[Potential difference across the membrane of subcellular particles. II. Proton channels in oxidative...

A photo-electrochemical hypothesis of cyclic photophosphorylation in chromatophores suggests that electrons, thrown out by light from the reaction center, came back via the electron carrier chain within the hydrophobic part of the membrane taking up H+-ions through the entrance H+-channels. H+-ions and electrons are transferred to quinones or semiquinones which are transformed into semiquinones or hydroquinones accordingly. They release H+-ions into output channels, while the electrons are transferred to the next electron carrier. At non-cyclic photophosphorylation of the chloroplast the second photosystem takes electrons from water via primary donor and releases the H+-ions into the proton channels. After receiving an electron the oxidase takes up H+ through the H+-channels and gives the electron and H+ to O2. A direct method of the experimental check up of the electrochemical hypothesis is described.