Energetically plausible model of a self-maintaining protocellular system

Most of the models for cellular origin stress one of these two approaches: "replication-first" or "metabolism-first." The model presented here focuses on the latter, consisting of the combination of kinetic and energetic descriptions of protocellular metabolism. In this model, the membrane plays a very crucial role in the maintenance of the cell and the osmotic stability. The model contains the following elements: structural membrane elements (Lm), transducers (T), molecules (E) that combine enzyme-like activity with the transport of elements through the membrane, energy-rich molecules (A), precursors of each type of molecule (l, t, e, and a, respectively), and an impermeable substance (x). Different kinetic parameters lead to a wide region of stable steady states, as studied through numerical analysis. The system presents stability under different external conditions. Two energy source regimes have been studied: periodic and nonperiodic. The kinetic restrictions that lead to osmotic stability are also addressed in this paper.