An Enzyme-Free Krebs Cycle May Have Been Key Step in Origin of Life on a Harsh, Volcanic Earth Four (image) The Francis Crick Institute Share Print E-Mail Caption A set of biochemical processes crucial to cellular life on Earth could have originated in chemical reactions taking place on the early Earth four billion years ago, believes a group of scientists from the Francis Crick Institute and the University of Cambridge. The researchers have demonstrated in the lab an enzyme-free metabolic pathway that mirrors the important Krebs cycle present in living organisms today. It is sparked by particles called sulphate radicals under conditions similar to those on the harsh, volcanic Earth of four billion years ago. There has been much interest in how the first life forms developed in these conditions and how the biochemical processes necessary to sustain life could form from nothing. Credit Aleksej Zelezniak/Francis Crick Institute Usage Restrictions None Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.