2009-05-20
15:45 at HCI G 7

Active Processes in Living Matter

Frank Jülicher

Max-Planck-Institute for the Physics of Complex Systems, Dresden

Biological cells and tissues represent an extraordinarily complex form of soft matter. This matter is inherently dynamic and far from a thermodynamic equilibrium. A prototype system for the study of dynamics and active processes in cells is the cytoskeleton, a complex gel-like filament network which governs the material properties of cells. Dynamic phenomena in cells such as cell division and cell locomotion are driven by active processes on the molecular scale in the cytoskeleton, for example the action of motor molecules. On the cellular scale, this activity can result in emergent collective modes and spontaneous movements and flows. Furthermore, active processes generate novel material properties in fluids and gels such as contractile stresses and active responses that do not obey a fluctuation dissipation relation. Active processes also play a role in the organization of cells in tissues which exhibit properties of active fluids. In two-dimensional sheets of cells, called epithelia, cell division and cell death drive local rearrangements of cells which determine the geometry of cell packings as well as the size and shape of growing tissues.