protocell

Protocell is a term used in origin-of-life research to describe simple, cell-like structures that can maintain an internal environment separated from the outside, harbor basic metabolic reactions, and potentially grow and divide. Protocells are envisioned as precursors to real cells, bridging the gap between purely chemical systems and living organisms. They are not fully living but exhibit some life-like properties that could be subject to natural selection.

Most protocells rely on a boundary such as a lipid bilayer or other amphiphilic membrane to create a defined interior and to enable selective exchange with the surroundings. This compartmentalization concentrates reactants, protects fragile reaction networks, and allows gradients that can drive metabolism or replication.

Model systems studied as protocells include fatty acid or phospholipid vesicles (liposomes) that encapsulate simple catalytic networks, nucleic acids, or ribozymes; coacervates formed from polymers; and proteinoid microspheres. In some experimental setups, vesicles can grow by uptake of precursors and divide upon growth or mechanical perturbation, while internal reactions produce waste or energy that supports further activity.

The protocell concept supports two broad research directions. In origin-of-life studies, it helps explore how a non-replicating chemical system could become a self-sustaining, heritable entity. In synthetic biology, protocell models serve as platforms for constructing minimal cell-like systems with potential applications in medicine and biotechnology.