ENERGY SUPPLY OF THE CELL 71 



Rhizobium grow as far as 10 mm. below the surface 

 in an agar medium oxidized by addition of 0.015% 

 KMn04 while in the untreated; normal medium, they 

 grew on the surface only. 



For thermodynamic reasons, processes of type (3) can 

 take place only if the energy liberated by dehydrogena- 

 tion (oxidation) is greater than that required for hydro- 

 genation, or if the total energy gain of the acceptor is 

 smaller than the total energy loss of the donator. This 

 eliminates a priori a number of processes as impossible. 



Putter, in his book on comparative physiology (1911) 

 has computed the calories produced by 1 gm. of oxygen in 

 oxidizing various organic compounds. Table 9 is an 

 extract from Putter's data. The energy liberated is 

 very uniformly 3.3 calories per 1 gm. of oxygen, regard- 

 less of the type of compound oxidized. Only oxalic 

 acid deviates considerably from this average. 



With inorganic compounds, the liberated energy 

 varies greatly. Table 9 gives a few examples, computed 

 also on the basis of energy per gram of oxygen. It is 

 very evident which compounds are good hydrogen 



Table 9. — Calories Liberated by 1 Gm. of Oxygen 



A. In the oxidation of inorganic compounds 



Kg. calories per gm. 

 oxygen 



H2 + O = H2O 4.25 



H2O + O = H2O2 -1.44 



C + O = CO 1.80 



CO + O = CO2 4.24 



HoS + = H20+S 3.87 



HoS +40 = H2SO4 ^ 3.18 



S + H2O + 30 = H2SO4 2.96 



NH3 +30 = HNO2 + H2O 1.63 



HNO2 + O = HNO5 1.16 



H + N +30 = HNO3 1.02 



