Download - Citoskelet
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UNIVERZITET U TUZLIPRIRODNO-MATEMATIČKI FAKULTET
ODSJEK:BIOLOGIJAPREDMET:BIOLOGIJA ĆELIJE
CITOSKELET
Student: Čamdžić Zerina
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• Citoskelet (grč.kytos+skeleton=kostur),to je složena mreža vlakana izgrađena od preko 20 vrsta citoplazmatičnih proteina.
• Proteini omogućavaju promjenu oblika ćelije,kretanje organela unutar ćelije i povezivanje ćelija.
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• Pomoću citoskeleta mišićna vlakna se kontrahuju,crvena krvna zrnca zadržavaju bikonkavan izgled a ćelije epitela crijeva formiraju mirkovile.
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Elementi citoskeleta-Plazma membrana,endoplazmatskiretikulum,ribosomi,mikrofilamenti,mikrotubule i mitohondrije.
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Funkcije citoskeleta
-dioba ćelije-kretanje hromosoma -vezivanje mRNA- izgradnja diobenog vretena-trodimenzionalna mreža-prožima citoplazmu ćelije-povezuje jedro i organele-određuje oblik ćelije-daje potporu ćeliji
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• Kod eukariota citoskelet izgrađuju 3 osnovna tipa proteinskih niti.
• Tu spadaju: -mikrofilamenti -mikrotubuli -intermedijarni mikrofilamenti.
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Mikrofilamenti
• Aktinski mikrofilamenti nastaju spontanom polimerizacijom proteina aktina u uvjetima povišene koncentracije Ca++ i Mg++
• Nastane tanka i dugačka spiralno savijena nit
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Mikrofilamenti-uloga
• Tvore stanični potporanj-citoskelet,koji istovremeno služi za pokretanje
• U kombinaciji s proteinom miozinom omogućava kontrakcije mišićnih stanica.
• Stvaraju diobeno vreteno• Ameboidno kretanje• Strujanje tvari kroz citoplazmu
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Mikrotubuli
• Nastaju polimerizacijomproteina tubulina(alfa i beta),te nastanu niti protofilamenatakoje se namatanjemformiraju u šupljecilindre.
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Mikrotubuli-uloga
• Tvore citoskelet i daju oblik i čvrstoću stanici• Po njima se ostale organele kreću kroz
citoplazmu• Glavni su element bičeva i trepetljiki• Tvore diobeno vreteno dok se stanica dijeli
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• Osim kretanja nastalog usljed dinamičke nestabilnosti samih mikrotubula,vlakna mikrotubula su i supstrati duž kojih se molekuli proteina mogu kretati.
• Glavni motorni proteini mikrotubula su kinezin,koji se kreće ka (+) kraju mikrotubule i dinein,koji se kreće ka (-) kraju mikrotubule.
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Intermadijarni filamenti
• Intermedijarni filamenti (IF) su elementi citoskeleta koji su najmanje izučeni. Njihovo prisustvo kod većine eukariotskih ćelija i organizama je dokazano,ali postoje kontroverze kod gljiva i nižih eukariota.Njihovo prisustvo u ćelijama je tkivno zavisno i nejednako.
• Kada se pogleda njihova zastupljenost po tkivima uočava se da su koncentrisani u ćelijama koje se odupiru mehaničkim pritiscima i deformacijama.
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• Postoji nekoliko tipova IF:-keratinski filamenti (epitelne ćelije)-dezminski filamenti (mišićno tkivo)-neurofilamenti (nervno tkvio)-viementinski (mehanička snaga mišića)-glijalni filamenti
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