Models of self-replication

A protocell could be schematically described as a self-organized, spatially confined collection of chemical species and chemical reactions, able to support the three main properties of living systems: metabolism, reproduction and inheritance. In living systems, while some chemicals are exclusively dedicated to a single activity, like DNA that is devoted to template-based replication, it often happens that the same chemical substance can participate (as substrate, product or catalyst) to many different reactions, which in turn can contribute to the different properties mentioned above; moreover the same reaction may be involved in more than one property. The components are not freely fluctuating within the environment, but are spatially confined by membranes in very small containers (cells).