The pH in the neighborhood of membranes generating a protonmotive force

Abstract

The chemiosmotic mechanism provides a way whereby energy inherent in a chemical combustion process is extracted and transduced: first into the energy of electron X volts of the electron redox system and second into proton X volts as protons are forced to leave the interior of the cell, creating an electro-chemical protonic potential (the protonmotive force). Here we consider the distribution of potential and pH across the membrane and the phases bathing the membrane in more detail. The distribution of hydrogen ions parallel to the surface is also described. It is shown that the voltage and pH gradients due to the proton extrusion occur near to the membrane (approximately 2 nm). This implies that the pH is much lower immediately outside the membrane than in the cytoplasm or in usual neutral growth or isotonic media. It provides a link between the points of view of Mitchell and Williams. It requires that literature models for the role of the protonmotive force in the maintenance of wall thickness in Gram-positive organisms, the adhesion of microbes to surfaces, and the transport of auxin in plants be modified.