Elucidates the topological and flux connectivity features of genome-scale metabolic networks and enables the global identification of blocked reactions, equivalent knockouts, and sets of affected reactions. The FCF computational procedure allows one to determine whether any two metabolic fluxes, v1 and v2, are (i) fully coupled, if a non-zero flux for v1 implies a non-zero, but also a fixed flux for v2 and vice versa; (ii) partially coupled, if a non-zero flux for v1 implies a non-zero, though variable, flux for v2 and vice versa; or (iii) directionally coupled, if a non-zero flux for v1 implies a non-zero flux for v2 but not necessarily the reverse. Due to its wide range of features and applicability to genome-scale networks, the FCF procedure provides a useful framework for both modelers and experimentalists seeking to extract biologically meaningful information from metabolic reconstructions.