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ID: 209924 • Letter: C
Question
Copyright McGraw-Hill Education. Permission required for reproduction or display Selected Biologically Important Half Reactions Table 10.2 Eo (Volts) Half Reaction 2H 2eH2 Ferredoxin (Fe3+1+ e--> ferredoxin (Fe2+) NADP) +H +2 NAD(P)H S + 2H+ + 2e--> H2S Acetaldehyde + 2H+ + 2e- ethanol- Pyruvate-+ 2H+ + 2e- lactate?- FAD + 2H+ + 2e- FADH2 Oxaloacetate2_ + 2H + + 2e- malate2- Fumarate2-+ 2H+ + 2e- succinate? Cytochrome b (Fe3+) + e- cytochrome b (Fe2+) Ubiquinone + 2H+ + 2e- ubiquinone H2 Cytochrome c (Fe3+) + e- cytochrome c (Fe2+) Cytochrome a (Fe34) + e- cytochrome a (Fe2+) Cytochrome a3 (Fe3+1+ e- cytochrome 03 (Fe2+) 70.42 -0.42 0.32 0.27 -0.20 -0.19 -0.18 -017 0.03 0.08 0.10 0.25 0.29 0.35 0.42 0.44 0.773 0.82 NOg_ + 8h" + 6e- NH4+ + 2H2O Fe3+ + e- Fe2+ 2 + 2H+ + 2e- H2O 1 Eois the standard reduction potential at pH 7.0 2 The value for FAD/FADH2 appliles 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
Answer b) One possible source of electrons for phototrophic bacteria that are not cyanobacteria must be Hydrogen sulfide (H2 S).
Explanation - Cyanobacteria is aquatic, gram-positive and oxygenic phototrophic bacteria, also called blue-green algae which perform photosynthesis and liberate oxygen during photosynthesis. in this bacteria, water (H2O) is used as a source of oxygen and as an electron donor. while other types of bacteria are anoxygenic phototrophic bacteria which utilizes either elemental sulfur or hydrogen sulfide (H2S) as the source of the electron in the place of water.
so, based on the given table of redox potentials and the type of phototrophic bacteria (not cyanobacteria), one possible source of electrons is Hydrogen sulfide (H2S).