Electrochemistry: Studying metabolism with galvanic cells

Researchers recently reported the design of a glucose/${\text{O}}_2$‍ galvanic cell. A description of the cell is provided below. It may be helpful to draw out the cell.

Essentially, the researchers used enzymes naturally found in the body to facilitate the oxidation and reduction reactions involving glucose and oxygen, respectively, in the two separate half cells of the galvanic cell. Because only one enzyme was used in the oxidation of glucose, the oxidation of glucose was not complete (i.e. no carbon dioxide was produced).

A carbon-based metal served as an anode and cathode in both cells; each electrode was attached by a wire that stretched between the two half cells to serve as a passage for electrons. The shape and small size of the pores in the electrodes allow electron transfer to occur more efficiently with biological enzymes whose functional groups were buried deep inside the protein. The flow of electrons, or current, created by this galvanic cell was enough to power a Light-Emitting Diode inserted into the wire circuit between the two half cells, demonstrating its electrical-powering abilities.

Reuillard, B. et al. High power enzymatic biofuel cell based on naphthoquinone-mediated oxidation of glucose by glucose oxidase in a carbon nanotube 3D matrix. Phys. Chem. Chem. Phys. 15, 4892–4896 (2013).