Physical Constraints on Lateral Diffusion and Ubiquinone-Mediated Mitochondrial Electron Transport

Abstract

Recent investigations relating to the Random Collision Model of Mitochondrial Electron Transport [Hackenbrock, 1981; Hackenbrock et al., 1985, 1986a, b], have focused on elucidating the physical constraints on diffusion related to electron transport function in the inner membrane. This model rejects the concept that permanent assemblies or transient aggregates of redox components in the inner membrane are necessary to account for the sequence or maximum rate for the process of electron transport. In this diffusion-coupled process [Gupte et al., 1984] i.e. where all bimolecular redox reactions are preceded by one or more diffusion-based collisions between reacting redox partners, and where all redox partners are independent lateral diffusants [Sowers & Hackenbrock, 1981; Höchli et al., 1985], any factors that affect concentration or the rate of lateral diffusion should also affect the rate of electron transport. Towards these ends the experimental studies presented here relate the diffusion and collision of ubiquinone (Q) and its redox partners to electron transport as a function of temperature, concentration, and various agents added to the aqueous phase.