Aerobic organisms transfer electrons from reduced fuel molecules to O2, forming H2O. Some anaerobic organisms use nitrate (NO3-) as an acceptor for electrons from reduced fuel molecules. Use the information in Table 14-4 to explain why aerobic organisms can harvest more free energy from a fuel molecule than can a nitrate-using anaerobe.
In Table 14.4

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Standard Reduction Potentials of Some Biochemically Important Half-Reaction: Half Reaction Cytochrome a (Fechrome as (Fe) 02 + 2H+ + 2 e-_H-02 Cytochrome a Fe)yochrome a (Fe) Cytochrome cyhrome c (Fe+) Cytochrome cı (Fe3+) + e cytochrome cl (Fe2+) Cytochrome b (Feytocome b (Fe2) (mitochondrial) Ubiquinone 2 H 2ubiquinol Fumarate2 H+ 2sccinate FAD 2 H2FADH2 (in flavoproteins) Oxaloacetate 2 H 2 emalate Pyrvate2H lactate Acetaldehyde 2 H 2ethanol FAD 2 H + + 2 e FADH2 (fee coenzyme) S 2 H2H2S Lipoic acid 2H 2dihydrolipoic acid NAD+ + H+ + 2 e NADH NADP+ + H+ + 2 e NADPH Cysteine disulfide 2 H 22 cysteine Acetoacctate 2 H 2-hydroxybutyrate o (V) 0.815 0.42 0.385 0.295 0.29 0.235 0.22 0.077 0.045 0.031 一0.040 -0. I 66 -0.185 -0.197 -0.219 -0.23 -0.29 -0.315 -0.320 -0.340 -0.346 -0.421 -0.515 -0.581 Acetate 3 H 2 ealdehyde H2o