1 92 PHYSIOLOGICAL CHEMISTRY 



do you find the most satisfactory digestion? How do the results compare with 

 those obtained from the similar series under Trypsin, page 190? 



2. The Most Favorable Temperature. (For this and the following series of 

 experiments upon pancreatic amylase use the neutral extract plus an equal vol- 

 ume of 0.5 per cent sodium carbonate.) In each of four tubes place 2-3 c.c. of 

 alkaline pancreatic extract. Immerse one tube in cold water from the faucet, 

 keep a second at room temperature, and place a third on the water-bath at 4OC. 

 Boil the contents of the fourth for a few moments, then cool and also keep it at 

 4OC. Into each tube introduce 2-3 c.c. of starch paste and note the progress of 

 digestion. At the end of one -half hour divide the contents of each tube into two 

 parts and test one part by the iodine test and the other part by Fehling's test. 

 In which tube do you find the most satisfactory digestion? How does this result 

 compare with the result obtained in the similar series of experiments under 

 Trypsin (see page 190)? 



3. Influence of Bile. Prepare three tubes as follows : 



(a) 2-3 c.c. of pancreatic extract+2-3 c.c. of starch paste + 1/2-1 c.c. of 

 bile. 



(b) 2-3 c.c. of pancreatic extract+2-3 c.c. of starch paste +5 c.c. of bile. 



(c) 2-3 c.c. of pancreatic extract+2-3 c.c. of starch paste. 



Shake the tubes thoroughly and place them in the incubator or water-bath 

 at 4OC. Note the progress of digestion frequently and at the end of a half-hour 

 divide the contents of each tube into two parts and test one part by the iodine 

 test and the other part by Fehling's test. What are your conclusions regarding 

 the influence of bile upon the action of pancreatic amylase? 



4. Digestion of Dry Starch. To a little dry starch in a test-tube add about 

 5 c.c. of pancreatic extract and place the tube in the incubator or water-bath at 

 40C. At the end of a half-hour filter and test separate portions of the filtrate 

 by the iodine and Fehling tests. What do you conclude regarding the action of 

 pancreatic amylase upon dry starch? Compare this result with that obtained in 

 the similar experiment under Salivary Digestion (page 60). 



5. Digestion of Inulin. To 5 c.c. of inulin solution in a test-tube add 10 drops 

 of pancreatic extract and place the tube in the incubator or water-bath at 4oC. 

 After one-half hour test the solution by Fehling's test. 1 Is any reducing substance 

 present? What do you conclude regarding the digestion of inulin by pancreatic 

 amylase? 



6. Quantitative Determination of Amylolytic Activity. Wohlgemuth's 

 Method. 2 Arrange a series of test-tubes with diminishing quantities of the 

 enzyme solution under examination, introduce into each tube 5 c.c. of i per cent 

 solution of soluble starch 3 and place each tube at once in a bath of ice-water. 4 



1 If the inulin solution gives a reduction before being acted upon by the pancreatic juice 

 it will be necessary to determine the extent of the original reduction by means of a "check" 

 test (see p. 47). 



2 Wohlgemuth : Biochemische Zeitschrift, 9, i, 1908. 



3 Kahlbaum's soluble starch is satisfactory. In preparing the i per cent solution, the 

 weighed starch powder should be dissolved in cold distilled water in a casserole and stirred 

 until a homogeneous suspension is obtained. The mixture should then be heated, with con- 

 stant stirring, until it is clear. This ordinarily takes about 8-10 minutes. A slightly opaque 

 solution is thus obtained which should be cooled and made up to the proper volume before 

 using. 



4 Ordinarily a series of six tubes is satisfactory, the volumes of the enzyme solution used 

 ranging from i c.c. to o.i c.c. and the measurements being made by means of a i c.c. gradu- 

 ated pipette. Each tube should be placed in the ice-water bath as soon as the starch solu- 

 tion is introduced. It will be found convenient to use a small wire basket to hold the tubes. 



