Complex III (also known as cytochrome bc1 complex), is the third critical component of the electron transport chain (ETC) in oxidative phosphorylation. It transfers electrons from ubiquinol (QH2), the reduced form of ubiquinone (Q), to cytochrome c, a mobile electron carrier in the mitochondrial intermembrane space. Transfer of electrons through Complex III generates a proton gradient across the inner mitochondrial membrane, contributing to the establishment of the proton motive force necessary for ATP synthesis by ATP synthase. Complex III receives electrons from ubiquinol (QH2), generated during the electron transfer from Complex I and Complex II to ubiquinone (Q) in the ETC. Ubiquinol binds to the Qo site of Complex III, where the transfer of electrons takes place. The electrons from ubiquinol are transferred through a series of iron-sulphur (Fe-S) clusters and heme groups within Complex III. The iron-sulphur clusters facilitate the stepwise transfer of electrons, whilst the heme groups, including cytochrome b and cytochrome c1, play a critical role in accepting and donating electrons during the process. As electrons pass through Complex III, protons are pumped across the inner mitochondrial membrane from the matrix to the intermembrane space. This process is coupled to the transfer of electrons and contributes to the establishment of the proton motive force, which is essential for ATP synthesis. Complex III uses a unique mechanism known as the Q cycle to pump protons. During the Q cycle, the binding of two molecules of ubiquinol results in the oxidation of one molecule and the reduction of the other, leading to the release of two molecules of ubiquinone and two molecules of ubiquinol. This process allows for the translocation of protons across the membrane. After the transfer of electrons through the iron-sulphur clusters and heme groups in Complex III, they are eventually transferred to cytochrome c, a small heme-containing protein in the intermembrane space. Cytochrome c serves as a mobile electron carrier, shuttling electrons between Complex III and Complex IV (cytochrome c oxidase). The transfer of electrons from cytochrome c to Complex IV is the final step in the electron transport chain. In Complex IV, electrons are used to reduce molecular oxygen (O2) to water (H2O), releasing the energy needed to pump additional protons across the inner mitochondrial membrane. In addition to its individual form, Complex III can also form supercomplexes with Complex I and Complex IV, creating what is known as the respirasome. Supercomplex formation enhances the efficiency and stability of electron transfer within the ETC, facilitating the flow of electrons and minimizing the production of reactive oxygen species (ROS). Dysfunction of Complex III has been associated with various human diseases, including mitochondrial disorders and neurodegenerative conditions. Mutations in genes encoding subunits of Complex III or factors involved in its assembly can lead to impaired electron transfer and reduced ATP production. Additionally, Complex III is a significant source of ROS production during oxidative phosphorylation, and defects in its function can result in increased ROS levels and oxidative stress. We provide a wide product catalogue of research reagents for investigating Complex III, including UQCRFS1 antibodies. Explore our full Complex III product range below and discover more, for less.