ON THE PREBIOTIC ROLE OF IRON AND SULFUR

Thermodynamic data (Sillen, L. G.: 1966, Arkiv Kemi, 25, 159) indicate that there is little support for the idea that metabolic sulfur cycle s were involved in prebiotic and early life processes, since under red ucing conditions the 'equilibrium' concentration of sulfur in the prim ordial seas should have been very low, < 10(-8) M. However, it is sugg ested that metabolic sulfur cycles may have become important when oxyg en evolved, when iron(II) ions disappeared from the seas, and when lar ge amounts of sulfur were released from their iron sulfide sources.