recently discovered bacterium carries out ATP synthesis coupled to the flow of e
ID: 252472 • Letter: R
Question
recently discovered bacterium carries out ATP synthesis coupled to the flow of electrons through a chain of carriers to some electron acceptor. The components of its electron transfer chain differ from those found in mitochondria; they are listed below with their standard reduction potentials. 8. A Electron carriers in the newly discovered bacterium: ERD Electrons transferred Oxidant Reductant NAD flavoprotein b (FPb) NADH flavoprotein b -0.32 -0.62 (oxidized) (reduced) cytochrome c (Fe) Fe-S protein cytochrome c (Fe) +0.22 +0.89 Fe-S protein (reduced) lavoprotein a (reduced) in (oxidized) +0.77 flavoprotein a (FPa (oxidized) (a) Place the electron carriers in the order in which they are most likely to act in carrying electrons. (5) (b) Is it likely that O2 (for which E"-0.82 V) ?s the final electron acceptor in this organism? why or why not? (c) How would you calculate the maximum number of mol ATP that could theoretically be synthesized, under standard conditions, per pair of electrons transfered through this chain of carriers? (The Faraday constant, 3, is 96.48 kJ/V mol.) AG for ATP synthesis is +30.5 kJ/mol. (4)Explanation / Answer
a) Each electron carrier accepts an electron or an electron pair from a carrier with a less positive reduction potential and transfers the electron to a carrier with a more positive reduction potential. Thus, reduction potentials of electron carriers favor unidirectional electron flow -
Flavoprotein b -----> NADH ----> Cytochrome C ----> Flavoprotein a -------> Fe-S protein
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