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. Author manuscript; available in PMC: 2012 Aug 15.
Published in final edited form as: Multiscale Model Simul. 2011 Nov 17;9(4):1420–1443. doi: 10.1137/100815335

Figure 1.

Figure 1

(a) Schematic diagram of a crawling cell in top down view (with nucleus and cytoskeleton). (b) Side view of a cell fragment with diameter ≈ 10μm, and thickness ≈ 0.1 – 0.2μm showing membrane (grey) and cytosol (white). Rectangular region from (b) is enlarged in (c) to show the interconversion of two proteins, a the active membrane-bound form and b the inactive cytosolic form. The regulatory system includes (in)activation (with positive feedback, dashed arrow) and diffusion of a, b everywhere inside the cell domain Ωc. (d) In the simulation, we do not distinguish membrane from cytosol in the interior of Ωc, so a, b occupy the same “compartment”, with Db ≫ Da. (e) We model the 2D top-down projection of the cell Ωc, devoid of nucleus and other structures, with elastic boundary representing the cortex, assuming a uniform thickness. The cell moves in the direction of the outward normal forces.