Page 34 - exemple

Exercises

tube A only.
- Then, we place the two tubes A and B in a water bath at a temperature of 37°C for thirty
minutes.
a- Using the legends of document 1, Document 2
translate the above text into a diagram
showing the conditions of this Quantity of sucrose (ml)
experiment. 6
After 30 minutes, we measure the Tube B
5
quantity of sucrose in each of the two
tubes A and B. The measured results are 4
revealed in document 2. 3
b- Pick out from the text the tested 2
hypothesis. Tube A
1
c- Is this hypothesis validated? Justify the
Time (min)
answer based on the analysis of the
results, document 2. 0 5 10 15 20 25 30 35
d- Name the test that permits to verify the
presence of simple sugars resulting from
this digestion of sucrose.
Lebanese brevet 2008
14 Digestion of cooked starch

The adjacent document resumes the
Fresh 2 ml Gastric juice
experimental conditions of the "in vitro" saliva Cooked
digestion of cooked starch. starch
a- Describe the experiment Test
tube
schematized in this document.
b- Formulate the hypothesis tested in
A B
this experiment. A B
c- Indicate the tube where digestion of Water bath:
cooked starch occurred and explain temperature = 37°C
duration = 15 minutes
why.
Put
Lebanese brevet 2005
Add
Place

Experimental setup of the “in vitro” digestion of
cooked starch.
15 Molecular simplification of starch

Wheat starch is a complex molecule constituted of many molecules of glucose. In the course of
its digestion, starch reacts with water and is degraded into very small-sized molecules. This
chemical reaction is called hydrolysis. The enzymes, contained in saliva and pancreatic juice,
activate the hydrolytic reaction and favor the molecular simplification of starch. These enzymes
remain intact at the end of this reaction.

38