Hi. It's Mr. Andersen and welcome to the AP Biology Lab 5 walkthrough. This is on cellular respiration. And in order to do that in eukaryotic cells we need this, which is the mitochondria. Basically what goes on in cellular respiration, I'm not going to go into too big of depth, but what we're doing is we're taking a sugar like glucose and in the presence of oxygen we're breaking that down into carbon dioxide water and we're producing energy in the form of ATP.
So what we're doing is we're taking a sugar like glucose and in the presence of Remember there are three different steps. We have glycolysis which is going to occur outside of the mitochondria. We have the Krebs cycle which occurs inside the mitochondria.
We're going to give off carbon dioxide and we're going to produce NAD and FAD. And then finally we have the electron transport chain where we're going to use the energy in NAD and FAD to make ATP or to generate ATP. But in this lab what we're really trying to do is measure the rate of respiration.
The rate of cellular respiration. And we do that by by measuring the rate at which oxygen is being consumed. And so in this lab set up we're going to use two different things. We're going to use worms.
And then we're going to use peas. Now you might think peas, well they don't respire. Of course they do.
In other words plants grow and they use photosynthesis to produce sugars. But then they break down that sugar to produce ATP and energy. And they're doing that so they can grow. And so since this pea is going to be underneath the soil.
It needs energy to grow. And it's going to do that through cellular respiration. Okay. So what do we use to measure this?
We're using something called a respirometer. A respirometer has important parts to it. It's got a glass jar here on the bottom.
Usually I'll put weights on the bottom so it's going to sink. And I'll get to that in just a second. On the bottom we're going to have some cotton. And that cotton is going to have this chemical in it.
It's called potassium hydroxide. Potassium hydroxide will be at the bottom of the pot. And it's going to be at the bottom of the have in this some absorbent cotton down at the bottom. Basically what potassium hydroxide does is if it's ever in the presence of carbon dioxide it will convert that into a solid.
In other words if we were to put peas inside here they would take in oxygen but they would produce an equal amount of carbon dioxide. And so that volume wouldn't change in here. But since we have the potassium hydroxide it's going to convert any carbon dioxide that's produced into this solid. So we really don't have to worry about its volume. Some other things that we'll use in this lab, we'll use beads to make sure that we can account for temperature changes or fluctuations and also to keep the volume the same.
And then we'll use an equilibration period. So basically how do you build it? At the bottom you're going to put some of the KOH, a little bit of cotton. Then you're going to put your pea seeds over the top of it. Then you're going to seal it and we're going to have a little pipette like this.
Now the three different types that AP suggests, oops let me go back for just a second. Okay. Now the three jars that AP suggests, we're going to have one where we're going to have peas in it.
Where we're going to have one where we have dry peas or non-germinating peas. And then we're going to have one where we're going to use just glass beads. Now these glass beads are simply a control.
These ones are used to subtract our values to account for just fluctuations in the temperature and how that affects it. So what we're really comparing is we've got germinating peas. And then we've got the dry peas. And then We've got non-germinating peas and then we've got worms. And so we're not really going to concern ourselves with this.
We'll use it to correct our values. But we're looking at the respiration rate of worms, germinating peas, non-germinating peas and see how that changes over time. So let's look what happens. We take our respirometer. We're going to put it under water and we're going to let it set and equilibrate.
And basically what you'll get is a little air bubble that forms right here. So there's going to be oxygen inside here. Oxygen is going to go all the way out here.
And then we're going to let it set. And then water is going to start to creep in over here. So now we let it sit.
So start at 0 and then 5 and then 10 and then 15 minutes. And basically what's going to happen is that P is going to start to consume oxygen. It's going to produce carbon dioxide. But remember that carbon dioxide will build up as a solid down here on the bottom so we don't have to worry about it. So we're going to decrease the amount of volume inside the respirometer.
And then the water pressure is going to start to move this bubble farther and farther and farther in. And so we can measure the rate at which this bubble flows in. And that's going to be the rate of respiration. It's kind of hard to read this under water because your eye is going to be right up here at the top. So you've got to get used to that.
But it's a really simple elegant experiment that we can use to measure respiration. What do we find? Well here's some data. So here would be the beads alone. Again we're using that to just accommodate for any changes.
Because temperature fluctuations are going to have a huge influence on this. We now got our germinating peas, dry peas and then worms. And so we can subtract any changes inside the beads from these other ones to account for any changes in temperature. But if you look at this person's data what they got is the steepest line, and they should all be linear, is going to be the germinating peas. So the germinating peas are going to have a line like that.
So this is the milliliters of oxygen consumed. Then it's going to be time on the bottom. So time in minutes. And so the slope of this line, if I were to figure out the slope of this line in milliliters of oxygen consumed over minutes, that's going to be the rate of respiration.
We'll find that that's a greater rate than that of the worm. and a greater rate than that of the non germinating peas. And that's because these ones are not activated.
They're not doing cellular respiration. If we were to soak them in water then they would start to activate and start to actually do those things. And so we could do the rate of each of those then graph it and that would be a histogram of the rate or the change over time.
And so that's the respiration lab. And I hope that's helpful.