Aim
In this investigation my aim is to find out how the concentration of
enzyme (amylase) will affect the rate of reaction.
Prediction
I predict that the higher the concentration of enzyme the faster the
reaction will occur. This because there will be more active sites,
therefore more possible collisions which will result in starch being
broken down into maltose.
Method
1. Set up equipment as shown in diagram
2. Put 2 drops of iodine into each dimple of both the trays.
3. Heat the 0.25% concentration of Amylase for 3 minutes in a
hot water bath set to 37’C.
4. After add 3ml of the heated Amylase to 3ml of starch.
5. Mix using pipette.
6. Set timer
7. Add a drop of mixture to each dimple full of iodine every 30
seconds until colour of the mixture changes.
8. Now record amount of time taken in table.
9. Repeat all these steps for each concentration of Amylase.
Fair test
In this investigation I will change the concentration of amylase, I will
keep the amount of Amylase, starch, iodine, and temperature and
time in water bat the same. And I will measure the time taken fort
he reaction to happen. This will ensure that the investigation is a fair
test.
Safety
To ensure that this investigation is safe I will wear goggles as iodine
can be an irritant. A cloth will be kept to clean up any spillages and
hair will be tied back to ensure that it doesn’t get in the way.
Equipment list
For this investigation I will require,
1. Amylase at 0.25%, 0.50%, 0.75%, 1.00% and also 1.25%
concentrations.
2. 2 Dimple trays
3. 7 pipettes
4. Beaker of Iodine.
5. Beaker of Starch.
6. Water bath set at 37 C
7. Timer
8. Measuring Cylinders
Results
Amylase
Test Number (seconds)
%
1
2
3
4
5
6
7
Average
Rate= Starch Digested/Time
Taken
0.25
360
570
460
1200
180
720
356
549
0.005
0.5
330
390
275
540
120
510
325
356
0.008
0.75
270
360
195
165
60
330
272
236
0.013
1
250
310
180
120
30
60
248
171
0.018
1.25
150
250
170
60
15
20
220
126
0.024
Rate calculation based on 3mg as initial starch solution.
‘Average’ was calculated as a mean of values form tests 1-7 for each
amylase concentration.
‘Rate’ was based on the average using the formula
Starch Digested / Time Taken To Digest= Rate mg/sec
Conclusion
In the results we can definitely see that as the concentration of
Amylase is increased the rate also increases. This is because as the
concentration of Amylase increases the number of active sites for
reaction to occur will also increase meaning that more collisions
could occur every second therefore allowing the starch to be
digested faster. We can also see through the graph that the speed is
not exactly doubled as the concentration is doubled this may be
because of wasted collisions between the enzyme and the substrate.
In a wasted collision the substrate does not join to the enzyme as it
does not hi the active site fully this means that the collision does not
result in a reaction therefore no starch is digested into maltose. I can
see that my prediction was partly correct as I had stated that as the
concentration was increased the rate would also increase. But the
results did not double as the concentration was doubled as I had
stated but this may be down to other factors that we had not
accounted for.
Evaluation
In this investigation I can see that there are certain inaccuracies in
my results. This may not just be down to my own fault but also
factors beyond my control. As this was an experiment conducted in
school the class was split into 7 groups that each completed the
experiment by themselves. This resulted in more results for a better
average but as each group completed the investigation by themselves
the stopping of the timer became subjective based on an individuals
perception as to when the iodine had changed completely showing
there was no starch left and based on various individual’s decisions as
when to take the reading. This reduces the reliability of the results.
Quantifying the readings would remove this problem. There were
many factors in this experiment that were not kept constant
throughout. The temperature of the room would have varied
throughout the experiment therefore giving the molecules more
kinetic energy resulting in more collisions. Another factor that can
affect the rate could be contamination in the equipment used and
also contamination or variation in the starch and iodine. Factors such
a different batches of iodine could mean that the colour change
would be different therefore all the groups would have different
readings which would decrease the accuracy of the results.
Contamination could affect how the enzyme would work and could
also affect the concentration giving less reliable results. As previously
mentioned the fact that it was persons own opinion as to when the
iodine had changed colour enough would have affected the results.
This could be changed with the use of a colorimeter which would
could have been used to give precise results about when to stop the
time as the colour had changed sufficiently. Although this would
dramatically increase accuracy it would take much longer and would
not be a viable option in a school environment where the time
allowed it restricted. Furthermore we could also increase accuracy by
using more accurate pipettes which were not available to us in
school. These pipettes can be set to drop a certain amount of liquid
every time, this would mean that all measurement were correct
therefore the rate would be more accurate. Lastly to increase
accuracy we could also have used more concentrations these results
would give us a better and also more accurate graph.
Further Investigations
Another experiment that could be carried out would be the using a
different enzyme and a different method. Such a practical could be
that using catalyse. In this experiment liver containing catalyse could
be used. Every cell produces metabolic waste or Hydrogen peroxide
(2H202) catalyse in the liver breaks this down therefore changing the
concentration of Hydrogen peroxide should change the rate at
which the Hydrogen is broken down. This equation shows the
reaction 2H202 O2+H2O this shows us that the Hydrogen peroxide
is broken down into water and oxygen and this oxygen could be
used to measure the rate of the reaction. The experiment could be
carried out using this method.
Method
1. Set up equipment as in diagram.
2.
3. Set timer for 3minutes and place a measured amount of liver in
the beaker and start time.
4. After the time has finished remove the delivery tube from the
tub leaving just the measuring cylinder and then measure the
amount of oxygen produced. Record this in a table.
5. Repeat this for concentration 0.25%, 0.50%, 0.75, 1.00%,
1.25%.
6. Record these results repeat practical under same conditions 3X.
7. Work out averages and rate of reaction and draw graph.
This method would produce accurate results as nothing is subjective
to a person’s opinion and also as the experiment is repeated 3 times
under the same conditions the results would be quite accurate. An
alteration that could be made is that instead of liver, catalyse could
be by itself which would give a more accurate results because the
weight could be altered due to density or even water content.
