 Employing stoichiometric models of metabolism and mass spectrometry methods with isotopic mass resolution, the transfer of moieties containing isotopic tracers from one metabolite into another can be elucidated, and information about the metabolic network thus derived.Metabolic flux analysis (MFA) has many applications such as determining the limits on the ability of a biological system in producing a biochemical such as ethanol and predicting the response to gene additions or knockouts.Metabolic flux analysis may use 13C to determine pathway fluxes, NMR techniques and mass spectrometry.