70 THE SYNTHESIS OF FATS 



In the green leaf fat occurs : an examination of the ether 

 extract of the leaf tissue of the cabbage by Chibnall and 

 Channon * has shown it to contain fats whose acids are for 

 the most part unsaturated, namely linoleic and linolenic, but 

 the presence of oleic has not been established. The extract 

 contained no, or very little, phospholipid but the presence 

 was established of the calcium salt of a diglyceride phosphoric 

 acid of the formula 



CH a O-CO . R 



I 

 CHO-CO . R 



CH 2 0-P^-OH 



To this substance the authors give the name of phosphatidic 

 acid and suggest that it may be the precursor of lecithin and 

 kephalin in the animal body. These facts, however, do not 

 provide evidence of the photosynthetic origin of fats, nor 

 do the presence of elaioplasts, which apparently are degraded 

 chloroplasts. It must, therefore, be concluded that the facts 

 relating to the occurrence of fats and kindred substances in 

 chlorophyll-containing cells do not permit the drawing of a 

 definite conclusion in regard to the present problem, and, in 

 fact, there would appear to be no evidence to warrant the 

 conclusion that fats have a synthetic origin from raw materials 

 in the same sense as carbohydrates. For this reason their 

 origin must be sought out elsewhere : the proteins and the 

 carbohydrates are the obvious sources. 



Formation from Proteins. — Of the formation of fats from 

 proteins, little is known : the known facts indicate a relation- 

 ship between these two classes of compounds, but the signi- 

 ficance of this relationship is not clear. Evidence is not 

 wanting that proteins, in certain circumstances, may be con- 

 verted into fats ; but this evidence relates to the animal rather 

 than to the plant. 



In the plant there would appear to be some correlation, 



* Chibnall and Channon : " Bioohem. Journ.," 1927, 21, 225, 233, 

 479- 



