BSCS: Energy, Life and the Biosphere Name:___________________________
Proof of Enzyme Action Lab
Enzymes are specific proteins that exist in all living things. These proteins
speed up chemical reactions by reducing the amount of ________________
_____________ required for the chemical reaction to take place.
The chemical reactions we have been discussing mostly in class have been
___________________ reactions. One common decomposition reaction is
the breaking of starch into smaller molecules, to release the energy stored
in the chemical bonds.
Starch is a _____________________, made up of many molecules of
_________________ (a monosaccharide) joined in a long chain. Although
the chemical bonds of starch hold immense amounts of energy, starch cannot
be easily broken down. Our bodies do not have the high amounts of
____________ ____________ required to undergo such an ominous task!
Thankfully, though, we have _____________. If the proper enzyme is
added to starch, it will greatly speed up the chemical reaction of breaking
starch down into glucose. Think of all the energy that is to be had!
Amylase is an ____________ which can be added to starch to break it down
into _____________.
Procedure: Please follow along and answer all questions carefully as you go.
Part A: Starch Model Information
Examine the following sketch.
It represents a model of a starch molecule. Note that a starch molecule is
made of _____________ molecules attached together.
BSCS: Energy, Life and the Biosphere Name:___________________________
Describe the appearance of a starch molecule:
_________________________________________________________
_________________________________________________________
Do you see any glucose molecules that are NOT attached to the chain?____
If you were to test for the presence of free glucose molecules when using
starch, might you be able to detect any free glucose at this time?________
Part B: Testing for Starch and Glucose in the Starch Solution
1. Using Iodine to test for starch: In one test tube, put 20 drops of starch
and 1 drop of iodine.
The following color changes are indicators of the presence/absence of
starch:
Deep blue indicates that a lot of starch is present
Light blue indicates that a little starch is present
No blue color indicates the absence of starch, possibly the presence of
glucose
2. Using Benedicts Solution to test for glucose: In the other test tube, put
20 drops of starch and 20 drops of Benedicts Solution.
4. Heat ONLY the test tube with starch and Benedict's Solution in the
hot water for 2 minutes.
After heating, the following color changes are indicators of the
presence/absence of glucose:
Bright blue indicates that there is no glucose present, it is just starch
Green, yellow, orange or red tells you that glucose is present.
5. After 2 minutes, record the color of the solutions in BOTH tubes in the
"Starch Only" section of the following Data Chart:
Testing Chemical Starch Only
Iodine
Benedict's solution
BSCS: Energy, Life and the Biosphere Name:___________________________
What do these test results indicate as to the presence or absence of starch
in each test tube?
_________________________________________________________
_________________________________________________________
_________________________________________________________
What do the test results tell you about the possible presence of glucose in
each test tube?
_________________________________________________________
_________________________________________________________
_________________________________________________________
Are your test results in agreement with the sketch on Part A? __________
Part C: Enzyme Model Information
Examine Figure 12-4.
It represents the shape of 3 different enzymes.
One of these models shows the appearance of the enzyme known as amylase.
Amylase is __________ whose function is to break _________ into
____________.
Whichever enzyme is amylase will attach perfectly to the starch substrate,
and "break off" glucose molecules from the starch molecules.
BSCS: Energy, Life and the Biosphere Name:___________________________
The amylase model in figure 12-4 will fit exactly into the places where the
glucose molecules are attached to form starch. This site is shown with two
arrows in figure 12-5.
Which model (A, B, or C) will best fit the glucose molecules joined together
in the starch molecule? __________
On Figure 12-5, draw in the best fitting enzyme.
Part D: Starch Model and Enzyme Model Action
What is the role of amylase?___________________________________
________________________________________________________
Use figures 12-5 and 12-6 to explain how the enzyme does its job.________
_________________________________________________________
_________________________________________________________
_________________________________________________________
What new molecule appears in figure 12-6 that was not present by itself
before? ____________________
Where did this new molecule come from?_________________________
Part E: Testing the Results When Starch is Mixed with Amylase Enzyme
1. Clean out your test tubes.
2. Put 20 drops of amylase and 20 drops of starch into EACH test tube.
3. Gently swirl each test tube.
4. Let stand for 5 minutes (yes- you need to wait the entire 5 minutes!)
5. After 5 minutes, add 20 drops of Benedict's solution to one test tube
and place it into the boiling water bath to test if the starch has been
broken down into glucose.
BSCS: Energy, Life and the Biosphere Name:___________________________
After heating, the following color changes are indicators of the
presence/absence of glucose:
Bright blue indicates that starch is present, but no glucose
Green, yellow, orange or red tells you that glucose is present.
6. Put 1 drop of iodine into the other test tube to test if there is still
starch in the test tube. This test tube DOES NOT go into the boiling
water bath.
The following color changes are indicators of the presence/absence of
starch:
Deep blue indicates that a lot of starch is present
Light blue indicates that a little starch is present
No blue color indicates the absence of starch and the possible presence of
glucose
Record the color of the solutions in BOTH tubes in the "Starch With the
Amylase Enzyme Added" section of the following Data Chart:
Testing Chemical Starch With the Amylase Enzyme
Added
Iodine
Benedict's solution
What do these test results indicate as to the presence or absence of starch
in each test tube?
_________________________________________________________
_________________________________________________________
_________________________________________________________
What do the test results tell you about the possible presence of glucose in
each test tube?
_________________________________________________________
_________________________________________________________
_________________________________________________________
BSCS: Energy, Life and the Biosphere Name:___________________________
Analysis
1. Define these terms:
a. Enzyme: _______________________________________________
b. Starch: _______________________________________________
c. Glucose: _______________________________________________
d. Amylase: _______________________________________________
2. a. In Part B, was starch present in the test tubes? ______________
b. What was your evidence based on the iodine test? ______________
_________________________________________________________
c. What was your evidence based on the Benedict's test? ______________
_________________________________________________________
3. a. In Part E, was starch present in the test tubes? ______________
b. What was your evidence based on the iodine test? ______________
_________________________________________________________
c. In Part E, was glucose present in the test tubes? ______________
d. What was your evidence based on the Benedicts test? ______________
_________________________________________________________
e. What was added to the tube of starch that made the change?
_________________________________________________________
f. What molecule was now present in the tube with Benedict's solution, that
was not present before? _____________________________________
g. Where did this molecule come from? ______________
_________________________________________________________
4. a. A substance upon which an enzyme acts is called a substrate. What was
the substrate in this experiment? ____________________________
b. What was the enzyme used in this experiment? ___________________
