm erythrocytes, qhov chaw lawv nyob li ntawm 80% ntawm tag nrho cov ntim ntawm cytoplasm.
Lub hauv paus ntawm cov molecule yog heme, uas muaj ntau inorganic xwm thiab yog xim liab. Nws tseem yog thawj cov khoom tawg ntawm hemoglobin hauv daim siab.
Peb txhua tus paub tias hemoglobin ua lub luag haujlwm tseem ceeb hauv kev thauj mus los - hloov cov pa oxygen thiab carbon dioxide thoob plaws hauv tib neeg lub cev. Txoj kev sib haum xeeb ntawm cov protein molecule tsim cov chaw tshwj xeeb, uas muaj peev xwm los khi cov roj sib txuas rau hemoglobin.
Thaum cov protein-gas complex tsim, thiaj li hu ua oxyhemoglobin thiab carbohemoglobin tsim. Txawm li cas los xij, muaj ib qho ntxivntau yam kev sib koom ua ke, uas yog qhov ruaj khov heev: carboxyhemoglobin. Nws yog ib qho nyuaj ntawm cov protein thiab cov pa roj carbon monoxide, qhov ruaj khov uas piav qhia txog kev tawm tsam ntawm kev ua tsis taus pa nrog cov tshuaj lom ntau dhau.
YChlorophyll
Lwm tus neeg sawv cev ntawm cov proteins nrog cov qauv quaternary, uas nws daim ntawv cog lus twb tau txais kev txhawb nqa los ntawm magnesium ion. Lub luag haujlwm tseem ceeb ntawm tag nrho cov molecule yog kev koom tes hauv cov txheej txheem ntawm photosynthesis hauv cov nroj tsuag.
Muaj ntau hom chlorophylls, uas sib txawv ntawm ib leeg hauv cov radicals ntawm lub nplhaib porphyrin. Txhua yam ntawm no yog cim nrog ib tsab ntawv cais ntawm cov tsiaj ntawv Latin. Piv txwv li, cov nroj tsuag hauv av yog tus cwj pwm los ntawm qhov muaj chlorophyll a lossis chlorophyll b, thaum algae kuj muaj lwm hom protein no.
Hemocyanin
Cov molecule no yog ib qho analogue ntawm hemoglobin hauv ntau cov tsiaj qis (arthropods, molluscs, thiab lwm yam). Qhov sib txawv tseem ceeb hauv cov qauv ntawm cov protein nrog cov qauv quaternary molecular yog qhov muaj zinc ion tsis yog hlau ion. Hemocyanin muaj xim xiav.
Qee zaum tib neeg xav tias yuav ua li cas yog tias peb hloov tib neeg hemoglobin nrog hemocyanin. Nyob rau hauv cov ntaub ntawv no, ib txwm cov ntsiab lus ntawm cov tshuaj nyob rau hauv cov ntshav, thiab tshwj xeeb amino acids, yog cuam tshuam. Hemocyanin kuj tsis ruaj khov los tsim ib qho nyuaj nrog cov pa roj carbon dioxide, yog li "cov ntshav xiav" yuav muaj qhov ua rau cov ntshav txhaws.
