Four processes were needed for the spontaneous origin of life on Earth: Non-living synthesis of simple organic molecules Assembly of these molecules into polymers Origin of self replicating molecules that made inheritance possible Packaging of these molecules into membranes with an internal chemistry different from their surroundings

Protocells: Combinations of abiotically produced molecules surrounded by a membrane or membrane–like structure.

Exhibit some of the properties associated with life simple reproduction simple metabolism the maintenance of an internal chemical environment different from that of their surroundings.

Protocells could have developed from coacervate droplets: Complex spherical units that spontaneously form when concentrated mixtures of macromolecules are held in the right temperature, ionic composition, and pH Absorb and incorporate various substances from the surrounding solution Laboratory experiments demonstrate that protocells could have formed spontaneously from abiotically produced organic compounds. For example, small membrane–bounded droplets called liposomes can form when lipids or other organic molecules are added to water.

How could a protocell develop? Fatty acids spontaneously form membranes (animation #4, video clip #3 from Wormhole) RNA enters the membrane (animation #5) Creates proteins Replicates itself Structure divides into two when surface area is too large (animation)