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Exercises

8 Convenient medium for the enzymatic activity

We perform an in vitro digestion of cooked starch in three test tubes A, B and C. The conditions
and the results of the experiment are summarized in the following table:

Tube Content of the tube at the Test performed half an hour later
beginning the experiment Iodine water Fehling solution

A 20 ml of cooked starch + saliva Brown orange Brick red precipitate
coloration
B 20 ml of cooked starch + saliva
Blue coloration Negative test
+ few drops of acid
C 20 ml of cooked starch + saliva
Blue coloration Negative test
+ few drops of base

a- Why did we add saliva to the three test tubes?
b- Formulate the tested hypothesis in this experiment.
c- Do the obtained results validate the formulated hypothesis? Justify the answer.

9 Convenient conditions for digestion

Place for one hour six test tubes A, B, C, D, E and F in the experimental conditions resumed in
the following table:

Tube Food Chemical Enzyme Temperature Time
medium

A Butter Basic Lipase 37ºC 1 hour

B Butter Basic Lipase 37ºC 10 minutes

C Butter Acid Lipase 37ºC 1 hour

D Albumin Basic Lipase 37ºC 1 hour

E Albumin Acid Pepsin 37ºC 1 hour

F Albumin Acid Pepsin 60ºC 1 hour

a- In which test tubes digestion occurred? Justify the answer.
b- Indicate the reason behind the absence of digestion in the other tubes.

Digestion 35