A biomimetic membrane allows the active and selective transport of small molecules against their concentration gradient. The operation of such a membrane rests on the coupling of three fundamental phenomena: (i) reactant diffusion phenomena occurring in diffusion layers adjacent to a charged (+ or -) permeable membrane; (ii) catalytic reactions of a kinase and a phosphatase acting on either side of the membrane; (iii) interactions of electrical charges between the charged membrane and at least one metabolite involved in the reaction sequence (substrate or intermediate product). The active transport of glycerol-3-phosphate, carried out with an industrial reactor, is shown to illustrate this new membrane procedure, allowing the specific separation of small molecules.