Cell motility is a fascinating example of cell behavior that is fundamentally
important to a number of biological and pathological processes. Motility of
eukaryotic cells is based on a complex, self-organized, mechano-chemical machine
consisting of cytoskeletal filaments and molecular motors. This network
is highly dynamic, but able to show precise spatial and temporal organization.
The machine is regulated by a complex network of biochemical reactions
coupled to force and movement-generating processes.
In general, the cytoskeleton is responsible for the movement of the entire
cell and for movements within the cell. There are (roughly) two ways by which
cells can move: swimming (i.e., movement through liquid) and crawling (i.e.,
movement across a rigid surface). Swimming cells experience viscous forces
that are orders of magnitude greater than inertial forces. Some cells move by
undergoing a non-symmetric (i.e., non-reciprocal) sequence of shape changes.
Others use the whipping of flagella or the coordinated beating of cilia to propel
themselves through the surrounding liquid.