Transformer: The Deep Chemistry of Life and Death

by Nick Lane

I suspect that this reasoning applies to the Krebs cycle itself, which the biochemist Erich Gnaiger has compared to that ancient Egyptian (and later alchemical) symbol, the Oroboros, a serpent or dragon consuming its own tail.3 This mythical beast is usually interpreted as a symbol of eternal cyclic renewal, the cycle of life, death and rebirth. Gnaiger sees thermodynamic meaning too. The Oroboros cycle operates at 100 per cent efficiency: the energy for the serpent’s rebirth is captured entirely by consuming its own tail, with no external supply of energy. Life is plainly not a perpetuum mobile, so this conception of the Oroboros holds no direct meaning for the Krebs cycle, beyond both of them being cyclic. But it does speak to thermodynamic efficiency nonetheless. We have been talking about the driving force for metabolic pathways. We’ve seen that optimising the driving force means raising the levels of the substrates that enter the pathway while removing the end products. So the direction of a reaction that is close to equilibrium