Fa ts 



25 



catalyses the union of cytidine-diphospho-choline and diglyceride 

 with the production of lecithin. In this form most of the fat of the 

 normal liver, and quite likely of other, cells is stored until required 

 for metabolic purposes; much is liberated from the cells of the 

 liver for utilisation and storage elsewhere in the body. These 

 mechanisms, which are encountered both in living cells and isolated 

 enzyme systems, are summarised in the scheme of Kennedy (1957) 

 to whom we owe so much of this information. 



ATP + Glycerol 



rOH 

 hOH 

 L 0H 



-> a-glycerophosphate 



rOH 

 ■OH 



L 0P 



Two Thioesters of 



Fatty Acid & CoA 

 [2RC0-S-CoA] 



ATP + Choline 

 4 



rFA 



Phosphatide Acid -FA 

 L 0P 



me 



Cytidine Cho 

 Triphosphate Phosphate 



->. Cytidine -diphospho' _. ., r . 

 p.hnlinp ^Diglyceride -FA 



L 0H 

 X7 



Lecithin 



Fig. 1. The Biosynthesis of Phospholipid 



rFA 

 Neutral Fat hFA 



L FA 



For choline there may be substituted ethanolamine or serine as 

 happens during the biosynthesis of phosphatides in the brain and 

 nerves by Schwann cells and probably oligodendroglial cells when 

 they are laying down myelin sheaths around axones. 



In addition to these bio-syntheses there are important catabolic 

 processes that make energy available to the cell. Fatty acids, for 

 instance, are broken down to simpler carbon products as part of a 

 process of oxidation which yields COo and water, with liberation of 



