142 CHEMISTRY OF PLANT LIFE 



ammonium hydroxide with three of its hydrogen atoms replaced 

 by methyl groups and the fourth by the ethoxyl group, the latter 

 being the ethyl group with an OH in place of one of its hydrogens. 

 Thus, 



Ammonium hydroxide Choline 



H CH 3 C 2 H 4 OH 



- 3 



H/ X)H CH 3 / X)H 



Without the choline, lecithin would be a di-f atty acid derivative 

 of glycero-phosphoric acid. These relations may be seen in the 

 following formulas: 



Fatty acid 

 HOOC-R 



C 2 H 4 \ 



>NEE(CH 3 ) 3 

 HO/ 



/fatty acid 



Or, glycerol^-fatty acid + choline = lecithin + H 2 O 



\phosphoric acid 



There are many different possible linkages of the constituent 

 groups which make up the lecithin molecule. In the first place, if 

 the (OH) groups of the glycerol molecule be numbered (1) and (2), 

 thus, 



CH 2 OH (1) 



CHOH (2) 



CH 2 OH (1) 



the fatty acid radicals may be attached either in one (1) position 

 and one (2) position, or in the two (1) positions; hence, two forms 

 of glycero-phosphoric acid are possible, thus 



/fatty acid /fatty acid 



(A) glycerol^-fatty acid (B) glycerol^-phosphoric acid 



\phosphoric acid Matty acid 



