VI] THE FATS AND LIPASES 85 



There is little doubt that lipase catalyzes the synthesis of fats as 

 well as the hydrolysis ; the reaction, in fact, has been carried out to a 

 certain extent in vitro. 



Expt. 87. Demonstration of the existence of lipase in ungerminated Ricinus seeds. 



A. Remove the testas from about two dozen Ricinus seeds and pound the kernels 

 up in a mortar. Into three small flasks (a), (b) and (c), put the following : 



(a) 2 gms. of pounded seed + 10 c.c. of water. 



(6) 2 gms. of pounded seed + 10 c.c. of water + 2 c.c. of N/10 acetic acid. 



(c) 2 gms. of pounded seed + 10 c.c. of water + 2 c.c. of N/10 acetic acid, and 

 boil well. 



Add a few drops of chloroform to all three flasks, plug them with cotton-wool, 

 and allow them to incubate for 12 hours at 37° C. Then add 2 c.c. of N/10 acetic 

 acid to flask (a), and 25 c.c. of alcohol to all three flasks. Titrate the fatty acids 

 present with N/10 alkali, using phenolphthalein as an indicator. A greater amount 

 of fat should be hydrolyzed in {b) than in (a), and also slightly more in {a) than in 

 (c). The addition of alcohol checks the hydrolytic dissociation of the soap formed on 

 titration. 



B. Pound up about 15 gms. of Ricinus seeds which have been freed from their 

 testas, and let the pounded mass stand with ether for 12 hrs. Then filter, wash with 

 ether and dry the residue. Weigh out three lots, of 2 gms. each, of the fat-free meal 

 and treat as follows : 



(a) Grind up the 2 gms. of meal in a mortar with 16 c.c. of N/10 acetic acid 

 (i.e. 8 c.c. of acid to 1 gm. of meal), and let it stand for about 15 minutes. Then 

 wash well with water to free from acid, and transfer the residue to a small flask. 

 Add 5 c.c. of castor oil, 2 c.c. of water and a few drops of chloroform. 



{h) Treat the 2 gms. of meal as in (a), but, after washing, and before transferring 

 to the flask, boil well with a little distilled water. Add 5 c.c. of oil, 2 c.c. of water 

 and a few drops of chloroform. 



(c) Put the 2 gms. of meal into the flask without treatment and then add 5 c.c. 

 of oil, 2 c.c. of water and a few drops of chloroform. 



Incubate all three flasks for 12 hours, and then titrate with N/10 caustic soda, 

 after addition of alcohol as in ^. A certain amount of acetic acid is always retained 

 by the seed residue, and this is ascertained from the value for flask {l>). Flask (c) 

 will act as the control. 



Another question to be considered is the mode of synthesis in the 

 plant of the complex fatty acids which form the components of the fats. 

 No conclusive work has been done in this direction, but many investi- 

 gators have held the view that the fats arise from carbohydrates, notably 

 the sugars. In fact, it has been shown that in Paeonia and Ricinus, as 

 the seeds mature, carbohydrates disappear and fats are formed. 



The sequence of events, however, in the synthesis of fatty acids 



from sugars is very obscure. If we examine the formulae, respectively, 



of a hexose : 



CH.,OH -CHOH-CHOH • CHOH ■ CHOH • CHO 



