Fig. 3: Theoretical dependence of thermodynamic efficiency on force ratio.

The figure plots the dependence of efficiency (η) on the ratio between output (protonmotive) and input (oxidoreduction) forces normalised by the mechanistic (ideal) H⁺/e⁻ stoichiometry (Z) (see also ref. ¹⁴), according to Eq. (4), for four different degrees of coupling (q) as defined by Eq. (7). Example curves are given only for the “uphill” case where the redox reaction drives proton translocation. The thin blue lines show the approximate range of force ratios and efficiencies observed in State 3 of isolated rat-liver mitochondria (see Table 1). The area covered by the data is indicated as a blue rectangle.