The relationship between the rate of respiration and the protonmotive force. The role of proton conductivity.

It is shown by titrating a suspension of rat liver mitochondria with either ADP or an uncoupler that a specific rate of respiration may not have a unique associated value of the protonmotive force. Alternatively, a specific protonmotive force may not be associated with a unique rate of respiration. It seems that the rate of respiration and the protonmotive force are more sensitive to the agents used for the titrations than to each other. Such observations are not easily explained by the chemiosmotic hypothesis. It is, however, possible provided that the proton conductivities, i.e. the rates of dissipation of the protonmotive force, are considered to be different for each of the agents used to titrate the rate of respiration at the same protonmotive force, or vice versa.