The physics of cell motility.

Cell locomotion begins with a protrusion from the leading periphery of the cell. What drives this extension? Here we present a model for the extension of cell protuberances that unifies certain aspects of this phenomenon, and is based on the hypothesis that osmotic pressure drives cell extensions. This pressure arises from membrane-associated reactions, which liberate osmotically active particles, and from the swelling of the actin network that underlies the membrane.