CoQ is a component of the mitochondrial electron transport chain (ETC), where it plays a role in oxidative phosphorylation, a process required for the biosynthesis of adenosine triphosphate, the primary energy source of cells.
CoQ is a lipophilic molecule that is located in all biological membranes of human body and serves as a component for the synthesis of ATP and is a life-sustaining cofactor for the three complexes (complex I, complex II, and complex III) of the ETC in the mitochondria. CoQ has a role in the transport of protons across lysosomal membranes to regulate pH in lysosome functions.
The mitochondrial oxidative phosphorylation process takes place in the inner mitochondrial membrane of eukaryotic cells. This membrane is highly folded into structures called cristae, which increase the surface area available for oxidative phosphorylation. CoQ plays a role in this process as an essential cofactor of the ETC located in the inner mitochondrial membrane and serves the following functions:
* electron transport in the mitochondrial ETC, by shuttling electrons from mitochondrial complexes like nicotinamide adenine dinucleotide (NADH), ubiquinone reductase (complex I), and succinate ubiquinone reductase (complex II), the fatty acids and branched-chain amino acids oxidation (through flavin-linked dehydrogenases) to ubiquinol–cytochrome-c reductase (complex III) of the ETC: CoQ participates in fatty acid and glucose metabolism by transferring electrons generated from the reduction of fatty acids and glucose to electron acceptors;
* antioxidant activity as a lipid-soluble antioxidant together with vitamin E, scavenging reactive oxygen species and protecting cells against oxidative stress, inhibiting the oxidation of proteins, DNA, and use of vitamin E.
CoQ also may influence immune response by modulating the expression of genes involved in inflammation.