FIGURE 4.
The various potential types of coupling between two metabolites are related to their conservation coefficient ratio limits Rmin and Rmax as shown. Two metabolites are: 1), fully coupled if the presence of one metabolite within conserved pools implies the presence of the other within the same conserved pools and vice versa, 2), partially coupled if they are always present within common conserved pools but their conservation coefficients are not fixed, and 3), directionally coupled if the presence of one metabolite within conserved pools implies the other and not vice versa.