The oxidized structure of CoQ, or Q, is given here:
The various kinds of Coenzyme Q can be distinguished by the number of isoprenoid side chains they have. The most common CoQ in human mitochondria is Q 10. The image above has three isoprenoid units and would be called Q 3.
If Coenzyme Q is reduced by one equivalent, the following structure results, a ubisemiquinone, and is denoted QH. Note the free radical on one of the ring oxygens.
If Coenzyme Q is reduced by two equivalents, the compound becomes a '''ubiquinol , denoted QH2''':
- CoQH2+ 2 Fe+3-cytochrome c → CoQ + 2 Fe+2-cytochrome c