Ion, Electron, and Proton Transport in Membranes: A Review of the Physical Processes Involved

Abstract

The physical concepts and problems associated with the understanding of ionic, electronic, and protonic transport in membrane structures are discussed. Ion transport is intimately associated with the existence of a transmembrane potential, and the contributions that ion concentration gradients, membrane surface charges, and surface redox reactions may give to this are described, together with the physical features required of ion channels and pores. An understanding of the coupling of electron transport processes to proton motive forces is a central task for modern bioenergetics, and some of the factors involved are discussed, as well as the physical mechanisms that control electron and proton transport processes in membrane structures. Other topics included are the dielectric properties of biological electrolytes, electronic induction, and dipole interactions in proteins, and proton transport in water, ice, and model systems.