Answer:
The ubiquinone (coenzyme Q) can act as a bridge between a 2-electron donor and a 1-electron acceptor, in addition, since Q is a small and hydrophobic molecule, it can diffuse through the inner mitochondrial membrane and act as a shuttle reduction equivalents among other less mobile conveyors.
Explanation:
In relation to the mitochondrial respiratory chain, ubiquinone (Q) acts as a mobile electron acceptor between enzyme complexes, ensuring adequate electronic transport to oxygen. On the other hand, it also participates in the generation of the chemosmotic gradient of protons through the mitochondrial inner membrane, so it has a main function in the synthesis of ATP. In addition, ubiquinone interacts with other molecules that provide electrons, such as the electron transfer protein of β-oxidation of fatty acids. For this key function in energy metabolism to develop properly, it is necessary not only the presence of ubiquinone in adequate concentrations, but also the integrity of the inner membrane of the mitochondria (phospholipids and ubiquinone binding proteins that are part of the structure of the respiratory chain). Electronic transport through ubiquinone is carried out thanks to the interconversion of this molecule in its oxidized (Q; electron-acceptor), reduced (QH2: electron donor) and ubisemiquinone (Q-) forms, and the ability to displacement of ubiquinone through the phospholipid environment of the inner membrane of the mitochondria.
