The Biochemical Function of Cells 413 



of chlorophyll to total nitrogen in structures isolated from green plants grown 

 under indoor illumination is 0-3-0-35. In plants which receive enough energy 

 in the form of light, cyclophorase activity only manifests itself at low tempera- 

 tures, e.g. when the plant is grown under natural conditions in the autumn, when 

 the temperature is 2-12'C. Curves III, in Fig. 3, represent the distribution of 

 cyclophorase activity in the different fractions in plants grown under natural 

 illvmiination in the autimin. It does not differ from the results of the experiments 

 with partly and completely etiolated plants. In this case also, the second fraction 

 has the greatest activity; it is negligible in the first fraction and completely absent 

 from the third. 



In connection with the discovery of photosynthetic phosphorylation [82, 83] 

 which, along with the process of oxidative phosphorylation, is the mainstay of 

 the energy metabolism of the cell, the facts which we have put forward suggest 

 the idea that the enzymic system for oxidizing acids of the di- and tri-carboxyhc 

 acid cycle is brought into the process of metaboHsm under strictly determinate 

 conditions. When this happens the fimction of the system is obviously, in many 

 ways, dependent, not only on the character of the structures, but also on the 

 temperature conditions, the intensity of illumination and, as we shall show, the 

 qualitative composition of the light. 



In this connection the appearance and inclusion of the cyclophorase system 

 in the metabolism of the plant organism may be regarded as a characteristic 

 adaptive reaction of the organism, which enables it to maintain the necessary 

 level of energy imder conditions when the normal ways in which the plant 

 acquires energy are interfered with. 



Recently there has been accumulating an ever larger number of experimental 

 facts indicating the association of structure and function. Damage to the structural 

 organization affects, to a greater or lesser extent, the biochemical activity. The 

 data obtained by Oparin, Gel'man and Zhukova [84] provide fresh evidence in 

 this direction. These authors have shown that interference with the structural 

 integrity of the bacterial protoplast leads to both a slowing of the processes of 

 respiration and the incorporation of radioactive labels into the protein of the 

 protoplast. 



Owing to new biochemical evidence the concept of lyo- and desmo-enzymes 

 also needs to be made more precise. 



Generally known facts testify to the fact that the activity of two large groups 

 of enzymes, at least, is closely associated with a definite structural organization. 

 The activity of the enzymes of the cytochrome system and of the enzymes which 

 catalyse the oxidation of the acids of the di- and tri-carboxylic acid cycle is only 

 manifested in the presence of particular structural elements of the cell. 



The action of enzymes of the glycolytic system may be produced in solution 

 and therefore the part played by intracellular structures in the production of the 

 catalytic activity of this enzymic system has not been conclusively elucidated. 

 For some enzymes it has been definitely shown that in the boimd state they 

 lose their catalytic activity. It is interesting to remark, in this connection, that 

 the firmness of the bond between the enzyme and the proteins of the intracellular 

 structures changes according to the physiological state of the organism. For 



