[Potential difference across the membrane of subcellular particles. V. Generation of potential differences by...

It is shown by the mehtod of penetrating ions that Site O and I of the respiratory chain of submitochondrial particles are able to generate a membrane potential of the normal value under anaerobic conditons. When succinate is an electron donor and ferricyanide-an acceptor (Site II), the oxygen addition sharply increases the membrane potential at pH above 7.5 and does not change or even decreases it in reaction conditions more acid than pH 6.5. The generation of the membrane potential at low pH and in the absence of oxygen is predicted by the chemielectric hypothesis and cannot be explained by the chemiosmotic one. Mitochondria usually generate the membrane potential without O2 at pH 7.5 in the presence of ferricyanide when the substrate concentration exceeds 5 mM.