Ubiquinone Q2 (CoQ(2)) is a member of the chemical class known as Polyprenylbenzoquinones. These are compounds containing a polyisoprene chain attached to a quinone at the second ring position. Ubiquione-2 has just 2 isoprene units. Normally in humans it has 10. Ubiquinone-2 is an intermediate in the synthesis of Ubiquionone 10. Ubiquionone is involved in cellular respiration. It is fat-soluble and is therefore mobile in cellular membranes; it plays a unique role in the electron transport chain (ETC). In the inner bacterial membrane, electrons from NADH and succinate pass through the ETC to the oxygen, which is then reduced to water. The transfer of electrons through ETC results in the pumping of H+ across the membrane creating a proton gradient across the membrane, which is used by ATP synthase (located on the membrane) to generate ATP. The first ubiquinone was isolated in 1957. Since that time, ubiquinones have been extensively studied in Japan, Russia, and Europe with research in the US beginning more recently. Popular press accounts claim that roughly 12 million Japanese use ubiquinones as the medication of choice for management of cardiovascular diseases, with more than 250 commercially available preparations. Ubiquinone is touted as an effective treatment of congestive heart failure (CHF), heart rhythm irregularities, high blood pressure, and in reducing injury to the heart muscle caused by lack of oxygen. Other claims include increasing exercise tolerance, stimulating the immune system, and counteracting the aging process. Ubiquinone has not been approved for therapeutic use in the US, but it is available as a food supplement. Ubiquinone may have applications in heart disease, especially CHF, although there is a lack of consensus. Studies in neurological disorders are less promising. Limited clinical trials have been conducted to support its widespread use for other conditions.