84 PHOTOSYNTHESIS 



one mole of oxidizable substrate is much less than that re- 

 quired for the reduction of one mole of carbon dioxide. The 

 energy liberated from the oxidation of many molecules must 

 therefore be in some way 'pooled'. In Nitrosomonas, which 

 oxidizes ammonia to nitrite, and in Nitrobacter, which oxi- 

 dizes nitrite to nitrate, per gram molecule of carbon dioxide 

 reduced 35 gram atoms of nitrogen are oxidized in Nitro- 

 somonas whilst loi are utilized in Nitrobacter. Expressed in 



TABLE 5.4 



TABLE OF FREE ENERGIES OF REACTIONS OF BACTERIA 



Photosytitheses 



1. I of (12H2O+6CO2 -- C6H12O6+6H2O + 6O2) 

 i.e. 2H2O+CO2 -- (CH20)+H20+02 



2. 2H2S+CO2 ^ (CH26)+H26+2S 



3. 2H2+CO2 -^ (CH26) + HoO 



Chemosyntheses 



1. 2H2S + O2 - 2H2O+2S 



2. 2S + 3O2+2H2O ^ 2H2SO4 



Sum I and 2 (za). 2H2S+4O2 -^ 2H2SO4 



3. 2H2+O2 -- 2H2O 



4. NH40H+f02 -^ HNO2+2H2O 



5. HNOa+iOa -^ HNO3 



5a. NH4OH+2O2 -- HNO3+2H2O 



Note: AF°=—RTln K, where K is the equilibrium constant of the 

 reaction at 25°-: 8°, and is given for the standard state, i.e. Oo, CO2, 

 H2S, Ha, as gases i atm.; H2O liquid; S, (CH2O) [i.e. i(C6Hi206)] 

 solid; NH4OH, HNO2, HNO3, and H0SO4 as fully dissociated, each 

 ion I molar. Correction to actual conditions will not very greatly affect 

 the energy values for the oxidations. Making CO2 0-0003 atm. would 

 increase the energy required for i mol reduction by 1*365 x 3-52 =4-8 

 kg. cal.; while making O2 o-2 atm. would decrease the energ)^ from the 

 oxidations by 1-365 x 0-7 = 1-0 kg. cal. Dilution of NH4OH and of the 

 acids HNO2, HNO3 would affect both sides of the equation about 

 equally. 



