NOVELTY - A fuel cell comprises a barrier separating an anode and cathode compartment and conveying protons from the anode compartment to the cathode compartment. The anode compartment comprises electron transfer mediator(s), redox enzyme and electron carrier(s). The cathode compartment comprises a cathode (45) which conveys the electrons to an electron acceptor composition in the cathode compartment.    USE - For powering electrical devices and fuel cell systems.    ADVANTAGE - The biocompatible membrane has improved stability to higher voltage differences across the anode/cathode barrier. The electron transfer mediator increased the efficiency of electron transfer to the electrode.    DETAILED DESCRIPTION - The fuel cell comprises a barrier separating an anode and cathode compartment and conveying protons from the anode compartment to the cathode compartment. The anode compartment comprises an anode (44) and dehydrogenase enzyme(s) effective to transfer electrons from a 1C compound to electron carrier(s). The anode compartment further comprises electron transfer mediator(s), redox enzyme and electron carrier(s). The cathode compartment comprises a cathode which conveys the electrons to an electron acceptor composition in the cathode compartment, when a conductive pathway to the electrode (I) is formed. The electron carrier(s) are selected to operate with the dehydrogenase enzymes and effective to deliver electrons to the anode or to deliver electrons to the mediator(s) or to the redox enzyme. The mediator(s) are selected to deliver electrons to the anode and redox enzyme is selected to deliver electrons to another electron carrier(s) (I). The electron carrier(s) (I) is selected to deliver the electrons to the anode.    INDEPENDENT CLAIMS are also included for the following:    (1) the production of electrical power, in which the electron carrier(s) are enzymatically reduced with electrons from 1C compound in anode compartment, the electrons are directly transferred from the carrier(s) to the anode, electrical current is transferred via an electrical conduit under an electrical load to the cathode and the electrons are transferred from the cathode to the electron acceptor composition;    (2) the formation of a biocompatible membrane incorporating a polypeptide associated with the biocompatible membrane, in which an aperture is contacted with a mixture of polypeptide, membrane-forming amphiphile and an amount of a solvent miscible with water and biomembrane phase effective to decrease viscosity sufficiently to facilitate biocompatible membrane formation and the solvent is removed by evaporation;    (3) a biocompatible membrane comprising a membrane-like barrier formed of triblock copolymer, where the copolymer comprises cross-linked polymer formed across an aperture with beveled edges;    (4) the preservation of the function of a polypeptide in the presence of non-aqueous solvents, where a solution of block copolymers in a solvent containing non-aqueous solvent(s) is formed and subsequently a polypeptide is added to the solution;    (5) a fuel cell system comprising the fuel cell adapted to operate with at least one liquid consumable and a fuel reservoir or a liquid fuel composition reservoir separated from the cathode compartment by porous membrane which is not wetted by either liquid fuel composition or a composition with which the cathode chamber operates, where the fuel reservoir comprises a liquid fuel composition separated from the anode compartment by a porous membrane which is not wetted by either the liquid fluid composition or a solvent/solution with which the anode chamber operates;    (6) the operation of a fuel cell, where fuel molecule or an electron acceptor molecule is consumed while operating the fuel cell, in which the fuel molecule or the electron acceptor molecule is transported via the vapor phase to a chamber in which the respective fuel molecule or electron acceptor molecule is consumed; and    (7) a device for metering a reactant concentrate comprising a chamber (I) for containing the reactant concentrate, a chamber (II) for receiving the reactant concentrate from the chamber (I) and a membrane separating the chambers (I,II), where the membrane comprises pores traversing from a side of the chamber (I) of the membrane to the side of the chamber (II) and internal conduit in the membrane effective to deliver gas to the pores.    DESCRIPTION OF DRAWING(S) - The figure shows a proton-conductive divider between an anode and a cathode chamber.    Anode (44)    Cathode (45)