Class Data for Lab 6 - Catalase

This lab was challenging, but the data out of the "group of three" (Ted, Monica and Jimmy) allows us to analyze some numbers and come to some conclusions about enzymes.
Our numbers were drops of KMnO4. We "massaged" these numbers (by subtracting them from 200) and converted them into the enzyme's rate of reaction.  Let me explain:

Recall, the enzyme reaction in question is :    hydrogen peroxide + catalase --> oxygen gas and water
and the measurement reaction is:
                                     hydrogen peroxide + KMnO4 (purple/pink)  --->  water, oxygen and a colorless solution.

1) We added KMnO4 to see how much H202 remained in the cups. The more KMnO4 used, the more H202 is in the cup. So, we will call our drops of KMn04 a measure of how much substrate is present.
2) Unfortunately we had to choose an arbitrary baseline to use in our calculations. I chose 200 simply because it will work. This choice has a consequence, but it is not critical to our study.
3) By having a baseline of 200, we are saying that the cups started with 200 "units" of substrate. As the enzyme is allowed to work over time, the substrate levels decrease. The data does demonstrate a decreasing amount of substrate left in the cup -- and thus, we expect that we are indeed measuring the rate of the enzyme reaction.

In our graph we can label the dependent variable (the y-axis) "Substrate Used*" where the asterisk in the label should be explained at the bottom of the graph like this:

* = substrate used is measured in drops of KMn04 needed to react with remaining substrate subtracted from 200.

Exercise 2A, page 23. I boiled some catalase. When cooled and mixed with substrate and stirred, no reaction was observed. Use this data to answer question 2.

Exercise 2C, page 25. The number of drops needed to react with the remaining hydrogen peroxide was 3. Thus, it spontaneously decomposed over night at room temperature. We don't have a baseline to use here, but 3 drops means it was almost "spent."

I do want you to answer questions 2 - 5 in the lab book (page 28). Read number six. I am going to put it on this weeks quiz study guide!

Here is the notated class data, graciously supplied by the group of three listed above.

 10
 30
 60
 90
 120
 180
 360
Base line (arbitrarily chosen)
 200
 200
 200
 200
 200
 200
 200
Amount of KMnO4 consumed (in drops)
 161
 142
 122
 116
 109
 106
 106
Amount of H2O2 (substrate) used (in drop-equivalent to KMnO4) - this is the above lined subtracted from 200
 39
 58
 78
 84
 91
 94
 94


Now, for the graph on page 27. I recommend the following scaling:
    Y-axis : start with 20 (instead of 0) and extend to the top with 100. This means each square is 2 units on the vertical side. Label this "Substrate Used* - as indicated above.
    X-axis : start with 0 and extend in units of 10 seconds. Thus, you can mark off 100, 200, and 300 using 3/5ths of the x-axis scale.  Label this "Time in seconds"

Once the data is graphed, label each axis and give the title "Catalase Substrate Uptake Vs. Time" to the graph.
The shape of the graph can be explained as follows: in the first minute enzymes are finding and binding with substrate molecules and we see a sharp increase in the amount of substrate consumed. After another minute the enzyme must be maximally busy, with the rate of the reaction (the binding, reaction and unbinding) being the "bottle neck" to continued increase reaction rates. So, it flattens out as all the enzymes are busy and the substrate is just waiting in line.

Page 28. #1 The rates, based on the group data, are calculate like this:

Time Intervals in Seconds


 0-10
 10-30
 30-60
 60-90
 90-120
 120-180
 180-360
Number of seconds in the interval (this is delta x - the change in time)
 10
 20




Delta y -  is how the drops (substrate measurement) change between intervals.
Our first one is bogus because of our baseline.
 NA
 (58-39)=19




Rate (delta y / delta x)
19/20 = 0.95





Notice, I did the calculations for the first 2 columns. You need to complete the table. Here is a link to a word document with the table alone.