Guilliermond - Atkinson — 26 — Cytoplasm 



proteins of the nucleus are basophilic while those of the cytoplasm 

 are acidophilic. 



Lipides:- As is known, lipides include substances of very varied 

 chemical constitution which fall into one group by reason of their 

 common properties: solubility in ether, chloroform and benzene 

 as well as diverse histochemical characteristics. 



Lipides, but for rare exceptions, seem to be exclusively con- 

 tained in the cytoplasm. Analysis of plant tissues shows that they 

 constitute a considerable proportion of the cytoplasm, 15-25%, and 

 among these are the simple lipides (lipides ternaires) and the com- 

 pound lipides. The simple lipides^ include on one hand the glucer- 

 ides or true fats, esters of glycerol and a fatty acid, and on the 

 other, the sterols^ composed of alcohols of high molecular weight 

 which can be esterified by fatty acids. The compound lipides are 

 subdivided into phospholipides, esters resulting from the combina- 

 tion of an alcohol, inositol, with phosphoric acid and the phospho- 

 aminolipides, represented by lecithins, which like the glycerides, are 

 esters of glycerol but contain nitrogen and phosphorus and in which 

 two alcohol linkages of glycerol are combined, each to a molecule 

 of fatty acid, the third being united to a molecule of phosphoric 

 acid itself linked to choline and sometimes to betaine, a substance 

 possessing both the alcohol and the amino function. 



A considerable proportion of protoplasmic lipides represent re- 

 serve products which accumulate at certain periods in the life of 

 the cells and are later consumed. Such is the case for most of the 

 glycerides and perhaps also for certain lecithins. Sterols and 

 lecithins are also found in the vacuoles where they are products of 

 metabolism whose role is not yet known. But the work of Mayer 

 and SCHAEFFER on animal cells, the results of which certainly apply 

 to plant cells, has shown that a notable part of these lipides repre- 

 sent an essential constituent of the cytoplasm. They are, there- 

 fore, an integral part of living matter. 



These lipides are sometimes refractive globules in the cyto- 

 plasm (Fig. 9), or they are sometimes represented in the plastids 

 and chondriosomes but it seems as if a considerable proportion of 

 them were combined with the cytoplasmic proteins as compound 

 lipoproteins. It is difficult to detect them, for, being combined 

 with the proteins, they are invisible and constitute what is known 

 as masked lipides. Their existence may be demonstrated either by 

 histochemical analysis of certain tissues or by chemical analysis. 



It is by this chemical analysis that notable quantities of lipides 

 have been revealed in tissues which do not show any in the state 

 represented in Figure 9 and in which no trace of them is found with 

 ordinary histochemical methods. Among these masked lipides there 

 are some, however, which are united to the proteins in an unstable 



' The translator thinks these substances are probably complex as they contain both the 

 compound and derived lipides of Bodansky's classification. Bodansky. M. Introduction to 

 Physiological Chemistry. Wiley and Sons, New York. 1938. 



^ Translator's note. The sterols actually occur partly as free alcohols and partly as esters 

 of fatty acids. 



