at 20 C. Record your results in the form of a table. How near 

 in agreement are the two determinations at 20 C. ? \Yhat is the 

 increase in rate of enzyme action for a rise of 20 C.? 



IC2. Rate of decomposition of H. 2 O. 2 by catalase at different' 

 temperatures. Place 25 cc. of dilute filtrate from crushed liver 

 suspension in a bottle provided with a perforated cork and bent 

 or flexible tube ; place carefully in the bottle, witJiout spilling, a small 

 vial with 5 cc. H.,( )., solution. Insert the end of the bent tube below 

 the mouth of a eudiometer or inverted graduate filled with water 

 and placed mouth downward in a beaker of water. Then shake 

 the bottle so as to spill the vial and mix its contents with the liver 

 extract. Measure the volume of O. 2 evolved from minute to 

 minute and record the results. Try the experiment with ( a ) cold 

 mixture (liver-extract ami HoO, cooled just before mixing to 

 about o C. ), (b) mixture at room temperature (20 ), and (c) at 

 40. Estimate the relative rates of action at the different tem- 

 peratures. 



103. Effect of concentration of enzyme on enzyme action. 

 (Quantitative determination. ) 



Collect saliva and filter. Add 5 cc. dilute starch paste to each of 

 two test tubes. 



Have a series of iodine drops ready on a porcelain plate as in exp. 

 101. Add as follows to the two test-tubes: 



a. 5 cc. of r pt. saliva to 3 pts. water. 



b. 5 cc. of i pt. saliva to / pts. water. 



Keep at 20 C and determine by trials at one-minute intervals when 

 the iodine gives no color reaction with the mixture. 



After making the first series of experiments perform the same 

 experiments using the same saliva diluted as follows : 



c. 5 cc. starch paste -|- 5 cc. of i pt. saliva to 15 pts. H. 2 O. 



d. 5 cc. starch paste + 5 cc - ot ~ l pt- saliva to 31 pts. H 2 O. 

 Keep at 20 C. and determine by trials at two-minute intervals the 



time required to convert the starch to a substance giving no color 

 with iodine. 



E. ENZYMES AND METABOLISM IN CELLS. 



In living cells syntheses, hydrolyses, and oxidations, all of which 

 are under the influence of enzymes, interact in the metabolic pro- 

 cesses. The interdependence of syntheses and oxidations is well 

 shown in Pasteur's experiment. The metabolism of the cell varies 

 according to the quantity of oxygen available. 



27 



