Cytoskeleton | home
An outline
The Cytoskeleton
Network of fibers extending throughout the cell 
Cytoskeleton FunctionPlays a major role in organizing the structures and activities of the cell Gives mechanical support to the cell and maintains its shape Especially important in animal cells because no cell wall Regulate biochemical activities of cell Transmit forces across membranes Cell mobility Cell mobilityTypes of mobility Changes in cell location More limited movements of parts of cell Involves interaction of cytoskeleton with proteins called motor molecules Examples Wiggle cilia and flagella Muscles contract Vesicles travel to their destinations Vacuole formation during phagocytosis Three main types of fibersMicrotubules Microfilaments Intermediate filaments 
Cytoskeleton Molecules
Found in cytoplasm of all eukaryotic cell Straight hollow tubes 25 nm in diameter and 200nm - 25um in length Wall composed of globulin molecules called tubulin Each tubulin molecule consists of two similar polypeptide subunits Alpha-tubulin and Beta-tubulin Polar structure Two General GroupsAxonemal microtubules Highly organized and structurally stable Associated with subcellular structures associated with cellular movement Cilia, flagella Cytoplasmic microtubules More loosely organized Cytoplasmic network of microtubules FunctionCell mobility Organization and maintenance of cell shape Serve as tracks for organelles with motor molecules to move Chromosome movements during cell divisionCommon ultrastructureDifferent in length, number per cell, and beating patterns Are an extension of plasma membrane with a core of microtubules 9 + 2 pattern of microtubules Core is made of nine doublets of microtubules arranged in a ring with two single microtubules in the center Microfilaments (Actin Filaments)Long solid filaments about 7 nm long Made of actin, a globular protein, G-actin G-actin linked into long chains Two actin chains are wound into a helix Microfilaments FunctionMaintain cellular shape Muscle contraction Ameboid movement Cell locomotion Cytoplasmic streaming Muscle contractionActin filaments lie parallel to myosin filaments Myosin acts as a motor molecule Walk the two molecules together Localize contraction of cellAmeboid movement Cytoplasmic streaming Intermediate FilamentsNamed for their size Intermediate in size 8-12 nm in diameter Most stable and least soluble cytoskeleton constituent Differ in composition from tissue to tissue Six classes Used as a diagnostic tool for cancer FunctionFunction as the framework or scaffold for the cytoskeleton Specialized for bearing tension Reinforces cell shape Probably fixes organelle position Compose the nuclear lamina