Four electron carriers, a, b, c, and d, whose reduced and oxidized forms can be

Question

Four electron carriers, a, b, c, and d, whose reduced and oxidized forms can be distinguished spectrophotometrically, are required for respiration in a bacterial transport system. In the presence of substrates and oxygen, three different inhibitors block respiration, yielding the patterns of oxidation states shown in the table below. From these data, what is the order of electron carriers in the chain from substrates (meaning electron carriers) to O2 the terminal electron acceptor? 3. Effects of Inhibitors on Electron Carrier Oxidation levels Inhibitor 2 3 The symbols (+) and (-) indicate fully oxidized and fully reduced respectively 4. NADH oxidation For every NADH oxidized to NAD*, how many protons are transported to the intermembrane space of the mitochondria? a.

Explanation / Answer

3). The order of electron carriers in the chain from substrates to 02 the terminal electron acceptor is D, A, B, C.

4). When electrons from NADH move through the transport chain, about 10 H+ ions are pumped from the matrix to the intermembrane space, so each NADH yields about 2.5 ATP.

i.e.

Whereas the electrons from FADH2?, which enter the chain at a later stage, drive pumping of only 6 H+, leading to production of about 1.5 ATP.

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