The cytoskeleton is a three-dimensional network of fibers, composed of filamentous protein, which runs throughout the matrix of living cells, providing a framework for organelles, anchoring the cell membrane, and providing a suitable surface for chemical reactions to take place. The cytoskeleton also provides the cell with motility – the ability of the entire cell to move around and for material to be moved within the cell.
Three main protein systems constitute the cytoskeleton. These are, in order of typical abundance:
Although the term "cytoskeleton" is well used and accepted, it unfortunately gives an impression of a rather static entity. In fact, however, all three constituents are dynamic structures: they constantly change shape through cycles of polymerization / depolymerization and interactions with other proteins. Each type of fiber looks and functions differently.