Figure 1.

Schematic of one conception of a hypothetical protocell. A chemical reaction network within a lipid vesicle acquires nutrients that lead to the copying of nucleic acids and the synthesis of peptides and lipids. Here, the internal chemistry of the protocell supports membrane growth by synthesizing lipid. Membrane growth then leads to the division of unstable intermediate structures through environmental shear forces. Reactive monomeric building blocks and reaction by-products, i.e. waste, passively diffuse across the membrane. Ideally, an internal protometabolic network would sustain the protocell across many generations.