Alright, let's take a look at this example. It says, for the statements below, identify whether it applies to respiration in the alveoli, the tissues, or neither by writing the letter on the correct line. If the statement applies to respiration in both the alveoli and the tissues, write the letter on both lines. Alright, so we have 9 statements there, and then we have alveoli, tissues, and neither, and we got to write those letters down there. So let's start going through them one by one. Alright, first off, a says the site of internal respiration. Remember what that is. Now the site of internal respiration, respiration, the exchange of those gases, internal is down in the tissues. So I'm gonna put a there on tissues, exchanging the oxygen and carbon dioxide between those capillaries and blood and the tissues. Alright, so crossing out a. Next, we have b, the site of external respiration. Well, the site of external respiration. Yeah, it's in your body, but it's exchanging the blood with the external air in the alveoli. Alright, so b goes on the line oh, b for alveoli. Alright, next, we have the partial pressure of oxygen is about 6 millimeters of mercury greater than in the blood. Where does that happen? Partial pressure of oxygen, about 6 millimeters of mercury greater than in the blood. Nowhere. That oxygen gradient, remember, is always about 60 millimeters of mercury, not 6. It's a really big gradient and that 60 is both in the tissues between the blood and the tissues, and in the alveoli between the blood and the alveoli, just in opposite directions. Alright, so c, I'm gonna write that on neither. Alright, next, we have the partial pressure of carbon dioxide is about 6 millimeters mercury less than in the blood. Alright, well, now we're talking about the partial pressure of carbon dioxide, and here again it says 6 millimeters mercury less than in the blood. Where is that? Alright, well, that means carbon dioxide is gonna be moving down its pressure gradient from the blood to this space. So carbon dioxide leaves the blood in the alveoli. So I'm gonna write d on the line here. The partial pressure of carbon dioxide is 6 millimeters mercury less in the alveoli than in the blood. Alright, next, we have the partial pressure of oxygen is more than twice the partial pressure of carbon dioxide. Alright, where does that happen? That happens in the alveoli. Alright, remember, partial pressure of oxygen in the alveoli was like 104 millimeters of mercury, and partial pressure of carbon dioxide in the alveoli was about 40. That is more than twice the partial pressure, so I am putting e on the line for alveoli. Alright, next, we have f. The partial pressure of carbon dioxide is more than twice the partial pressure of oxygen. Where does that happen? Nowhere. Alright, so I'm putting that f on neither. Right? Where the partial pressure of carbon dioxide is greater than oxygen is in the tissues, but there the partial pressure of carbon dioxide, we said, is about 46 millimeters of mercury and the partial pressure of oxygen is about 40. So it's definitely not twice. Alright, so crossing out f, that brings us to g. We said g, there is a net release of oxygen from the hemoglobin. Alright, where does that happen? Where does hemoglobin release its oxygen? That's gonna happen in the tissues. In the tissues, right, the oxygen gets released from the hemoglobin, enters into the plasma, and then from the plasma, it goes into those tissues. Alright, we have h. There's a net movement of carbon dioxide into the blood. Where does that happen? Alright, well, carbon dioxide moves down its pressure gradient from the tissues into the blood. So again, we're gonna put tissues here. h is where there is a net movement of carbon dioxide into the blood. Alright, and then finally, we have the net movement of total oxygen and carbon dioxide molecules will be approximately equal. Where does that happen? Right, well, we said that both in the alveoli, so I'll put an I here, and in the tissues, you expect the total number of oxygen and carbon dioxide molecules exchanged should be about equal. And we said that's really just a factor of cellular respiration, what we use to break down our food molecules and capture ATP, because that equation uses 6 oxygen molecules and produces 6 CO2 molecules. That's an equal number, and so that's where all these molecules are going to or coming from. So in the end, the exchange should be roughly equal in all places. Alright, hopefully, you were able to straighten all that out. We have a few more practice problems after this. I'll see you there.