Today, we are going to be doing an experiment that is part of the
biology complete solution.
Today's experiment is going to be enzyme action where we are going to test the
activity of catalase.
For this experiment, we are going to be using the Go Direct O₂ Gas Sensor.
The Go Direct O₂ Gas Sensor comes with a Nalgene bottle, which is what we are going
to be using to run our experiment in.
Also for this experiment, you're going to need a source of enzyme.
Today, I am using yeast as my source of catalase.
To create this solution, I used one packet of yeast in 100
milliliters of water with about 7 grams of sugar that I let sit on a
Stir Station overnight.
We are going to be using catalase to break down 3% hydrogen peroxide,
which is something that you can easily find at any drugstore.
So to first set up this experiment, what we need to do is first launch
Graphical Analysis on our Chromebook.
And then you're going to click or tap on Sensor Data Collection.
Once you've launched Graphical Analysis and then click or tapped on Sensor
Data Collection, make sure that your Go Direct O₂ Gas Sensor is on.
And then you're going to look for it in your list.
Once it shows up, you're going to click or tap on it to connect.
Once it's connected, you can then click or tap Done.
And now, we are ready to set up our full experiment.
The first thing we want to do in this experiment is actually change our data
collection rate and duration.
So I'm going to click or tap on Mode.
And we are going to change our rate from 1 sample per second to 0.25
samples per second.
In other words, we are going to take one sample every four seconds.
Then, we're going to change our duration from 300 seconds to 180 seconds.
Once you've done that, you can then click or tap on Done,
and we are ready to proceed with the experiment.
First, we're going to use our 3% hydrogen peroxide and measure out five milliliters.
Then, we're going to add that to a test tube.
And then, we're going to add five milliliters of distilled water.
And then add that to the test tube.
This has essentially now diluted our 3% hydrogen peroxide now
to 1.5% hydrogen peroxide.
Once we have that solution made, we are then going to add our enzyme.
The key here is to make sure you test your enzyme before your students
do this experiment.
Since we are using yeast as our enzyme source, the yeast can actually be quite
variable in the amount of activity they can have.
So you want to make sure ahead of time that you have your students adding the
appropriate amount of enzyme to get the correct reaction rate.
Since I tested this previously, I know that adding five drops to my 1.5%
hydrogen peroxide solution is the appropriate amount for my
initial reaction rate.
Also, I have my yeast solution on a Stir Station to ensure that it is thoroughly
mixed and that I get an even amount of yeast every drop I take.
So I'm going to use a pipette, and take from the center of my solution,
and I'm going to add five drops.
Now that I've added the five drops, I'm going to mix it a little,
and then I'm going to add this to my Nalgene bottle.
But for this experiment, to help ensure I get great results,
I'm going to add a stir bar, and I'm going to be using it
on a Stir Station.
So I add my solution, and then I'm going to go ahead and put my
O₂ Gas Sensor into my bottle.
Now, I want to wait about 30 seconds to ensure that the gas that's produced
starts to fill the bottle and can be sensed by my Go Direct O₂ Gas Sensor.
So after about 30 seconds have passed, I'm going to go ahead and click or tap
on Collect to start our data collection.
You can see already, after a little bit of time,
that our oxygen gas values are already increasing, showing us that the enzyme is
indeed breaking down our hydrogen peroxide into oxygen gas and water.
Now, that data collection is complete, we can go ahead and stop our Stir Station,
and remove our O₂ Gas Sensor from the chamber.
And the chamber can go ahead and be rinsed out to be prepared to use for another run.
But since we already have data on our Chromebook, let's go ahead and analyze it
and see what our reaction rate was.
To do that, we can do a line of best fit that can give us a linear equation
to determine what our rate or the slope of the line is.
So first, we're going to click and drag to highlight the region in the graph
we want to analyze.
And then I'm going to click or tap on Graph Tools.
Then, I'm going to click or tap on Apply Curve Fit , and I'm going to make
sure that Linear is the fit that is selected.
And then I'm going to click or tap on Apply.
You can see my line equation has now been displayed on my graph.
And if I look at my slope of the line here, that is going to give me my initial
reaction rate of the enzyme activity breaking down hydrogen peroxide.
So from here, students can then add more enzyme to see what happens to the
reaction rate, as enzyme amounts increase.
Students can also further investigate other variables such as the effect of pH.
Or if you have access to 6% hydrogen peroxide, students can also see the effect
of higher concentrations of substrate.
We use yeast as our source of catalase, but there are other sources of catalase
you can use as well.
One of the sources you can use is actually purified catalase that you can purchase
from scientific supply companies.
This is a great way to actually use a defined amount of the enzyme,
so students can actually calculate how many units of enzyme are used
in each reaction.
For more information about this experiment and our complete biology solution,
please visit our website .