The Krebs Cycle: Metabolic Reactions & Early Life

“A primeval version of the metabolic processes that all life uses to survive could have arisen spontaneously on Earth in the absence of enzymes, according to a new study.

This suggests that key parts of metabolism are older than life itself and could have emerged easily on early Earth.

Metabolism describes the complex network of chemical reactions that enable organisms to generate energy and the molecules they need to survive, grow and reproduce.

The Krebs cycle is at the heart of this network. It is a circular chain of reactions that generates precursors of amino acids and lipids used to build proteins and membranes, and molecules that help the cell to produce its energy.

But how such a complex cycle developed in the first place has remained a mystery.

Now Markus Ralser at the Francis Crick Institute in London and his colleagues have demonstrated that the Krebs cycle could have existed from the outset. The early life forms then simply adopted it, developing enzymes to make it more efficient, the team thinks.” (Geddes, 2017, p.11).


Geddes, L. (2017) Metabolic Reactions May have existed before Life. New Scientist. 18 March 2017.

Keller, M.A., Kampjut, D., Harrison, S.A. & Ralser, M. (2017) Sulfate Radicals Enable A Non-enzymatic Krebs Cycle Precursor. Nature Ecology & Evolution. 1, Article Number: 0083 (2017). doi:10.1038/s41559-017-0083.


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