The Difference Between Enzyme Reactions due to Varying pH
Zane Rusk, Alexis Stroud, Quentin Romero, Aileen Sotelo
Amarillo College and Randall High School
Introduction
Enzymes are the catalysts of biological systems.
Since decomposition reactions take a long time
to occur, the enzymes lower the activation
energy in order for the reaction to speed up. For
example, an enzyme found in the liver is called
catalase. Catalase breaks down hydrogen
peroxide into hydrogen and oxygen faster than
the normal reaction so there won’t be so much
metabolic waste. There are many factors that can
affect the function of enzymes such as
temperature, pH, a change in enzyme
concentration or a change in substrate
concentration. In our experiment, we tested to
see if different pH levels changed the reaction
rate of the enzyme. Beef catalase was our
enzyme and Hydrogen peroxide was our
substrate. Depending on how far the enzyme
was past its optimal pH, it can denature or
become non-functional from the change in
shape. Our group hypothesized that there was a
difference between reaction rates at varying pH.
Key
Data
Reaction at pH of 3
Reaction at pH of 7
Reaction at pH of 11
- Trial 1
- Trial 2
- Average rate of change
• Original function- positive curve
• Derivative- negative curve
Conclusion
Trials
Average rate of
change for pH 3(020sec)
Average rate of change for pH 7
(Atm/sec)
Average rate of change for pH 11
(Atm/sec)
Trial 1
0.013895 Atm/sec
0.015665
0.015045
Trial 2
0.016445Atm/sec
0.015705
0.017095
0.0157
0.01605
Average of 0.01515 Atm/sec
both trials
Methodology and Procedures
For our data collection, we set the LabQuest to measure the pressure of the container in atmospheres over an
interval of 60 seconds. We gathered the beef catalase and pH solution and mixed them together in the test
tube (We did this to ensure that the two were in even distribution and that we wouldn’t have to rely on
random collisions; the reaction rate would be an accurate representation of the enzyme reaction in the
selected pH environment). We poured the hydrogen peroxide into the prepared test tube and as quickly as
possible sealed it with the stopper/pressure gauge and started Data Collection on the LabQuest.
This process was repeated a total of 6 times, with 2 trials at each pH environment (we did pH 3, 7, and 11).
Later we took our collected data and imported it into Logger Pro, created a curve fit to our original data in
order to get an equation to find the derivative of. We took this curve fit derivative to get the rate of reaction
at every data point over the 60 seconds of data collected.
We also found the average rate of change over the interval 0 – 20 seconds; lines are drawn on the graph and
values are shown in the data table.
From the data in our experiment we
concluded there is a difference between the
reaction rates and the change in pH
concentration. There was evidence to
determine that the higher the pH, the more
quickly reactions were occurring. For
instance, when holding the test tube and
the plug, we found it was harder to hold
the plug in to the test tube as time
progressed in a pH environment of 7 rather
than a pH environment of 3. . We should
see some rxn rate data to substantiate this
claim. Include those #s. Feeling isn’t
quantitative!
The investigation could have been
improved with more trials to ensure
accuracy of data.
An interesting
investigation would be taking the pH
concentrations to a higher level and
determining the optimal pH for the highest
rate of reaction