Four electron carriers, a, b, c, and d, whose reduced and oxidized forms can be distinguished spectrophotometrically, are required for respiration in a bacterial electron transport system. In the presence of substrates and oxygen, three different inhibitors block respiration, yielding patterns of oxidation states shown below (O = oxidized, R = reduced). What is the order of the carriers in the chain from substrates to O2, and where do the three inhibitors act?CarriersInhibitorsabcd1OORO2RRRO3ORR

18.3D: Electron Transport Chain and Chemisomosis