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Cell bio - final.doc

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Molecular and Cellular Biology
MCB 2050

Cell biofinalFunctions of the NucleusStorage replication and repair of genetic materialExpression of genetic materialoTranscription oSplicingRibosome biosynthesisStructure of the NucleusNuclear envelopeoNuclear membraneoNuclear poresoNuclear laminaNuclear contentsoChromatinoNucleoplasmoNucleolusoNuclear matrixNuclear envelopeStructure fig 122A2 parallel phospholipid bilayers separated by 1050 nmOuter membrane binds ribosomes and is continuous with rough endoplasmic reticulumInner membrane bears integral proteins which connect to nuclear laminaFunctions of Nuclear EnvelopeSeparates nuclear content from cytoplasm separating transcription and translationSelective barrier allowing limited movement of molecules between nucleus and cytoplasmBinds nuclear laminaNuclear LaminaThin meshworkoLamins type 5 IF is approximately 10nm is diameter and it integrity is regulated by phosphorylationBound of the inner surface of the NE via prenyl group at Cterminal cysteine and lamin polypeptideSupport structure for NEAttachment site for chromatinNuclear PoresGateways between cytoplasm and nucleoplasm 3000 to 4000 pores per nucleusMembranes fuse to form pores approximately 120nm in diameterPores contain a complex protein structure called the Nuclear Pore Complex NPCNuclear Pore ComplexAbout 200 polypeptides called nucleoporins NUPso2530 different NUPs in multiple copiesAn 8 fold repeat forming the structure called octagonal symmetryFits into the poreProjects into the cytoplasm and nucleoplasmFunctional diameter 9nmDoughnut like cytoplasmic view basket like nuclear view5Huge 125 x 10 kDa supramolecular complexFunctions of the Nuclear Pore ComplexPassive diffusion of molecules smaller than 50kDa or 9nmo100minpore histones nucleotidesRegulated movement of larger moleculesoNuclear proteins move inoRNA ribosomal subunits cytoplasmic proteins move outo6minporeNuclear function dependent upon protein importStructural proteinsoNuclear lamins and matrixoDNA packaging histonesDNA replicationDNA repairTranscriptionRNA processing and exportRibosome synthesis and exportFactors needed for nuclear importNuclear localization signal NLSoStretch of positively charged amino acids near Cterminus of proteinKaryopherins
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