Enzyme Experiment
Purpose:
The purpose of this experiment is to find out by changing the substrate concentration will
affect the rate of enzymes.
Hypothesis:
1. What is the optimum pH for potato?
The optimum pH level for potatoes is 5-6.
2. What is the reasonable temperature for potato ?
The reasonable temperature for potatoes should be around 37 degree Celsius.
3. By adding more enzyme, will the reaction be faster?
I think by adding more enzymes to the solution the reaction will be much faster. Since
enzyme is a protein that speeds up or slow down a reaction.
4. If you increase substrate concentration will the rate of enzyme action increase forever?
I think if we increase the substrate concentration the rate of enzyme will be faster, but there
will be a point where the enzyme will be saturated. It also increases the chance for
substance to bind with the active site of the enzyme.
Equipment List:
1. 4 potatoes
2. 200 mL of water for blending potato
3. Blender
4. Funnel
5. Filter paper
6. 15 equally-sized paper disks
7. Hole puncher
8. small knife
9. H2O2
10. small spoon
11. measuring cylinder
12. beakers
13. Water for mixing with H2O2
14. tweezers
15. timer
16. lab coat
17. safety goggles
18. 500 mL
Procedure:
1.
2.
3.
4.
5.
Slice 4 potatoes into smaller pieces using a small knife.
Fill 200 mL of water in a beaker and pour it in the blender.
Put the potato pieces into the blender and then blend it.
Pour around 200 mL of potato juice into a beaker.
Put the funnel on a smaller beaker or a measuring cylinder with filter paper around it
and pour the potato juice in.
6. Slowly stir the potato juice with a small spoon to filter the potato juice and isolate
the enzyme (catalase).
7. Continue until you get 10 mL of filtrates in the smaller beaker/ measuring cylinder.
8. Use the hole puncher to get 15 equally-sized pieces of paper disks from filter paper.
9. Prepare 4 beakers and label each of them with a specific substrate concentration
(0%, 3.75%, 7.5%, 15%, and 30%)
19. Prepare the 30% substrate concentration by adding 40 mL of H2O2into the beaker
20. Pour 20 mL of the H2O2into the 15% substrate concentration beaker from the 30%
substrate concentration beaker, and add 20 mL of water to it
21. Pour 20 mL of the solutioninto the 7.5% substrate concentration beaker from the 15%
substrate concentration beaker, and add 20 mL of water to it
22. Pour 20 mL of the solutioninto the 3.75% substrate concentration beaker from the
7.5% substrate concentration beaker, and add 20 mL of water to it
23. Pour 20 mL of water into the 0% substrate concentration beaker
10. Place a paper disk in the potato filtrates with catalase for 10 seconds, and then take
it out.
11. Use the tweezers to place the paper disk at the bottom of the 30% substrate
concentration beaker.
12. Record the time it takes for the paper disk to float up.
13. Repeat steps 10-12 with 2 other paper disks in the same beaker and then average
the results
14. Repeat steps 10-13 but experiment it on other concentrations with a specific
substrate concentration (15%, 7.5%, 3.75%. and 0%)
Results:
Substrate
0%
3.75%
7.5%
15%
30%
Concentration
(moles)
Trial 1 (seconds)
Trial 2(seconds)
Trial 3(seconds)
Average time
(seconds)
∞
∞
∞
∞
17.8
14.9
15.4
16.033
7.59
10.39
9
8.993
5.5
4.0
6.6
5.367
4
3.6
3
3.533
Analysis:
Equipments
200 mL beaker
Graduated cylinder
Timer
Uncertainties
+-5 % (+-10mL)
+- 0.5%
+- 5 seconds
By looking at my error bars the human error for time (y axis) is only 0.03 seconds.
We are humans and we cannot stop the timer at that exact time. There will be a few
seconds of delay. But when we are measuring the amount of substrate concentration we
can make a lot of human errors. The reason why we have human errors is because
sometimes when we are measuring a liquid substance we might not be looking at the
bottom of the meniscus. We can improve by making sure the beaker is on a flat surface
while we are measuring. And we can also make sure that we are looking at the bottom of
the meniscus while measuring.
The equipments also have uncertainties. The uncertainties of the equipments and
human error together show us how much errors we made during the experiment. We can
improve by paying more attention to what we are doing to avoid as much human errors as
possible. Also, we can reduce the amount of human errors by measuring small amounts at
each time.
When we are doing the experiment, quite a few people got burned by the hydrogen
peroxide. This is because we weren’t careful while pouring and measuring the hydrogen
peroxide. Next time, we can pay more attention while pouring and measuring hydrogen
peroxide to prevent burns. We also wasted a lot of time on waiting for each other to finish.
We can prevent this from happening by making sure everyone in the group is doing
something. Whoever finishes the measurements will start with the experiment instead of
waiting for each other to finish and start together.
The error bars tells us that our results are not a 100% correct. The error bars tells us
that our results might be plus or minus the amount shown on the error bars for both our x
and y axis.
When we measured water and hydrogen peroxide we used different beakers to
measure them. When we pour them into another beaker there will be some water left
behind on the beaker because of cohesion and adhesion. I had some difficulties measuring
the hydrogen peroxide so I kept pouring it back to the bottle and out again. There will be
some hydrogen peroxide left behind to because of hydrogen peroxide. When we put the
filter paper with catalase on the bottom of the beaker. We didn’t exactly start the timer on
the dot because we are humans and our fingers can’t be accurate there is a delay in time.
Conclusion:
By look at the graph the higher the percentage of the hydrogen peroxide the lower
the time the filter paper needs to come to the top of the beaker. This proves that if we
increase the substrate concentration the rate of the enzyme will be faster. In the beaker
that has 30% of hydrogen peroxide has the fastest rate of enzyme. We can also tell by
looking at the graph that there is a curve line and the time is decreasing as the increase of
the substrate gets higher. Of Course, the beaker with 0% substrate concentration in it is
infinity. It is infinity because there is no enzyme for it to speed or slow down the reaction.
There is no reaction going on in the 0% beaker.
My hypothesis is correct for the substrate concentration one because by looking at
the results, the time it took for the filter paper decreased, which means the reactions of
enzymes happened faster. The enzyme is the catalase, which is filter out from the potato
juice and the substrate is the hydrogen peroxide. Catalase reacts with the hydrogen
peroxide which binds to the active site of the catalase. The hydrogen peroxide needs to be
broken down so that there is a reaction happening. The hydrogen peroxide is chemically
decomposed into two parts water (h20) and oxygen (02). The reason the filter paper is able
to flow up from the bottom of the beaker because oxygen is created. As we increase the
concentration solution more hydrogen peroxide is able to bind with the enzyme’s active site
and it decreases the time it takes for oxygen to be produced and allowing the filter paper to
flow up.
The line on the graph is an exponential line which means as we increase the
substrate concentration the time decreases exponentially, the rate of the enzymes are
increasing exponentially. We also test the filter paper with catalase on it will not float up
from the bottom if the beaker only contains water and no hydrogen peroxide. The is no
reaction happening because there is no substrate for the catalase to react with, which
results to no oxygen produced in order for the filter paper to float up. That’s why our time
for the 0% is infinite because it is more than 15 minutes. The filter paper may come up but it
takes a huge amount of time. By look at the graph, the 3.75-7.5% substrate concentration,
the time it takes for the filter paper to float up is very fast. This is because there are
hydrogen peroxide molecules for the catalase to react with, so the rate of the enzyme
increases too. From 7.5-15% the rate of decreasing begins to slow down because as the
amount of substrate concentration increase the enzymes stay the same. But from 15-30%
substrate concentration the decreasing becomes very slow. This is because there are a lot of
substrates but not enough enzymes to react with all of them at the same time.
The law of collision is one way to describe this experiment. Enzymes are said to work
and carry their functions out when they collide with chemicals. Just like how enzymes carry
out their functions with the presence of hydrogen peroxide. I have learned from this
experiment that when we increase the substrate concentration the rate of the enzyme’s
reaction gets faster. It gets faster because there are a lot of hydrogen peroxide molecules
for the catalase to react with, so the rate of the enzymes increases too.