Mitochondria and Reactive Oxygen Species

Fascination by the mitochondria, “the colonial posterity of prokaryocytes, probably primitive bacteria that into ancestral precursors of our eukaryotic cells and there,”1 stems from the above-mentioned nebulous theory of their origin, as well as from the realization of a very special role that they play in the of diverse diseases. organelles generate energy primarily in the form of electrochemical proton gradient (H), which fuels production, ion transport, and metabolism.2 Generation this universal energy currency, H, occurs through the of oxidative reactions conducted by the respiratory complexes at the ion-impermeable, almost cholesterolfree membrane. Reduced nicotinamide adenine dinucleotide the entry point to the complex I (reduced adenine dinucleotide:ubiquinone reductase), the reduced ubiquinol enters the respiratory chain in complex III (ubiquinol:cytochrome c [cyt-c] reductase) to cyt-c, the electron carrier to the complex IV, cyt-c . Each of these steps generates H by electrogenic of protons from the mitochondrial matrix to the space and is coupled to electron flow, thus the electric membrane potential of 180 to 220 and a pH gradient of 0.4 to 0.6 U across the inner membrane resulting in the negatively charged side of the membrane and alkaline matrix. Ultimately, H is converted into the influx of protons the matrix driving ATP synthesis or protein transport. In , these end points are necessary for the execution of 2 major enzymatic metabolic pathways within the mitochondrial : the tricarboxylic acid (TCA) oxidation cycle and fatty acid -oxidation pathway. This intricate system cellular functions is as elegant as it is vulnerable: every component of the system, from the electron chain complexes to the permeability properties of membranes, is a target for various noxious stimuli, some which can be generated within mitochondria themselves. list of these noxious stimuli is too long to be recounted , and the interested reader may refer to a recent excellent .3 These ancestral oxygen-using proteobacterial invaders with them into eukaryotic cells not only evolutionary but also potential side reactions, most dangerous which are “exothermic oxygen combustion and free emission.” This review is focused on one component the noxious mitochondrial pathway: reactive oxygen species (ROS) from a mitochondrial perspective, which has been extensively reviewed.4 Therefore, we shall the most recent findings but periodically offer historical .