Abstract
The actin-myosin cytoskeleton plays an essential role in the motility of a cell crawling on a solid substrate. A good level of description is the theory of active gels, which was the subject of the 2019 lecture and which we have constructed to study the cytoskeleton precisely. The theory respects the conservation of momentum but not of energy, due to the energy consumption of active proteins in the cell. The cytoskeleton is made up of polar actin filaments interacting with myosin molecular motors, and cell movement requires global polarization in the direction of motion. Polymerization and depolymerization of actin filaments also play a fundamental role in motility.
Following a brief presentation of the properties of polar active gel theory as applied to the cytoskeleton, this lecture and the next proposed simple applications of the theory related to cell motility. The first application is a very naive model of the motility of a cell fragment confined between two solid surfaces, which clearly shows the relative roles of polymerization and depolymerization and cytoskeletal contractility.
