FIGURE 8.

Schematic depiction of the transfer of the two electrons and two protons of a ubiquinol at the Q_P pocket when oxidized in the bc₁ complex. The first electron and proton are in green, and the second electron and proton are in red. The purple arrow indicates oxygen molecules that are diffused to the Q_P pocket. Dashed arrows indicate plausible electron, proton, and superoxide transfer routes. Q_P and Q_N denote quinol oxidation and the quinone reduction pocket. QH₂, ubiquinol; TM, transmembrane region; ISP, Rieske iron-sulfur protein.