ReactionDiffusion Systems in Intracellular Molecular Transport and Control

Chemical reactions make cells work only if the participating chemicals are delivered to desired locations in a timely and precise fashion. Most research to date has focused on activetransport mechanisms, although passive diffusion is often equally rapid and energetically less costly. Capitalizing on these advantages, cells have developed sophisticated reactiondiffusion RD systems that control a wide range of cellular functions—from chemotaxis and cell division, through signaling cascades and oscillations, to cell motility. These apparently diverse systems share many common features and are “wired” according to “generic” motifs such as nonlinear kinetics, autocatalysis, and feedback loops. Understanding the operation of these complex biochemical systems requires the analysis of pertinent transportkinetic equations or, at least on a qualitative level, of the characteristic times of the constituent subprocesses. Therefore, in reviewing the manifestations of cellular RD, we also describe basic theory of reactiondiffusion phenomena.