The fumarate reductase enzyme complex is required for fumarate respiration. a quinone + succinate = a quinol + fumarate Binds 1 FAD covalently per subunit. Part of an enzyme complex containing three subunits: a flavoprotein (frdA), an iron-sulfur protein (frdB), and diheme cytochrome b (frdC). Belongs to the FAD-dependent oxidoreductase 2 family. FRD/SDH subfamily.