  The macroscopic behavior of the solution of a coupled system of partial
differential equations arising in the modeling of reaction-diffusion processes
in periodic porous media is analyzed. Our mathematical model can be used for
studying several metabolic processes taking place in living cells, in which
biochemical species can diffuse in the cytosol and react both in the cytosol
and also on the organellar membranes. The coupling of the concentrations of the
biochemical species is realized via various properly scaled nonlinear reaction
terms. These nonlinearities, which model, at the microscopic scale, various
volume or surface reaction processes, give rise in the macroscopic model to
different effects, such as the appearance of additional source or sink terms or
of a non-standard diffusion matrix.
