A general system that can be used for the modelization of metabolic pathways dynamics in a heterogeneous milieu is presented. It consists in a set of nonlinear reaction-diffusion equations, involving a convection term originating from the transport of metabolites by an electric field. The functional study is focused on the existence, uniqueness, and positiveness of the solution. A numerical algorithm based on a mixed finite element method is presented, and illustrative examples are also given.