FRITZ LIPMANN 



carbohydrate. Therewith the view developed that catabolism con- 

 sists to a considerable extent of a conversion of potential energy of food- 

 stuffs into directly utilizable phosphate bond energy (7), and that, 

 through alternate attachment and release of energy-rich phosphate 

 bonds, catabolism and anabolism are knit together into a largely re- 

 versible reaction continuum. 



This new appreciation of aspects of the metabolic apparatus 

 which have hitherto been well concealed is beginning to affect our 

 general attitude toward problems of metabolic chemistry. The more 

 we recognize transformation of energy as a primary problem in meta- 

 bolic processes, the more are we compelled to treat metabolic proce- 

 dures for what they really are, namely, technical devices. In detail, 

 the manner in which the living organism solves the problem of energy 

 conversion is rather different from the technological methods employed 

 by man. But whether in the case of the organism or man, the ultimate 

 objective of energy conversion is the generation of energy in a utilizable 

 form. A fundamental analogy appears, indeed, between the in- 

 creasingly close dependence of our own daily life on electric current, 

 gas pipes, and a variety of motors and that of our body cells on food 

 and oxygen. In both instances the supply of energy is necessary to 

 maintain an organization, although most of the energy is ultimately 

 dissipated in the form of heat. 



In many respects a living cell is comparable to a chemical 

 factory. The design of chemical factories, from the standpoint of a 

 technologist, is based on a variety of technical principles (5). Only 

 the process proper remains chemistry, but its technical execution is 

 effected wholly by physicomechanical devices. This predominantly 

 mechanical manipulation of unit processes represents a most significant 

 difference between organismic chemistry and chemistry practiced by 

 man, for, in living cells, both process design and process execution are 

 based on chemical principles. Instead of the material being manipu- 

 lated successively in spatially separated compartments, cellular chem- 

 istry involves a harmonious series of consecutive reaction steps which 

 are brought about on a molecular scale by a host of catalysts, all present 

 together in the same reaction fluid. This difference in type of operation 

 tends to obscure the basic analogy of both procedures. 



Most metabolic processes classify among what the chemical 

 engineer calls "flow processes" (5), that is, procedures whereby streams 



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