BIOSYNTHESIS OF PROTEINS 263 



mathematical speculations, which attempt to reduce this 

 complicated biological phenomenon to comparatively simple 

 mathematical terms, just as Wrinch tried to postulate a struc- 

 ture for the globular protein on the basis of purely geo- 

 metrical considerations. However, we can already say with 

 certainty that nowhere in nature can we observe the forma- 

 tion of proteins by the direct ' birth ' of one molecule from 

 another identical one, as was imagined even quite recently. 

 The chemically individual proteins which have been isolated 

 do not arise of themselves by the ' division ' of molecules nor 

 by simple automatic autocatalysis. We can, in fact, only 

 olDserve the production of proteins in living bodies, and this 

 process requires the harmonious participation of a series of 

 systems including many different protein-enzymes. 



We can nowadays point to at least three categories of such 

 systems, the co-operation of which is indispensable for the 

 biosynthesis of proteins: i, systems which supply the energy 

 needed for the synthesis of the protein ; 2, catalytic (enzymic) 

 systems which create the kinetic conditions for the synthesis, 

 a definite relationship between the rates of the different 

 reactions ; 3, systems which determine the spatial organisa- 

 tion during the synthesis of the protein molecule. 



The method of synthesis of proteins from amino acids 

 seems to be common to the majority of present-day organisms, 

 though one cannot exclude the possibility that some pre- 

 formed peptides may be incorporated in the chains.^" As 

 was pointed out in the previous chapter, this method of 

 synthesis requires a certain expenditure of energ)% which 

 must be supplied to any system in which proteins are formed 

 directly. 



In all heterotrophic organisms the basic source of the 

 energy required for life seems to be the energy derived from 

 the anaerobic or aerobic breakdown of organic substances, 

 mainly carbohydrates (fermentation, glycolysis, respiration). 



The autotrophs also make extensive use of this method, 

 decomposing and oxidising the carbohydrates which they 

 have made by photo- or chemosynthesis. The various fer- 

 mentations, glycolysis and respiration, seem to be carried 

 through by very highly co-ordinated enzymic reactions. Their 

 realisation requires the presence of a very complicated system 



