GENERAL PRINCIPLES OF BIOCHEMICAL ENERGETICS 



145 



duced directly by the electrons of the substrate by a second carrier of 

 higher oxidation-reduction potential ; the carrier of the highest oxidation- 

 reduction potential is, of course, oxygen itself. 



This coupling of phosphorylations to oxidation-reduction during respi- 

 ration makes up the dynamo which transforms the energy of electron 

 transfer into energy-rich bonds of ATP. Without this coupling this energy 

 would be lost in the form of heat, and, in fact, a part of it is lost in this way. 

 We shall leave a detailed discussion of this aspect of energy until we come 

 to study the particular reactions involved. 



VI. THE CELLULAR DYNAMO 



The preceding has given us some idea of the lay-out of the cellular 

 machine and the function of its "dynamo" (Fig. 27). Details will be studied 

 later. This scheme is of general application for the provision of energy to 

 the living cell from the packets of chemical energy in the form of cellular 

 nutrients. However, there is another way of obtaining energy — by utilizing 

 the energy of the sun to perform biosynthesis. This dynamo functions by 

 coverting electromagnetic energy into chemical energy, but at the present 

 time its mode of operation is not so well understood as the chemical energy 

 dynamo described above. 



However, even if not generally accepted, the scheme proposed by Calvin 

 is of interest. The first stage of photosynthesis, is the conversion of water 

 into a reducing substance and half a molecule of oxygen : 



hv 



Heat 



HP 



Biosynthesis 



2[H] + JO, 



Mechanical 

 Work 



Active Bioluminescence 

 Transport 



/_ 



oxido-reduction 



Fig. 27 — General lay-out of the cellular dynamo (modified from Lipmann) 



