The phenomenon of adjustment of metabolite flux, e.g. glucose that enters the anaerobic glycolysis pathway and exits as lactate, whatever its molecular mechanism. It reflects for each step of the pathway the range over which that step's activity can be modulated (regulability) and the effect this has on overall metabolic flux (control). Flux-control, metabolite-control, elasticity and response coefficients have been used to model and analyse the effects of substrate, inhibitor and allosteric effector concentrations.