BIOCHEMICAL SPACE 115 



the inviolate reproduction of all relevant constituents; a system 

 presumably indispensable for the cell to maintain itself in a state 

 of specificity. But the search for the nature of these controls has 

 been largely unsuccessful. It has, however, led to the construction 

 of many, often pretty, models which lately, since they are now 

 made of transparent plastic, have gained much in astral beauty. 



Our only refuge can be in vagueness, for instance, by pro- 

 posing some scheme of triangular relationships which may take 

 the childishly geometrical form shown in Fig. 10. This is, of 

 course, only one of many possible schemes for the interrelation 

 of the plastic cell constituents. No arrows have been placed quite 

 on purpose^^; and some of the soUd lines should probably be 

 broken lines or omitted entirely. The central role of ribonucleic 

 acid is based on what is now beginning to be known of the 

 metaboUc functions of certain conjugated ribonucleotides. One of 

 the main difficulties in all such schemes is that we do not yet 

 know whether the same agent is concerned with the selection and 

 alignment of the monomers and with the activation of their 

 linking into polymers. 



4. BIOCHEMICAL SPACE 



When we speak of the "flow" of biological information^^ or of 

 the "movement" of a given precursor, such as an amino acid or 

 phosphoric acid, into the various polymers^^- ^'^ found in the 

 several cellular elements, such as nuclei, mitochondria, micro- 

 somes, etc., we adhere subconsciously to a concept that, I believe, 

 is seldom formulated properly, namely, that of biochemical space. 

 It is probably a thankless job to estabUsh oneself as the Pindar 

 of negative attributes; but there are many things in nature that 

 are better described by a No than by a Yes. The cell, we might 

 say, is not a machine. It is not a mixture of soUds or even 

 crystals. It is not a system of solutions. Even in describing it as 

 an organized community of interfaces, of boundaries, we ap- 

 proach only a corner of the truth. 



What would be necessary for an understanding of biochemical 



References p. 125 



