Evolutionary Origin of Life Scenarios: Paradox of Plasma Membrane

The structural and functional properties of the cell surface (plasma) membrane (a.k.a. plasmalemma) relevant to evolutionary paradigms for biogenesis are reviewed. Such a partition would have been essential for the transition from abiotic chemistry to biochemistry, the physicochemical organization of the protocytosol, and the subsequent evolutionary differentiation of first life forms. However, an incremental evolutionary origin for the plasmalemma is gainsaid by these very requirements. The most plausible type of first membrane, a purely lipid bilayer, would have provided the necessary containment principle, but because of its demonstrable impermeability to requisite inorganic and organic molecules, the same membrane would have simultaneously precluded further development, even maintenance, of the emerging protocells. As an alternative primordial membrane model, protein microsieves are addressed and found wanting to the concentrative requirements of biologically relevant synthetic chemistry and its organization. Existing plasma membranes are composites of lipids and proteins, where certain of the proteins function as permeation channels and transport catalysts ( carriers or permeases ). However,. the prospect of a selectively permeable lipoprotein membrane assembling de novo by purely natural processes is contraindicated not only by the egregious improbabilities but also by a number of definable physicochemical constraints. Meanwhile, to a creationist model of cell (ergo life\u27s) origin, the integrated structural and functional complexity of extant plasma membranes provides yet further evidence of purposeful design. Not the least of this evidence would be the determinative informational principles on which membrane permeabilities are based