146 PAUL WEISS 



cell the constituent molecular processes must not just happen, but must 

 take place according to a highly ordered plan of interrelations based on 

 orderly spatial distributions, orderly chronological sequences, and or- 

 derly ratios of rates. No model of a cell can be pertinent unless it takes 

 into account both the elementary processes and their organizational 

 frame. It is imperative, therefore, that we match research on the former 

 by an equally vigorous search for the physical basis of the latter. To 

 facilitate this task I have tried to sketch a sort of crude molecular 

 blueprint of the cell, in which the molecular phenomena are placed in 

 relation to the organisation of the cell as a unit. This picture is of 

 necessity diagrammatic, oversimplified, tentative, and full of blank 

 spaces, but it does serve to crystallize the problems. Most of it has 

 already been presented on an earlier occasion (54). 



Molecular Ecology 



Science advances not only by discovering new truths but also by 

 eliminating old errors. Most older cell concepts held to the view that 

 cellular organization is based on rigid structural frameworks of micro- 

 scopic order, but this view has been ruled out by modern cell research. 

 Cytoplasm behaves as a viscous liquid. It can be thoroughly mixed up by 

 stirring or centrifugation, and yet its countless chemical workshops will 

 continue to operate in good order, which implies proper spatial segre- 

 gation. No orderly microscopic array could have survived in the com- 

 mingled content; what has survived is a fixed set of conditions — the 

 rule, as it were — according to which the original order can be restored. 

 And where do those conditions reside ? Evidently they must be looked for 

 in those parts of the system which can preserve organization in the 

 shuffie. There are two categories of cell constituents that qualify under 

 this title, and they are of quite different order of magnitude, one molecu- 

 lar and the other supramolecular. The former consists of the large 

 organic molecules or molecular aggregates with their specific structure 

 and faculty to perpetuate this structure in the presence of the necessary 

 ingredients and appropriate sources of metabolic energy. The latter 

 consists of the existing surfaces and interfaces of microscopic or sub- 

 microscopic order, whose molecular linings are anchored by adsorption 

 or chemical fixation and thus better protected against random disrup- 

 tion. 



Organization within any sample space of a cell is then to be regarded 

 as a result of the counterplay between these two poles: the specific 



