# Futile cycle

A Futile cycle is when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than wasting energy.[1] For example, if glycolysis and gluconeogenesis were to be active at the same time, glucose would be converted to pyruvate by glycolysis and then converted back to glucose by gluconeogenesis, with an overall consumption of ATP.[2] Futile cycles may have a role in metabolic regulation, where a futile cycle would be a system oscillating between two states and very sensitive to small changes in the activity of any of the enzymes involved.[3] The cycle does generate heat, and may be used to maintain homeostasis.

## Glycolysis/Gluconeogenesis

This futile cycle is

${\displaystyle ATP+H_{2}O{\rightleftharpoons }ADP+P_{i}+heat}$

## References

1. Schwender J, Ohlrogge J, Shachar-Hill Y (2004). "Understanding flux in plant metabolic networks". Curr Opin Plant Biol. 7 (3): 309–17. PMID 15134752.
2. Boiteux A, Hess B (1981). "Design of glycolysis". Philos Trans R Soc Lond B Biol Sci. 293 (1063): 5–22. PMID 6115423.
3. Samoilov M, Plyasunov S, Arkin A (2005). "Stochastic amplification and signaling in enzymatic futile cycles through noise-induced bistability with oscillations". Proc Natl Acad Sci U S A. 102 (7): 2310–5. PMID 15701703.