Primordial membranes: more than simple container boundaries

Cellular membranes, which are self-assembled bilayer structures mainly composed of lipids, proteins and conjugated polysaccharides, are the defining feature of cell physiology. It is likely that the complexity of contemporary cells was preceded by simpler chemical systems or protocells during the various evolutionary stages that led from inanimate to living matter. It is also likely that primitive membranes played a similar role in protocell 'physiology'. The composition of such ancestral membranes has been proposed as mixtures of single hydrocarbon chain amphiphiles, which are simpler versions of modern lipids. In this review, we discuss the origins, self-assembly patterns, potential functions of these amphiphiles, and their possible roles in protocell activities, as well as their possible evolution towards modern lipids.