Chemists at The Scripps Research Institute (TSRI) have crafted a compelling new chemical blueprint for the origin of life on Earth. “This was a black box for us,” said Ramanarayanan Krishnamurthy, senior author of the new study. “But if you focus on the chemistry, the questions of origins of life become less daunting.” In a new study published in the journal Nature Communications, scientists explain how essential chemical reactions for supporting life could have occurred with ingredients that were very likely present on Earth four billion years ago. Their theory centers on what is known as the citric acid cycle, a system that enables every aerobic organism to release energy stored in its cells.
Previous efforts centered on the origins of life and the citric acid cycle envisioned early life incorporating the same molecules and chemical reactions in its cycle as those used by life today – molecules and chemical reactions that would not yet have existed four billion years ago. The team at TSRI crafted a new chemical recipe that could have worked with what existed long ago. They concluded that two non-biological cycles, the HKG cycle and the malonate cycle, could have been used to catalyze a primitive version of the citric acid cycle.
After testing these reactions, the team noted that the end products were amino acids and carbon dioxide, key organic compounds. As more organic compounds developed on early Earth, scientists at TSRI believe that they could have replaced the non-organic crude ingredients to create more complex and efficient organic chemical reactions. “The chemistry could have stayed the same over time, it was just the nature of the molecules that changed,” said Krishnamurthy. “The molecules evolved to be more complicated over time based on what biology needed.”