The article studies the effect of melafen on the physicochemical state of biological membranes, the electron transport in the mitochondrial respiratory chain, and the efficiency of oxidative phosphorylation. It examines the structural characteristics of membranes of sub-mitochondrial particles, rat liver microsomes and sugar-beet storage root mitochondria using paramagnetic spin probes. It reveals the significant changes in the energetics of liver and sugar-beet root mitochondria.