The lipid world

The continuity of abiotically formed bilayer membranes with similar structu res in contemporary cellular life, and the requirement for microenvironment s in which large and small molecules could be compartmentalized, support th e idea that amphiphilic boundary structures contributed to the emergence of life. As an extension of this notion, we propose here a 'Lipid World' scen ario as an early evolutionary step in the emergence of cellular life on Ear th. This concept combines the potential chemical activities of lipids and o ther amphiphiles, with their capacity to undergo spontaneous self-organizat ion into supramolecular structures such as micelles and bilayers. In partic ular, the documented chemical rate enhancements within lipid assemblies sug gest that energy-dependent synthetic reactions could lead to the growth and increased abundance of certain amphiphilic assemblies. We further propose that selective processes might act on such assemblies, as suggested by our computer simulations of mutual catalysis among amphiphiles. As demonstrated also by other researchers, such mutual catalysis within random molecular a ssemblies could have led to a primordial homeostatic system displaying rudi mentary life-like properties. Taken together, these concepts provide a theo retical framework, and suggest experimental tests for a Lipid World model f or the origin of life.