Spontaneous overcrowding in liposomes as possible origin of metabolism.

We emphasize here that, in considering the initial prebiotic reactions, it is fundamental to take into consideration the critical threshold concentration, in particular when talking about self-replication and initial metabolism. It is also shown that the in situ formation of vesicles in a solution containing macromolecular solutes, permits to obtain filled vesicles which are overcrowded of those solutes and therefore viable for complex biochemical reactions.