EXPERIMENTAL ANALYSIS 



macromoleciilar complexes containing phospholipines and pentose 

 nucleoproteins are characteristically found in the cytoplasm of cells. 

 The notion that the cell cytoplasm contains a few microscopically 

 visible formed elements, such as the mitochondria, but consists in the 

 main of a structureless matrix in which a bewildering number of sub- 

 stances is more or less randomly distributed has been giving way to a 

 concept of a high degree of organization at the submicroscopic level. 

 NiLSSON^^^ and Commoner^^^ have drawn attention to the importance 

 of cell structure in the orientation of cellular metabolic systems, 

 especially those concerned with oxidations. This idea had already been 

 put forward by Warburg^^" in 19 13; he was perhaps the first to insist 

 on the importance of structural arrangement of cell constituents in 

 respiration. Before anything was known about the fine structure of the 

 ground substance of the cytoplasm, Hopkins^ ^^ discerned that 'although 

 the microscope may detect no heterogeneity in the cytoplasm', 'the 

 micelles or particles which form the internal phase in the cytoplasm 

 must be diverse in respect of their surfaces, and a proportion, probably 

 no small proportion, of these surfaces, must have catalytic properties'. 

 Hopkins envisaged the possibility that the catalytic agencies in cells 

 might, because their activities depended so completely on configuration 

 and localization in a structural framework, be incapable of isolation. 

 The centrifuged sediment of a muscle suspension was however shown by 

 Banga^^^ to possess respiratory enzyme activities. At about this time 

 Claude^^^ first isolated macromolecular particles from normal and 

 malignant tissues, and was followed by Kabat and Furth^^* and by 

 Stern^^^"^^'^ and others. Stern considered that the macromolecular 

 material, though heterodisperse, consisted of 'subcellular functional 

 units' and believed 'that the active groups of the various component 

 catalysts are arranged in or on them in an orderly fashion so as to 

 ensure a smooth functioning of the highly complex process of cell 

 respiration'. The dependence of enzyme activities on the structural 

 integrity of cytoplasmic particles is now well established (Schneider 

 and HoGEBOOM^^^). Claude^^ 159 classified cytoplasmic particles into 

 two broad categories: 'large granules', precipitable at 2,000 X g in 25 

 minutes and of size 0-5 to 2-0^; and 'microsomes' brought down at 

 18,000 X ^ in 90 minutes, with a size range of 100 to 20om/(. Enzymatic 

 activities of many kinds have been found associated with the particles, 

 and in general the larger the particle size, the higher the probability of 

 finding a greater variety of enzymes. The size of particle isolated is a 

 function of the conditions of centrifugation, and Claude,^^^ while he 

 supports the idea that there are several distinct types of particle in most 

 cells, noted that the mitochondria and large granules stood at the end 

 of a continuous series of cytoplasmic elements. Chantrenne^^^ demon- 

 strated, in extracts of mouse liver, a continuous range of particle size, 



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