[Enzyme Activity]
Roger: Well, let's take a look and see what kind of speed a reaction is going to happen at.
We'll take a look at a specific reaction, and we'll change some conditions
to see what's going on to make that reaction speed happen at different rates.
Barbara: This reaction is hydrogen peroxide breaking down when you add a catalyst.
This catalyst is made from one packet of yeast, seven grams of yeast,
in 500 milliliters of distilled water.
The hydrogen peroxide solution, this is our substrate.
This is the thing that we're breaking down.
We got three percent hydrogen peroxide from the grocery store
and just diluted in half to get 1.5 percent hydrogen peroxide.
Roger: So you just mixed half of hydrogen peroxide and half water.
Barbara: Yeah. Do you ever wonder why is it in a brown bottle?
Roger: That's going to be a good question for them to address.
Barbara: Something to look into.
Roger: Excellent. Here's our solutions already premixed.
Barbara: I'm just going to get 20 milliliters of that hydrogen peroxide
and put it in the bottle.
You'll notice that I have a magnetic stirrer here.
My yeast suspension is being continuously stirred.
If I did not have a magnetic stirrer for this, we'd have to stir this by hand
before we got any of that sample.
But the first run, we're just going to look at the natural background spontaneous decomposition
of hydrogen peroxide without putting an enzyme in it to speed it up.
Go ahead and grab 20 milliliters of hydrogen peroxide.
Roger: Here you go.
Barbara: Thank you.
Barbara: OK. No enzymes.
This is just substrate.
Then we're turning on.
Roger: Now that it's stirring, what I'm going to do is go over to my SPARKvue software
and we will start that up.
We've already taken the time to calibrate it through the live data view
here in the bottom left, but I'm just ready to start measuring.
Here we go.
How long will we measure this just to follow?
Barbara: Three minutes is good.
The sample rate, I think it's one hertz. That means one sample per second.
It's a bit loud.
Roger: That's the default, so that's an easy thing to set up.
All right, we'll watch this go by in quick motion for the next three minutes.
Roger: Now that we've come to three minutes, we'll slow the stirring down
and we're going to stop the data collection.
You're going to want to find out how much oxygen has been released in this reaction.
The easiest way to see some of these high and low points is to see it spread out
using the scale to fit.
Then your job is to go in and use the data to find out
how fast that rate is of the oxygen coming off.
Barbara: How might you find a value for a specific data point in SPARKvue?
Roger: To find the top-end data point, or the low-end data point,
so you can determine that rate, we'll use the coordinate tool that should show up.
You've got a couple of ways to move that.
You can, if you feel like you're in a good spot, just to move it a little bit
using the left and right tools.
You can then find what the lower end in this case is.
But then you use the second coordinate tool, or you can put that coordinate tool up to
where the highest value is and find the difference between those through your own math.
Barbara: OK. Are we ready for the second run?
Roger: Let's do this.
Barbara: So we got our control run here with no enzyme added,
with our background decomposition rate of hydrogen peroxide with no catalyst.
I need to clean the beaker, so that I can recreate the original condition
as much as possible, with some water.
I'm going to rinse this. Rinse it down.
This is just tap water, or rather, it's distilled water.
One water just for...and spilled a little bit.
I'm going to pull out the magnet.
Roger: While she's cleaning that up, I'm going to go ahead
and measure out another 20 milliliters of the peroxide.
Barbara: But this time when the substrate is in the container,
we're going to add the enzyme.
Two milliliters of enzyme using a graduated pipette
so I can quickly deliver the catalyst into the container
and put the sensor on, and quick as we can,
we're going to start data collection, so we don't miss anything if anything happens.
Roger: I'm going to double check to make sure that I have 20 milliliters.
You can see I'm a little low because the bottom of the meniscus
is not quite to the 20.
Let's add a couple more drops.
There we go.
I can see the bottom of the liquid solution, there is showing a 20.
I'll give that to you to be able to measure these in here.
Barbara: I already got the magnet in there, so we're good.
We're going to try to get this ready to quickly deliver that catalyst,
and then we're going to close it as fast as possible.
Actually, Roger, would you be able to slide this down as quick as...
Roger: Absolutely.
Barbara: Great, because that'll help out.
Roger: Should I start the data collection?
Barbara: Let's wait until it's closed.
Roger: Now we're going to add the catalyst.
Barbara: And I'm going to get two milliliters.
Ready?
Roger: I'm ready.
Barbara: Let's start the stirrer.
Ready, set, go.
Go ahead and start.
Roger: Start a second run.
Barbara: Cool.
Roger: Again, we're going to run it for three minutes.
Barbara: We'll speed up the video for you.
Roger: All right. You can see that the oxygen is coming off nicely.
We're going to slow the stirring down,
and then I am going to go ahead and stop that collection.
If you want to be able to compare these two directly,
you can turn both runs on by just putting a check mark into that same system.
At this scale, you can see quite a drastic difference between these two reactions.
Again, you're going to then take two points and use the coordinate tool
to find out a low value and a high value from which you can determine your rate.
Barbara: If you need to go back and do some analysis on run one, just make sure that you
move the red box that's around the pink diagram for run two on to run one.
Roger: You should be ready to start and do your lab.
Barbara: OK, good luck.
Roger: Thanks.