FIG. 1.
Schematic representation illustrating mechanisms of free radical(s) generation by ETC, TCA cycle, and enzymatic pathways in the mitochondria leading to the detoxification of O2•− and H2O2. Black dashed thick arrows show the path of electron transport from NADH or FADH2 to O2. Red dashed straight arrows indicate O2•− generated due to RET from FADH2-linked succinate to C-I. Dashed thin black arrows indicate the sites in the mitochondria mediating H2O2/O2•− generation. Positive and negative charges on the membrane denote the membrane potential (ΔΨm). Black dashed circle represents TCA cycle, which generates substrates for the ETC for generating •OH or O2•− radicals. RET is shown in red. α-KG, α-ketoglutarate; Δψm, mitochondrial membrane potential; C-I, complex I; C-II, complex II; C-III, complex III; CoQ, coenzyme Q; cyt c, cytochrome c; ETC, electron transport chain; FAD, flavin adenine dinulceotide; GPx, glutathione peroxidase; H2O2, hydrogen peroxide; O2, oxygen; O2•−, superoxide; •OH, hydroxyl radical; ONOO−, peroxynitrite; RET, reverse electron transport; SOD, superoxide distmutase; TCA cycle, tricarboxylic acid cycle/Krebs cycle. Color images are available online.