a) Calculate the G°’ for the Nitrogenase reaction: (see table 3.5 below) 8 Ferre

Question

a) Calculate the G°’ for the Nitrogenase reaction: (see table 3.5 below)
8 Ferredoxin(spinach) (Fe2+ ) + N2 + 10 H+ 8 Ferredoxin(spinach) (Fe3+) + 2 NH4+ + H2

b) How would the G°’ of the reaction change when it is coupled to the hydrolysis of 16 ATPs?

c) Why does the reaction require ATP hydrolysis?

TABLE 3.5 Standard Reduction Potentials for Several Biological Reduction Half-Reactions Redudion Half-Reaction 0.816 2 H+-+ 2e Fe3+ e 0.77 Photosystem P700 0.430 NO, 2 H+ 2 NO2 H20 0.421 0.365 Cytochrome f(Fe3+) e cytochrome f(Fe2+) Cytochrome ay (Fest) e cytochrome ay(Fe2 0.350 Cytochrome a(Fest) e cytochrome a 0.290 0.280 Rieske Fe-S(Fe3+) e Rieske Fe-S (Fe2 Cytochrome c (Fe e r cytochrome c (Fe 0.254 Cytochrome ch (Fe3+) e cytochrome c (Fe 0.220 0.190 UQH (UQ- coenzyme Q) 0.060 UQ 2 H+ 2 e UQH2 Cytochrome bi (Fe3+) e cytochrome bH (Fe 0.050 0.031 Fumarate 2 H 2 er succinate 0.030 Cytochrome bs(Fe3+) e cytochrome bs (Fe 0.020 0.003-0.091* FAD) 2 H+ 2 e (FADH2] Cytochrome bu(Fe3+) e cytochrome b (Fe2 0.100 Oxaloacetate 2H++ 2e malate 0.166 Pyruvate 2H 2 e lactate 0.185 Acetaldehyde 2 H 2 e ethanol 0.197 FMN 2 H+ 2e FMNH 0.219 FAD 2H++ 2e FADH 0.219 Glutathione (oxidized 2 H 2e 2 glutathione (reduced) 0.230 Lipoic acid 2 H Lt 2 e dihydrolipoic acid 0.290 1,3-Bisphosphoglycerate 2 H 2 e 0.290 glyceraldehyde 3-phosphate Pi 0.320 NAD 2H+ 2 e NADH H NADP+ 2H+ 2e NADPH H 0.320 0.340 Lipoyl dehydrogenase FAD 2 H 2 e lipoyl dehydrogenase FADH2] a-Ketoglutarate CO2 2 H 2 e isocitrate 0.380 2 H+ 2 e 0.421 Ferredoxin (spinach) (Fen t e ferredoxin (spinach) (Fe 0.430 Succinate CO2 2 H 2 e a-ketoglutarate H20 0.670

Explanation / Answer

Answer-

G is the change in Gibbs free energy , whic is negative for exothermic reaction and can be negative only for spontaneous reactions.

And it is positive for endothermic reaction.

G = H - TS

here H is the chane in heat, S is the change in entropy, T is the temerature

The Ferredoxin (spinach) Fe+2 to Fe+3 = -0.430

b)

The raction with ATP= 1

The change in Gibbs free energy G is negative for exothermic reaction and can only be negative for spontaneous reactions. However, the activation energy required would still cause this reaction to occur slowly

c)

To perform cellular work, ATP gets hydrolysed. The energy from hydrolysis of ATP was stored in chemical energy that has been stored in the high-energyphosphoanhydride bonds in adenosine triphosphate (ATP) ..

ADP is compined with a inorganic phosphate to form ATP in the reaction

ADP + Pi + free energy ----> ATP + H2O

This energy usually released by coupling with exergonic reaction of ATP with the endoergonic reaction.

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