Prebiotic Synthesis of Organic Compounds

Abstract

The heterotrophic hypothesis of the origin of life is now generally accepted. This involves the synthesis of simple organic compounds on the primitive Earth, the polymerization of these compounds, and the organization of the polymers into the first self-replicating organism. The need to synthesize simple organic compounds places constraints on conditions that prevailed on the primitive Earth. The temperature must have been low, O2 was absent, and the atmosphere was reducing. The most effective atmosphere for the synthesis of organic compounds is CH4, N2 or NH3, H2O. Experiments with less reduced atmospheres such as CO, N2 or NH3, H2O, H2 and CO2, N2 or NH3, H2O, H2 do give organic compounds but the yields are generally smaller and fewer compounds are obtained. CO and CO2 atmospheres without H2 give no organic compounds at all or very small yields. Prebiotic syntheses of amino acids, purines, pyrimidines, and sugars are now known. Organic compounds in carbonaceous chondrites are strikingly similar to those produced in laboratory syntheses with electric discharges.