Fig. 5. Three possible representations of a reaction network with three enzyme-catalyzed reactions and four reactants. (a) The most detailed picture includes three types of node - reactants (circles), reactions (ovals) and enzymes (squares) - and two types of edge - mass flow (solid lines) or catalysis (dashed lines). The edges are marked by the stochiometric coefficients of the reactants. (b) In the metabolite network all reactants that participate in the same reaction are connected; thus the network is composed of a set of completely connected subgraphs (triangles in this case). (c) In the reaction network, two reactions are connected if they share a reactant. A similar graph can be constructed for the enzymes as well.