Looking at the table of redox potentials, what is one possible source of electro

Question

Looking at the table of redox potentials, what is one possible source of electrons for phototrophic bacteria that are not cyanobacteria?

Copyright © McGraw-Hill Education. Permission required for reproduction or display. Selected Biologically Important Half Reactions Table 102 Eo (Volts) Half Reaction 2H+ + 2e- H2 Ferredoxin (Fe3+) + e-ferredoxin (Fe2+) NAD(P)" + H+ + 2e- NAD(P)H s + 2H+ + 2e- H2S Acetaldehyde + 2H+ + 2e- ethanol Pyruvate" + 2H+ + 2e- lactate2- FAD + 2H+ + 2e- FADH2 Oxaloacetate'-+ 2H+ + 2e--> malate2- Fumarate2-+ 2H+ + 2e- succinate2_ Cytochrome b (Fe*) + e- cytochrome b (Fe2+) ubiquinone + 2H+ + 2e- ubiquinone H2 Cytochrome c (Fe3+) + e- cytochrome c (Fe2+) Cytochrome a (Fe3+) + e- cytochrome a (Fe2+) 0.42 -0.42 0.32 -0.27 -0.20 0.19 -0.18 0.17 0.03 0.08 0.10 0.25 0.29 Cytochrome a3 (Fe3) ecytochrome a3 (Fe2+) 0.35 0.42 0.44 NO3 + 2H + 2e NO2 + H2O NO2-+ 8H+ + 6e- NH4+ + 2H20 Fe3+ + e- Fe2+ 0713 2+2H+ + 2e-H2O 0.82 1 Eo is the standard reduction potential at pH 7.0 2 The value for FAD/FADH2 applies to the free cofactor because it can vary considerably when bound to an apoenzyme 3 The value for free Fe, not Fe complexed with proteins (e.g., cytochromes)

Explanation / Answer

Oxygenic photosynthesis:

6 CO2 + 6 H2O + light energy ------> C6H12O6 + 6 O2

Anoxygenic photosynthesis:

6 CO2 + 2 H2A + light energy ------> [CH2O] + 2 A + H2O

Source of electrons in anoxygenic photosynthesis:

Purple sulfur bacteria = S, H2S, Na2S2O3, S2O3- and Fe+2

Green and purple nonsulfur bacteria = H2

Rhodospirillum is a purple nonsulfur bacteria that uses H2 or propanol as electron donors.

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