Four billion years ago on Earth in bodies of water existed a closed chain of chemical reactions that led to the emergence of life.
It was discovered by American chemists of the research Institute of SCRIPPS. Article scientists published in the journal Nature Communications.
According to the researchers, a closed chain of chemical reactions was the equivalent of a modern tricarboxylic acid cycle (Krebs cycle), which could not occur in the precellular era.
The Krebs cycle occurs in the cells of every organism that uses aerobic respiration. It acetyl residues (СН3СО-) are oxidized to carbon dioxide.
In this form the energy-intensive ATP molecules and other compounds necessary for metabolism. However, substances involved in the Krebs cycle, could not remain stable in the environment that existed several billion years ago, before the first cells.
Chemists searched for molecules that could enter into a closed chain reactions and lead to the formation of the same substances as in the Krebs cycle. However, these substances were supposed to exist on the ancient Earth and be resistant to the conditions of the time.
Scientists believe that pre-cellular era to be the equivalent of the tricarboxylic acid cycle, which proceeded with the participation of other chemicals, unusual for biological systems. He, like the Krebs cycle, comprised of α-ketoacids, β-ketoacids and decarboxylation reaction, which produces carbon dioxide. However, it also formed the amino acids that contributed to the formation of a complex of enzymes necessary for the emergence of life.