Lect. 04 F10 - Introduction to the Cytoskeleton and Polymer...

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1 1998 Nikon Small World Competition Winner: Jakob Zbaeren, endothelial cells Introduction to the Cytoskeleton and Polymer Dynamics Cells behave in a dynamic, mechanically integrated manner Cells can change shape Cells display internal organization Cells can transport molecules throughout the cytoplasm Cells exhibit various forms of mobility These behaviors are mediated by the cytoskeleton
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2 Studies with the electron microscope revealed that arrays of protein filaments coursed through the cytoplasm 1) Microtubules 25 nm diameter, hollow in cross-section 2) Intermediate filaments 10 nm in diameter 3) Microfilaments 5-8 nm in diameter Three sizes classes: The three classes of cytoskeletal filaments Intermediate Filaments Microtubules Microfilaments IFs extend throughout the cytoplasm and form a lamina beneath the nuclear membrane. Microtubules emanate from the centrosome, which is often located near the nucleus. Microfilaments tend to be organized into networks associated with the cell periphery (cortex).
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3 Microtubule Function 1) Microtubules organize cellular organelles within the cytoplasm 2) Microtubule provide tracks on which to move cell constituents 3) Microtubules provide the force for cilila and flagella beating axonal transport 4) Microtubules form the mitotic spindle Microfilament Function In general, microfilaments function as contractile fibers -can form stable or transient structures 1) Microfilaments push and pull the plasma membrane, resulting in changes in cell shape. 2) Specialized assemblies of microfilaments provide the mechanism to generate force during muscle contraction. microvilli lamellipodium contractile ring
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4 Intermediate Filament Function 1) IFs are components of the nuclear lamina that may help to organize chromatin within the nucleus. Control nuclear disassembly/reassembly during mitosis. 2) IFs are thought to provide mechanical integrity to tissues that are subject to mechanical stress.
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Lect. 04 F10 - Introduction to the Cytoskeleton and Polymer...

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