FALL, 2000

Life and change at the chemical level

Energy yielding chemical processes may occur quite slowly unless faciliated by "enzyme" catalysis. In this laboratory, different groups of students explored different aspects of these catalytic processes, including the dependence of reaction rates on enzyme and substrate concentration, temperature, and pH. The reaction investigated was the breakdown of hydrogen peroxide into water and oxygen. Oxygen evolution was measured using a Scholander respirometer.

Adria Robbin and Elizabeth Paluska

Biological Catalysts

[Experiment 1: control experiment]

Experiment 2:

What happens when you add a biological catalyst (catalase) to hydrogen peroxide?

When we did the experiment, we found that adding the catalase sped up the reaction rate of the hydrogen peroxide and caused it to produce oxygen at a higher rate than normal.

Experiment 3:

Does variation in the amount of enzyme (catalase) effect the amount of oxygen released from the hydrogen peroxide?

Hypothesis: more enzyme will increase rate of reaction.

We conclude that increasing the amount of the catalyst increases the rate of the reaction but it does not change the amount of oxygen being released.


Susy Jones and Katie Gallagher


Control: .5 ml H2O2, 4.5 Buffer

Experiment: .5 ml H2O2, 1.5 ml Catalase 3.0 ml buffer

The Question: What is the effect of adding the enzyme catalase to the hydrogen peroxide reaction?

Answer: Catalase increased the rate of reaction of hydrogen peroxide.



Experiment 1: .25 ml H2O2, 1.5 ml Catalase, 3.25 ml Buffer

Experiment 2: 1.0 ml H2O2, 1.5 ml Catalase, 2.5 ml Buffer

Question: How does the concentration of H2O2 affect the reaction in a solution of the enzyme catalase and a buffer?

Hypothesis: We predict that the greater the concentration of H2O2, the greater the amount of oxygen released in the reaction.

Procedure: We kept the amount of enzyme constant in both experiments. In our first experiment, we added .25 ml H2O2 to a solution of 1.5 ml catalase and 3.25 ml buffer. The reaction that took place produced an insignificant amount of oxygen. In our second experiment, we added 1.0 ml H2O2 to a solution of 1.5 ml catalase and 2.5 ml buffer. In this reaction, over a period of approximately nine minutes, 10 ml of oxygen was produced.

Conclusion: Both the rate of reaction and the total amount of oxygen produced increased when the amount of H202 added to the solution increased.


Shah Hossain, Joan Steiner and Sonam Tamang

1) What effect does the enzyme catalase have on the breakdown of Hydrogen Peroxide?

2) What difference did it make in placing additional amounts of enzymes/catalase? : We got no reaction when we did not include any enzymes in the first experiment. In the second experiment, which we performed twice with 3.0 ml buffer solution, 1.5ml enzyme and 0.5 ml hydrogen peroxide, we timed the reaction rate for 10 minutes recording the results every 15 seconds. For the first time we performed experiment #2, we started out with 1.4ml of oxygen and ended up with 5.2ml of oxygen after 10 minutes. For the second trial, we got

1.6 ml of oxygen and 4.8ml of oxygen after 11 minutes.

Finally, we went on to perform the third experiment. Since we were in group two, we varied the amounts of catalase to be added. For all trials, we used a constant of 0.5 ml of hydrogen peroxide.

Our results for using 0.5 ml of catalase were: 0.4ml of oxygen in the first 15 seconds and it stopped at 5.1 after 13 minutes and 45 seconds.

For using 1.0ml of catalase, we got: 0.7 ml of oxygen in the first 15 seconds and it stopped at 4.1 ml of oxygen after 11 minutes.

For our final trial with 2.0 ml of catalase, we got: 1.8 ml of oxygen in the first 15 seconds and it stopped at 4.4 ml of oxygen after 10 minutes and fifteen seconds.


Melissa Donimirski and Katie Kennedy

What is the effect of an enzyme (catalyst) on reaction rate?

First experiment, we added .5 ml of hydrogen peroxide to 4.5 ml butter. No reaction was detected.

Second experiment, we added 1.5 ml of catalase to 3 ml butter and added .5 ml of hydrogen peroxide. The amount of oxygen produced steadily increased.

Next, we set out to discover whether the amount of enzyme added changed the rate of reaction? We did this by changing the amount of enzyme added by .5 ml and keeping the peroxide at a constant .5ml.

We hypothesized that the more enzyme we added the faster the rate of reaction would be. We found this to be true, however we also found that the more enzyme we added the more oxygen the experiment would produce as well.

For instance in the first experiment using .5ml enzyme, .5ml peroxide and 4ml buffer - the first reading was .6ml and the last was 3.4ml.

In the second with 1.0ml enzyme, .5ml peroxide and 3.5ml buffer the first reading was 1.4 and the last was 3.1

Both the first and second (or rather a comparison of the two) hold up to our hypothesis.

However, the third experiment with 2.0ml enzyme, .5ml peroxide, and 2.5ml buffer the first reading was 4.2 and the last was 6.8. In this experiment the first reading was over 1ml greater than the final reading in the first and second experiments, leading us to believe that the larger amount of enzyme also yields a greater amount of oxygen.


Nimia Barrera, Meghan McCabe, and Trudell Smith


The more hydrogen peroxide is added to a solution of buffer and catalase, the faster the reaction.


Control Test Experiment

1) We mixed 1/2 ml of hydrogen peroxide and 4 and 1/2 ml of buffer. We notice no reaction in the brodie solution.

2) We proceeded to do test experiments, by adding 1 and 1/2 ml enzyme, 1/2 ml of hydrogen peroxide and 3 ml of buffer. We repeated this process twice for accuracy.



1) We test three differnt amounts of hydrogen peroxide, 0.25 ml, 0.5 ml, 0.75 ml and 1 ml.

2) We added each one to the buffer as a contant of 1.5 ml and the enzyme equal to the amount of buffer and hydrogen peroxide.

3) We measured the amount of air escaping, which determined the amount of reaction do to a 15 sec. time period.





Based on this experiment, our hypothesis is supported. The more hydrogen peroxide the faster the reaction.


Clare Lindner and Sarah Naimzadeh

Jeff mixed H202 with an unknown substance and we watched as the H202 reacted. We learned that the H2O2 was reacting with itself and the substance, an enzyme called Catalase, helped make the reaction go a bit quicker. A result of the reaction was that the H2O2 gave off O2. Our goal in the lab was to measure the amount of O2 given off which would help us measure the rate of reaction.


We added 1.5 ml of catalase and 4.5 ml of pH 7.4 buffer to the vial. As we added .5ml of H2O2, we measure the amount of O2 given off in 15 second increments. The measurements we accomplished by adding the chemicals to a closed air system. We had to keep the Brodies Solution in balance by removing O2 from the system. The control produced little or no O2 so we had no measurements.

Tests 1 &2

During these trials we reduced the amount of buffer to 3ml, which produced a lot more O2 than the control. The end of the trials we had 3.8 ml and 2.9 ml of O2.

Temperature Tests:

In the first trial we just buffer, H2O2 and Catalase that had been in a cold bath. Keeping the amount of H2O2, buffer and Catalase constant with the first and second tests and using those tests as a control, we noticed that the rate of reaction was greatly reduced. At the end of the trial we had 1.0 ml of O2 produced.

In the second trial, using the amounts constant and using the first and second trials as a control, we used H2O2, buffer and Catalase that had been heated up. We noticed that the solutions were not that hot, probably body temperature. The heat increased the rate of reaction when compared to the cold solutions, but at the end of the trial we had only 1.8 ml of O2. We expected that this would yield the most O2 of all of our trials but we were wrong.


Jakki Rowlett and Debbie Plotnick

Hypothesis: 1st experiment: catalase added to H2o2 will increase the rate of breakdown into H2O.

Experiment: control: H2O2 .5 ml; 4.5 buffer at 7.4 pH;

Result: No reaction measurable over the time allotted.

2nd experiment: 1.5ml enzyme (catalese); .5 ml H2O2; 3 ml buffer (7.4 pH)

Experiment run twice average of two tests at end 5.75cc of pressure and 4.12cc at end of time period.

3rd and 4th experiment: testing the effect of changing pH to 10.4 and 4.0 respectively

Results: virtually no change in time between control (experiments 1 & 2) and pH 10.4 Catalase works almost as well at ph of 10.4

But pH 4.0 slowed the reaction significantly.

However all except experiment with no enzyme the total volume at the end of time period was approx. the same.


Srabonti Ali and Jabeen Obaray

Hypothesis: Altering chemical environment around the enzyme will affect 3D structure.


Step 1: Mix enzyme (1.5 cc) and buffer (3 cc)

Step 2: Measure 0.5 cc of hydrogen peroxide (H2O2) squirt it into the vial

Step 3: plug the scholander respirometer

Step 4: pull plunger of syringe up or down so that Brodies solution is equal on both sides.

For our first trial experiment we used PH 7.4 as a buffer solution and we then used it as a control for our second and third experiments in which we used PH 10.4 and PH 4 as a buffer solution.


We found that the lowest PH is the slowest reaction and has the highest hydrogen ion concentration, PH 10.4 had the same reaction as the control (PH7.4) Catalat works well will more basic PH over 10. PH4 has a high hydrogen ion concentration and begins to denature the enzyme. This is what we expected.


Julie Kwon, Naomi Lim, and Mary Rochelle

Biology 103

Wesnesday Lab #4


How do changes in variables, such as the amount of substrate, enzyme, and pH, and variances in temperature affect the reaction rate of the substrate (hydrogen peroxide) and enzyme (catalase)?


1. We measured the varying amounts of enzymes.

2. We then mixed the enzyme and buffer in the vial.

3. We measured the hydrogen peroxide in the syringe.

4. Making sure that the plug was unplugged, we put the vial on.

5. We then inserted the syringe and squirted the hydrogen peroxide in first, and plunged.



Our results agreed with our hypothesis that an increase in reaction rate would result with an increase in enzyme concentration. However, there was no increase in oxygen because the substrate was held constant.


Jeanne Braha and Jessica Hayes-Conroy

Hypothesis: The rate of reaction will increase as the concentration of substrate increases.


We ran 4 trials in the Scholander respirometer with the following amounts of solutions (all in mL)

trial numberH2O2catalasebuffer (pH 7.4)

Trial #2 was done as part of our practice runs. The other practice run was a control, with no catalase. The reaction was too slow to show any oxygen production for the 360 seconds of the experiment.

Data from all four trials are shown in the accompanying chart and graph. Trial #4 did not last 360 seconds because we had to stop when 10 mL of oxygen were produced because there was no more room in the syringe.

How it worked:

We started with a system in the Scholander respirometer with equal pressure on either side of the Brodie solution. By keeping the pressures equal (seen by a level "v" of Brodie solution) we could measure the amount of oxygen produced by the breakdown of hydrogen peroxide in the presence of the enzyme catalase in the syringe. We opened the syringe to allow the escaping oxygen to have room to move without displacing the Brodie solution.

As the concentration of the substrate increased, we had to decrease the amount of buffer solution to keep total liquid volume constant so that volume would not be a variable.

We thought the reaction rate would increase with an increase in hydrogen peroxide concentration because water and oxygen, the products of the reaction are a more probable assembly than H2O2. With the enzyme, the production of oxygen and water is enhanced to speeds that are observable in a reasonable amount of time. If there are more H2O2 molecules in the same amount of total liquid and the same amount of catalase is in there, it is more likely that the H2O2, in its random movement about the vial, will bump into some catalase. When it bumps into catalase, the bonds are broken more rapidly than normal and we can see oxygen given off in the form of bubbles.

Our results strongly supported our hypothesis.