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Inquiry Activity

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by

Lilian Fajardo

on 8 October 2015

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Transcript of Inquiry Activity

Inquiry Activity
pH of
hydrogen peroxide on
respiration rate
Introduction:
Enzymes are proteins that act as catalysts to speed up chemical reactions by lowering the activation energy required for the reaction to take place. Catalase is an enzyme found in most aerobic organisms that decomposes hydrogen peroxide (h2o2). At the end of their reaction the products are water and oxygen gas, the rate of this reaction is usually measured by the total oxygen gas produced over a period of time. In this experiment the influence of pH on these reactions was tested, the hypothesis was: "The higher the pH (more basic) of the solution the slower the reaction rate due to protein denaturazation."
Methods:
Gather the following materials:
20 well micro plate
forceps
stopwatch
2 30 mL medicine cups
filter paper
15 mL h2o2 with pH buffer of 6,7,8,9
5 pipettes
5 mL of 400 u/mL catalase
Procedure:
The materials are gathered, and the 20 well micro plate is labeled A1-D6. Using the pipette put 3 mL of 400 u/mL of catalase in wells A1-C1, in A2-C2 put 3 mL of 1.5% of h2o2 with a pH of 6. Then put 3 mL of each pH variation keeping columns the same pH. Finally put 3 mL of hydrogen peroxide without any buffer to alter the ph in rows A6-C6. Grab the forceps and pick up a piece of filter paper, dip that into the catalase for 1 second the drop it into the pH 6, record the time it takes for the filter paper to float repeat for a total of 3 trials. Repeat the dipping and dropping of the filter paper for all pH levels being tested. A6-C6 will be the control group.
Data
Title:
Data Analysis
The results display the data observed over the course of 3 trials per pH alteration. The dependent variable of the experiment was the actual time per pH of 6-9 of the catalase for the disk to rise to surface. The catalase disk time to surface peaks in pH 7 with an average of 4.66 seconds. The pH's above and below pH 7 that we tested seem to decrease in order. It was surprising in Trial 2 while testing pH 9 that it took 3.2 seconds to surface. This was just an outlier in the results because all the other data around the pH 9 had 2 or less seconds to surface.
Discussion:
by: Noah Roman, Cara Cronin, Aileen Ferrera and Lily Fajardo
The hypothesis was proven incorrect, as the reaction rate did not decrease in speed as the pH became more basic, or increased. Instead the reaction rate became slower as it approached the pH of 7. The reaction rate increased the further it was from pH 7. The pH of 7 was the peak as anything lesser or more's reaction rate was increasing. In terms of validity the results accuracy vary due to most likely a large human error. Human reflexes tend to be very unreliable because they are very inconsistent. Humans were in charge of stopping the stopwatch once the reaction was complete but as seen in the pH 7 trials the timing was very inconsistent.
materials visual
Discussion cont.
It appears that because initial reaction time was so rapid for the control group pH does affect the Catalase's ability to catalyze reactions with hydrogen peroxide. Even if human error altered the results there was clearly a more delayed reaction once pH was changed, which supports half of the hypothesis.
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