Electron Transfer Chains are sets of reactions that lead to the synthesis of ATP in mitochondrion and chloroplasts of eukaryotic organisms. Energy produced in the form of ATP is used in the majority of endergonic reactions that enable processes to carry out the chemical reactions that sustain life. However the electron transfer chain is not yet fully understood, and every explanatory model is subject to constant revision, experimentation and refutation; thus is the nature of science. This report discusses a proposal presented in response to the prevailing model of electron transfer in the cytochrome bc1 complex. Although this complex has been intensely investigated, the cytochrome bc1 complex is yet to be fully understood with respect to the physical mechanisms that comprise the Q cycle, or the cycle that continually supplies the complex with electrons.

In a recent article published by Nature on February 12, 2004, entitled Reversible redox energy coupling in electron transfer chains (Dutton, et.al., 2004),a modification of electron flow in the cytochrome bc1 complex is proposed. The research group resolved millisecond reversibility in the electron-tunneling steps within the Q cycle. The proposal refutes certain aspects of previously proposed models of electron flow in this complex.
In this report, we will investigate the evidence of reversibility within the cytochrome bc1 complex, and the ramifications for electron transfer in this complex that result from the refined model.