Mechanics-notes - Mechanics and tissues O verview Cells are...

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© M. S. Shell 2009 1/6 last modified 11/30/2009 Mechanics and tissues Overview Cells are not static beings – they must change shape, split in two, and effect movement Communities of cells— tissues —must also exhibit mechanical strength These mechanical properties of cells rely on both intracellular and extracellular networks of protein fibrils , and other components These fibril systems are regulated just like other cellular systems, and are highly dynamic Intracellular mechanics The cytoskeleton in eukaryotic cells consists of three main networks of protein fibrils intermediate filiments microtubules actin filaments Intermediate filaments ~10nm in diameter Toughest and most durable intracellular filaments – enables cells to resist stretching Composed of coiled-coil protein dimers wrapped around each other and bundled together Anchored to nucleus and plasma membrane at cell-cell junctions Provides mechanical strength in the cytoplasm in tissue cells (epithelia) – made of keratins Forms a mesh around the nuclear envelope to strengthen it – the nuclear lamina made from lamins Microtubules ~25 nm in diameter Long, hollow tubes made of the protein tubulin Responsible for
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© M. S. Shell 2009 2/6 last modified 11/30/2009 anchoring organelles guiding intracellular transport ( kinesins and dyneins walk along them, pulling attached organelles) facilitating cell division and chromosome allocation during mitosis basic unit in cilia and flagella Microtubules are formed by the self-assembly of tubulin gG heterodimers dimers self-assemble head to tail to form filaments filaments associate to form tubes (about 13 filaments per tube) dimers can then add to the ends to “grow” a microtubule driven by highly specific and favorable recognition interactions of tubulin proteins with each other Microtubules grow from the centrosome , typically close to the cell nucleus matrix of proteins ± -tubulin nucleation sites to promote formation of microtubules
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Mechanics-notes - Mechanics and tissues O verview Cells are...

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