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BIOL 1090 Final Review Notes

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BIOL 1090
Dan Meegan

BIOL 1090 Final Review Notes PreMidterm Material Cytoskeleton Lecture Pre12Dynamic network of protein filaments that forms the cellular scaffolding as well as transport system for organelles and vesiclesFunctions o Structural support o Intracellular transport o Contractility and motility o Spatial organization within a cellMajor elements o Microtubules hollow unbranched tubules of tubulin o Intermediate filaments fibrous various proteins o Microfilaments solid thin branched actin polymers MicrotubulesLargest cytoskeletal element 25 nm diameterPolymer of proteins alpha and betatubulinAlphabeta heterodimers form long protofilaments13 protofilaments form longitudinal array hollow cylinderHeterodimers aligned in the same directionhead to tailStructural Polarity o Fast growingend top of figure o Slow growingend bottom of figureStructural polarity is important for growthshrinkage and direction of movement of material along MT Associated Motor ProteinsDynein minus end directed and kinesin plus end directed can power intracellular transportUse ATP to generate forceCan move material along MT tractCan generate sliding force between MTs Dynamic Assembly and disassemblyIn vivo leads to rapid turnover of most Mts within cell halflife is minutes o Dynamic InstabilityCatastrophe Shrinkage can occur very rapidly at the plus end o Can be growing on one side and disassembling on the other so it is moving but stationaryFormation of MTs is regulatedcontrolled Microtubule Associated Proteins MAPsMicrotubuleorganizing center MTOC is the central site of MT assemblyCentrosome if a major site of microtubule organization for in animal cellsIntermediate FilamentsIntermediate size 1012 nm diameterExclusive to multicellular animalsProvide structural support and mechanical strengthStable relative to MTs or microfilamentsFibrous proteins contain central alphahelical domain5 classes StructureAlphahelical domains wrap around each other forming ropelike dimer coiledcoilMonomers are aligned in parallel if dimers are polar molecules with different N and C termini step 2Dimers associate antiparallel assembled filaments are not polar step 3MicrofilamentsSmallest cytoskeletal elementapprox 8 nmPolymer of the actin proteinPolypeptide 42 kDa binds ATP o Individuals are Gactin globular o Polymerized filament FactinFunctions o Maintenance of cell shape o Cell movement o Cytokinesis o Muscle contraction Filamentous FactinGactin monomers have polar structureMonomers are incorporates into the filament in the same orientationFactin filament is polar Assembly o Gactin polymerizes reversibly o Nucleation slow Gactindimerstrimmersshort filaments o Elongation fast monomers add to both ends faster atendPolymerization depolymerisation ad structureorganization of Factin filaments are regulated by actinbuilding proteinsMyosinFactin associated motor proteinLarge family of proteinsMost move towardend of microfilament
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