Response of pathways when production of B is localized. This figure shows how the steady state spatial distribution of the complexes AX and BX change in response to varying rates of production of nondiffusible X. A and X are produced at a uniform rate across the domain, while B is produced in a localized region (described by a sharp Gaussian profile centred around the middle of the domain). The spatial distribution of AX and BX as production of X changes is shown in a) and b), respectively. Localized production of B causes a very mild reduction in the production of AX around the centre and a sharp increase in BX there. Both A and AX are diffusible. In part c), only A is diffusible. Localized production of B causes a sharp reduction in the production of AX around the location at which B is produced.