Preface 



This volume on the control mechanisms in cellular processes 

 consists of papers presented at the symposium of the Society of 

 General Physiologists at its annual meeting in 1960. It will, we trust, 

 prove useful as a report to the diverse mechanisms now known to act 

 as reeulatorv svstems. 



Biologists have often felt that biochemists take a homogenized 

 and quite unregulated view of cellular events. In fact, the feeling 

 has been expressed that biochemists view cells simply as sacks full 

 of enzymes. There is, of course, some truth in this statement; the 

 elucidation of biochemical events has indeed required the use of cell- 

 free material. Such investigations, however, have proved singularly 

 rewarding; we now enjoy detailed knowledge of the precise mecha- 

 nisms involved in energy transfer, in the biosynthetic processes con- 

 cerned with the formation of substrate molecules, and in the synthesis 

 of such macromolecules as enzymes and nucleic acids. We have 

 come to an era in which fruitful consideration can be given not only 

 to the integration of separate biochemical events but to the coordi- 

 nate regulation of cellular biochemistry. In addition, consideration 

 can now be given these subject areas, in part at least, at the molecular 

 level. 



Multicellular animals have characteristic developmental stages. 

 Growth and development are intrinsic properties of biological sys- 

 tems; the biochemical characteristics of diverse differentiated cells 

 are clearlv different. Even in bacteria, biochemical differences have 

 been noted at different stages in their growth cycle. These are bio- 

 logical facts which must be accounted for, and the answer presum- 

 ably could in part be deduced from an understanding of the systems 

 which regulate cellular biochemistry. What are the regulatory sys- 

 tems known at present? 



A classic agent of cellular regulation is, of course, the gene. In 

 the past decade magnificent work from many laboratories has given 

 clear experimental proof that one action of genetic material is the 



III 



