EXERCISE 57 



Problem. What physical changes result from the digestion 

 of starch ? 



What to use. Four "artificial root hairs" made as described 

 in Exercise 4 1 ; boiled starch paste, thin enough to pour easily ; 

 diastase 1 ; pancreatin ; saliva (see note I, Exercise 56); iodin 

 solution ; Fehling solution. 



What to do. Fill the celloidin membranes with starch paste. 

 Into one mix a small amount of diastase; into the second, some 

 pancreatin ; into the third, about a teaspoonful of saliva. Im- 

 merse each sac in water, as shown in diagram. Test the water surrounding each cell for starch and 

 for reducing sugar. Record results. After twenty-four hours test again and record. Then test contents 

 of each sac for starch and for sugar. Complete record in table. 

 Record. 



Conclusions. What is the answer to the problem ? 



Questions. 1. Can starch diffuse through a cell wall ? 



2. Can sugar diffuse through a cell wall ? 



3. What is the source of any sugar found in this experiment ? 



4. What can change starch into sugar ? 



5. Will starch change into sugar of itself ? 



6. How does digested starch differ from undigested starch ? 



1 The diastase should be tested before used, as the commercial product sometimes contains a reducing sugar. 



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