Figure 1.

Mitochondrial generation of ROS.

The electrons generated from the metabolic intermediates lead to the production of ROS at specific location in the mitochondria (mtROS or mROS). The generation of the ROS mainly takes place during the process of oxidative phosphorylation at the ETC located on the inner mitochondrial membrane. Complexes I, II, and III play a pivotal role in the generation of ROS. Release of electrons at complexes I and III from electron transport chains leads to partial reduction of oxygen to form a free radical such as superoxide. Superoxide is released to the intermembrane space from complex III, owing to generation from ubisemiquinone at the outer ubiquinone-binding site (Qo) of complex III. Subsequently, superoxide is quickly dismutated to hydrogen peroxide by 2 dismutases including superoxide dismutase 2 (SOD2). The H₂O₂ is degraded in the matrix by glutathione peroxidase (GPx). ETC indicates electron transport chain; ROS, reactive oxygen species.