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Lecture 5

Lecture 5 cont. - Structure and Function of Filaments.doc

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BIO1140 Lecture 5 contFebruary 1 2011Dynamic CharacterMicrofilaments have polarity stacked together one end thehas accessible ATPActin with ATP bound to it is more likely to polymerizeend grows once bound into microfilament ATP is hydrolyzed to ADP more likely to dissociate ADP Gactin dissociates quite readilyend of the filament dissociatesDepending on the rates of 2 processes microfilaments can grow stay the same size or shrinkGives the cell a lot of flexibility in controlling microfilament formation and shape of microfilament slow part is getting first few monomers together called nucleation variety of proteins within the cell that help nucleationThere can be nucleating proteins that organize initial monomers and speed up polymerization of microfilaments proteins that mind to actin monomers and prevent them from binding to the microfilamentthey slow formation proteins that facilitate the formation of microfilaments proteins that break down microfilamentsdepolymerisation capping proteins will slow down the growth of microfilaments by blocking the microfilament from growing proteins that can bind microfilaments together in different ways all called actin binding proteinsActin proteins are responsive to cell signalling pathways the cell is able to control growth and placement of microfilament for particular purpose requiresDrugs that are useful in microfilaments cytochalisinprevents actin from polymerizing new microfilaments cannot form old ones cannot grow microfilaments tend to disassociate phalloidinstables microfilaments neither grow nor shrink any process relying on dynamic nature of microfilaments is inhibitedFunctions of MicrofilamentsShape and support of the cell particulary animal cellsMotility movement within the cell movement of entire cell movement of part of the cellShape and support variety of different ways that microfilaments give cells shape and support true in animal cells because they lack a cell wall important in supporting the cell membrane in animal cells network of filaments called the cell cortex lies beneath the cell membrane connected to the cell membrane by peripheral membrane proteins bundles of microfilaments in some places exmicrovillismall cell extensions elaboration of cell membrane involved in transport they can be found in places where transport is important narrow diameter numerous
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