Editing Electron transport chain (section)

====Complex II====
In [[Respiratory complex II|Complex II]] ([[succinate dehydrogenase]] or succinate-CoQ reductase; {{EC number|1.3.5.1}}) additional electrons are delivered into the [[quinone]] pool (Q) originating from succinate and transferred (via [[Flavin adenine dinucleotide|flavin adenine dinucleotide (FAD)]]) to Q. Complex II consists of four protein subunits: succinate dehydrogenase (SDHA); succinate dehydrogenase [ubiquinone] iron–sulfur subunit mitochondrial (SDHB); succinate dehydrogenase complex subunit C (SDHC); and succinate dehydrogenase complex subunit D (SDHD). Other electron donors (e.g., fatty acids and glycerol 3-phosphate) also direct electrons into Q (via FAD). Complex II is a parallel electron transport pathway to Complex I, but unlike Complex I, no protons are transported to the intermembrane space in this pathway. Therefore, the pathway through Complex II contributes less energy to the overall electron transport chain process.{{cn|date=January 2025}}