- In this experiment you will observe the action of the enzyme amylase on starch. Amylase changes starch into a simpler form: the sugar maltose, which is soluble in water. Amylase is present in our saliva, and begins to act on the starch in our food while still in the mouth.
- Exposure to heat or extreme pH (acid or base) will denature proteins. Enzymes, including amylase, are proteins. If denatured, an enzyme can no longer act as a catalyst for the reaction.
- Benedict's solution is a test reagent that reacts positively with simple reducing sugars like maltose, but will not react with starch. A positive test is observed as the formation of a brownish-red cuprous oxide precipitate. A weaker positive test will be yellow to orange.
MATERIALS:
Cornstarch
Distilled water
Saliva
Vinegar
Benedict's qualitative solution
3 graduated cylinders (10mL)
250-ml beaker
Stirring rod
3 test tubes (16 x 125mm)
Test tube rack
Wax pencil
Hot platePRE-LAB:
- Add 1g of cornstarch to a beaker containing 100ml of cold distilled water. While stirring frequently, heat the mixture just until it begins to boil. Allow to cool.
PROCEDURE:
1. Fill the 250-mL beaker about 3/4 full of water and place on the hot plate for a boiling water bath. Keep the water JUST AT BOILING.
2. Mark 3 test tubes A, B and C. "Spit" between 1 and 2 mL of saliva into each test tube.
3. Into tube A, add 2 mL of vinegar. Into tubes B and C, add 2 mL of distilled water. Thump the tubes to mix.
4. Place tube B into the boiling water bath for 5 minutes. After the five minutes, remove from the bath, and place back into the test tube rack.
5. Add 5 mL of the starch solution to each tube and thump to mix. Allow the tubes to sit for 10 minutes, occasionally thumping the tubes to mix.
6. Add 5 mL of Benedict's solution to each tube and thump to mix. Place the tubes in the hot water bath. The reaction takes several minutes to begin.
OBSERVATIONS:
Tube A: Starch + saliva treated with vinegar (acid)
- Was the test positive or negative? _______________________
What does this indicate?________________________________________________
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Tube B: Starch + saliva and water, treated in a boiling water bath- Was the test positive or negative? _______________________
What does this indicate?________________________________________________
____________________________________________________________________
____________________________________________________________________
Tube C: Starch + saliva- Was the test positive or negative? _______________________
What does this indicate?________________________________________________
____________________________________________________________________
____________________________________________________________________
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Back to Lab Dad's Laboratory
- Exposure to heat or extreme pH (acid or base) will denature proteins. Enzymes, including amylase, are proteins. If denatured, an enzyme can no longer act as a catalyst for the reaction.
ENZYME ACTION ON STARCH
Amylase
INTRODUCTION: