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"Animation of the inside of a typical human cell, showing the components of its supportive cytoskeleton. The main supportive structures are thin microfilaments made of the protein actin (white), and larger microtubules, made from the protein tubulin (blue-green blobs). Microtubules are important in maintaining the cell's shape, helping its movement and motility, and providing a framework through which components can be moved around the cell. One way this occurs is through the motor protein kinesin (red). A microtubule grows to where a cellular component is required. The kinesin binds to a transport vesicle containing the component protein, and the head end of the kinesin binds to the microtubule. It then 'walks' along the microtubule, from the centre to the edge of the cell, carrying the vesicle's content to where it is required. The growth of the microtubules is controlled by the centrosome, a central body in the cell. This contains two centrioles (orange) made of tubulin, surrounded by a protein body. This clip is available with components labelled. See K005/0830."