THE PROBLEMS 



The Subject 



Our subject is biological order, and the word order has hardly 

 been pronounced. As everyone knows, order is the fixed arrange- 

 ment present in the existing constitution of things. Order may also 

 be considered as a sequence or succession in space or time. Biological 

 order is all that, and it is especially a sequence in space a?2d time. 

 Biological order is dual, structural and functional, static and dy- 

 namic. Structural and functional orders are the complementary 

 aspects of the living being. A living being is a dual system of order. 

 We have to know what this dual system is. 



Metabolism 



A bacterium is seeded in a proper nutrient medium. Food is 

 taken in. Chemical reactions are performed. Syntheses take place. 

 This is metabolism. 



Today, almost everything is known concerning the synthesis of 

 the building blocks, or intermediary metabolism. One atom is 

 attached to another, a molecule is methylated, carboxylated, or 

 aminated (attachment of, respectively, a — CHo, a — COOH, or an 

 — NH2 group), and finally each atom is exactly where it belongs. 

 The synthesis of each building block is a stepwise process. As an 

 example, the biosynthesis of the amino acid tryptophan is depicted 

 in Figure 20. In order to synthesize tryptophan, each reaction has 

 to be catalyzed by a specific enzyme. Enzymes are specific proteins. 

 Some proteins have an enzymatic activity by themselves. Other 

 enzymes work only with the help of a specific coenzyme. Most of 

 the enzymes can be extracted from the cell and purified. It was 

 thus learned that a given enzyme performs only one chemical 

 reaction. 



In a biosynthetic chain of reactions, each reaction requires energy. 

 The energy needed for the syntheses is provided bv^ the oxidation of 

 food, for example sugar. The organism "burns" sugar, and the 

 energy obtained is stored as high-energy bonds, for example in the 

 form of adenosine triphosphoric acid. The oxidation of food and 

 the storage of energy involve a series of chemical reactions, each 

 one again mediated by a specific enzyme. 



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