Cellular respiration has a long research history at the interface between biology, chemistry, and physics. Research in this field spans the entire range from fundamental mechanistic and structural considerations on the atomic level to cell biology, physiology, and biomedicine. Our current concepts of cell respiration were established by the now classical work of Otto Warburg, 1 David Keilin, 2 and Britton Chance. 3, 4 Albert Lehninger 5 localized the process to the mitochondria of eukaryotic cells, and researchers at the Enzyme Institute in Madison, headed by David Green, first isolated and purified the complexes of the respiratory chain. 6 Efraim Racker and coworkers 7 identified and isolated the structures responsible for catalyzing oxidative ATP synthesis. Relatively soon it became clear that respiratory chain-linked ATP synthesis (ie, oxidative phosphorylation) is catalyzed by very similar membrane-bound protein complexes in all three domains of life, archaea, bacteria, and eukaryota, suggesting common universal mechanistic principles. The mechanism of coupling of respiratory electron transfer (eT) to the synthesis of ATP from ADP and inorganic phosphate (Pi) was mysterious for several decades, and was dominated by proposals of high-energy forms of cytochromes and other respiratory redox carriers that were thought to be chemical reaction intermediates in the process, 8 thus providing the required coupling between eT and phosphorylation. 9− 12 The proposal of the chemiosmotic hypothesis of oxidative and photosynthetic phosphorylation by Peter Mitchell in 1961 13 required no other intermediate than a transmembrane electrochemical potential difference of protons (a protonmotive force, pmf), and postulated that the transfer of reducing