Protocells: Chemical Reactions within Active Boundaries

Protocells are rudimentary physico-chemical structures from which highly complex contemporary cells somehow evolved. They constitute a current 'hot topic' of research as they provide a potential bridge between two worlds which are seemingly disconnected: non-living molecules and highly organised living matter. Computational and mathematical models are essential in guiding and interpreting empirical research on protocells.

In this talk, I will present a theoretical model of a protocell, based on a hypothetical lipid vesicle which encapsulates chemical reactions in its water-filled core. Whilst many protocell models treat the lipid membrane of the protocell as a passive structure, simply containing a set of "interesting" solute molecules in close proximity, I will instead argue for a different perspective in which the membrane is modelled as an active and integrated part of the whole protocell system. Under this perspective, the reaction space inside a protocell is not a fixed volume with constant supply of nutrients, but is rather a variable-volume solvent (caused by water osmosis across the semi-permeable membrane) which has a solute diffusion surface dependent on the current membrane size.

In this context, I will show how interesting emergent behaviour can arise in simple chemical reactions encapsulated inside a protocell volume. Along the way, I will explain a new idea called 'osmotic coupling' whereby independent sets of chemical reactions (i.e. having no chemical species in common) that exist inside the same protocell could become indirectly coupled to each other, affecting each others dynamics, simply because they share the same changing volume space. This work makes some inroads into understanding protocells as whole chemical systems, and the talk should be of general interest to anyone working in modelling chemical reactions or the origins of life.