Futile cycle

A Futile cycle is when two metabolic pathways run simultaneously in opposite directions and have no overall effect other than wasting energy. 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. 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. The cycle does generate heat, and may be used to maintain homeostasis.

Glycolysis/Gluconeogenesis
This futile cycle is $$ATP + H_2 O {\rightleftharpoons} ADP + P_i + heat$$