402 M. N. SISAKYAN 



biochemical function which also depends on the physiological state of the organ- 

 ism and is subject to regular change in the process of development. This fact is 

 of theoretical importance in that the biochemical property of any particular 

 structures should not be considered in isolation from the physiological charac- 

 teristics of the whole organism and the actual conditions of its existence. 



The method of differential centrifugation has given us the possibility of iden- 

 tifying various structmres, each of which is characterized by its size, its chemical 

 composition and its specific biological activity. Among these structures are the 

 nucleus, the plastids (which are peculiar to plant cells), the mitochondria and 

 the microsomes. There is also the residual centrifugate or dissolved fraction, 

 which contains various components derived from the structural elements during 

 the process of their separation. In the cells of the liver, which are often used for 

 the differential separation of structures, the difference in the diameters of the 

 particles is as follows: 



nucleus 50-100 //, mitochondria i //, microsomes 0*15 //. 



This paper does not give a review of the whole of the extensive literature on 

 the biochemistry of intracellular structures. We wish to limit the field of the 

 commimication to a few features of the uniformity and diversity which are to be 

 noticed in both the chemical composition and biochemical function of particular 

 structural elements of plant and animal cells. The paper does not try to give 

 an answer to all the questions which might arise out of such a review. We only 

 wished to present certain problems for assessment as this might lead to the 

 undertaking of new investigations in the direction indicated. 



CHANGES IN THE BIOCHEMICAL FUNCTIONS OF 



INTRACELLULAR STRUCTURES DEPENDING ON 



THE PECULIARITIES OF THE ORGANISM AND THE 



CONDITIONS OF ITS DEVELOPMENT 



Even if we have utterly inadequate information about the phylogenetic changes 

 in the biochemical properties of structures of a single type, some facts of interest 

 have been obtained in regard to the ontogenetic changeability of their bio- 

 chemical properties. As may be seen from Fig. i, the activity of the invertase 

 of the plastids of the sugar beet undergoes considerable change in tlie process 

 of the development of the individual organism. The maximal enzymic activity 

 in the chloroplasts of the sugar beet is to be seen in the period of intensive 

 accumulation of sugar, while the greatest activity of the plastids of the root of 

 this plant occurs at the end of vegetative grov^^h and the beginning of the period 

 of storage. These facts suggest that the biochemical function of any intracellular 

 structure is not laid down beforehand; it is not an unchanging property but, on 

 the contrary, it is subject to regular alteration depending on the internal state 

 of the organism and on the external conditions which surround it. This circum- 

 stance is of great importance in cormection with the study of the nature of the 

 intracellular localization of biochemical functions. In the light of new facts, as 

 has been said above, the concept of the localization of biochemical functions 



