Lactase Enzyme Lab
Exp. #1
Kathy Bui
Per. 4
DUE: 9/3/09
1
Background Info:
Lactose, the sugar found in milk, is a disaccharide composed of glucose and galactose
(both six-sided sugars). Sucrose, ordinary table sugar, is also a disaccharide composed of fructose
and glucose. Glucose is a six-sided sugar and fructose is a five-sided sugar. Lactase is an enzyme
that breaks lactose down into galactose and glucose. Sucrose is similar to lactose.
Skimmed milk is not going to remove the lactose, as the lactose is not contained
in the fat of the milk, but in the whey. Lactose intolerance is caused by some people's
inability to produce the enzyme lactase. Lactase is naturally occurring in unpasteurized
milk. Pasteurization removes the natural lactase and can make it difficult to digest any
pasteurized cheese products.
Hypothesis:
Type
A. Test tube with skim
milk and enzyme
solution.
B. Test tube with skim
milk and water.
Initial
Final
(300)
(300)
0
(mg/dl)
3000
(mg/dl)
Skim milk being a dairy product contains
a lot of lactose, but no glucose because it
is all in a disaccharide form. When adding
an enzyme solution, lactose should break
down into glucose and galactose.
0
(mg/dl)
Skim milk being a dairy product contains
a lot of lactose, but no glucose because it
is all in a disaccharide form. When adding
water, the lactose substance should not
break down because water does not
contain and enzymes (lactose).
0
(mg/dl)
Reasoning
C. Test tube with skim
milk and denatured
enzyme solution.
0
(mg/dl)
0
(mg/dl)
Skim milk being a dairy product contains
a lot of lactose, but no glucose because it
is all in a disaccharide form. An enzyme
solution is denatured when the protein
molecule loses its proper shape and cannot
function properly. In saying so, when
adding a denatured enzyme solution, the
lactose within the skim milk should not
break down.
D. Test tube with
sucrose solution and
enzyme solution.
0
(mg/dl)
3000
(mg/dl)
Because sucrose is also a disaccharide like
lactose, when an enzyme solution was
added, the disaccharides should break into
glucose and fructose.
E. Test tube with sucrose
solution and water.
0
(mg/dl)
0
(mg/dl)
Pure water contains no enzymes, in saying
so, if water is added to a sucrose solution
there should still be no presence of
glucose.
2
RAW DATA:
3
DATA:
Type
Result
Initial
(300)
Final
(300)
A. Test tube with
skim milk and
enzyme solution.
Glucose was present after
enzyme solution was added.
0
(mg/dl)
1000
(mg/dl)
B. Test tube with
skim milk and water.
No glucose was present after
water was added.
0
(mg/dl)
0
(mg/dl)
C. Test tube with
skim milk and
denatured enzyme
solution.
No glucose was present after
denatured enzyme solution was
added.
0
(mg/dl)
0
(mg/dl)
D. Test tube with
sucrose solution and
enzyme solution.
No glucose was present after
enzyme solution was added.
0
(mg/dl)
0
(mg/dl)
E. Test tube with
sucrose solution and
water.
No glucose was present after
water was added.
0
(mg/dl)
0
(mg/dl)
*Note: Trials A, B and C eventually changed into a greenish color most likely because
when milk is left out at room temperature eventually denatured itself.
Data Analysis:
Our results led us to believe that in only one of the five present trials was there
any reaction relating to the breaking of disaccharides. When an enzyme solution was
added to the skim milk, the presence of glucose changed from 0 to 1000, suggesting that
their must have been some kind of reaction even though it is not viewable by the naked
eye. When water was added to the skim milk, glucose was not recorded to be present,
suggesting that the lactose within the milk was not broken down. Also, the addition of
trial C suggests that unlike the enzyme solution, the denatured enzyme solution did not
break down the lactose in skim milk. When the enzyme solution was added to sucrose,
we also recorded no change in the number of glucose. It is expected that the last trial, trial
E, had no resulting change in the number of glucose because pure water, containing only
H20 attains no enzymes to break down any disaccharides.
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Conclusion:
In our hypothesis we stated that there is no presence of glucose because in both
cases of skim milk and sucrose, the glucose molecules are bonded with another molecule
forming a disaccharide. When adding water to these substances, there should be no
change in the molecular structure because both sucrose and skim milk are non-polar.
Also, water contains only H20 molecules, there are no enzyme substances present in pure
water hence trials B and E attains no change in the number of glucose. Denatured enzyme
solutions are enzyme solutions that have been under the influences of high temperatures,
extremes of pH, heavy metals, and alcohol. As we have learned in class, enzymes
function better at specific temperatures of pH’s. So denatured enzyme solutions will not
function properly at higher temperatures let alone at all because the molecule loses its
shape. Hence, trial C had no change in its number of glucose. Trials A and D had enzyme
solutions added to them which led us to believe that the number of glucose should grow
drastically when lactase is added to the skim milk and sucrose. Although we were correct
in saying that it would grow due to our prior knowledge of lactase’s function, the number
of glucose in skim milk did not increase drastically and the number of glucose in sucrose
did not change at all. In trial A, we forgot to take in account that skim milk is not made of
100% lactose but many other substances so the general ratio of glucose may not be that
great in the solution when the disaccharides are broken. In trial D, we did not see any
resulting increases in glucose because lactose is similar to sucrose but, lactase will break
down only lactose because of the shape of the sugar.
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Limitations
Improvements
1. Contamination: many students were using
1. Because the procedures did not clearly
the same sources so contamination may
state that contamination within this
have occurred by accidentally using the
experiment was clearly a factor, the act of
wrong droppers, etc.
2. The milk we used was left out of the
refrigerator for a period of time which
may have caused the milk to become
denatured in the process and may have
affected the experiment.
3.
contamination may have occurred and
should be added to the procedure.
2. In the procedure, a step or a note
should be added reminding future students
to place the milk back in its proper place.
In my group personally, we did not fully
3. The instructions would be helpful if
understand how the glucose test strips
changed into saying that the strips should
worked. So we had ended up making a
be dipped into the solution, taken out and
mistake when testing for glucose.
left there for 2 minutes before recording
Although the procedure instructs us to
the results of the test.
“time for two minutes and test for
1. More efficient strips or the basic strips
glucose.” we were not sure if that meant
leave the strips in the solution for two
minutes or dip the strip in and wait for two
minutes. We ended up leaving the strip in
for a long period of time.
4. The labeling system on the glucose testing
that tell you whether it is a positive (yes)
or negative (no) in regards to whether
there is or is not any glucose would have
been a much easier and more effective
process because in the group I worked
strips was also very hard to decipher. At
with, the focus was mainly directed at
one point, we all got very caught up in
what color is the strip rather than why is
fighting over what color the strip was
that strip the color that it is.
actually portraying.
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