So now that we've covered secondary active transport in this video, we're going to talk about a specific example of secondary active transport, and that is the glucose active supporter model. Now, this is a classic and relevant example of secondary active transport, and more specifically, we're gonna be looking at the intestinal epithelial sodium glucose sim porters. And so, just to get a better idea of exactly what we're talking about, one we're referring to intestinal epithelial cells. Let's take a look at our image down below. And so notice that we've got our anatomical figure over here and we're zooming into this specific region and you can see that we have the stomach, the pancreas and the intestinal Lumen right here. And so if we zoom into the intestinal Lumen wall right here in this region, which will notice, is that the wall is made up of these villas structures that you see right here these curved structures that give mawr surface area to the intestinal Lumen and allow for better absorption of materials that we eat. And so what you'll notice is that these ville I are lined with a bunch of individual intestinal epithelial cells and also these ville. I are closely associated with our bloodstreams which we have right here in the villa. And so if we zoom into this particular region over here on the right hand side of our, uh, ville, I notice that again zooming in will show a bunch of individual intestinal epithelial cells and these little structures that you see here would be the micro ville. I again allowing cells to increase surface area and increase their absorption of materials that get into our intestines. And so notice that now we're zooming into one individual intestinal epithelial cell here, and that is going to be this image that you see down below. And so really, this image down below is the main image for this lesson. And all of the other image images are just there to give you guys a little bit of context. And so if we go back up to our lesson, which will notice is that this intestinal epithelial sodium glucose importer really has three important components that you guys should know and we've labeled each of these three components as a B and C and you'll be able to see each of those three components corresponds with the images that we have down below so you can see component. A is right here. Component B is over here, and components C is right here. And so, of course, we know from our previous lesson videos that secondary active transport is indirectly driven by primary active transport. And so that's exactly where we start with Component A is primary active transport, and more specifically, it's actually the sodium potassium pump that is going to maintain a trans membrane sodium Grady int and this trans membrane sodium Grady int we know is going to be really, really high on the outside of the cell and really, really low on the inside of the cell. And so if we take a look at our image down below at component A over here, notice that it's just the sodium potassium pump that we talked about from our previous lesson videos. And so we know that it hide relies is 80 p, and in the process it transports three sodium ions to the outside of the cell as it transports to potassium ions to the inside of the cell. And so again, this is establishing a concentration Grady int for sodium. That is really, really high on the outside of the cell and really, really low sodium on the inside of the cell. And so that transitions us directly into the secondary active transport. Part of this lesson, and that is exactly where the sodium glucose importers come into play. And so the sodium glucose importers are going to co transport, as their name implies, sodium and glucose in the same direction across the membrane. And that's what makes them sim porters, because the two molecules are being transported in the same direction. And so really, what powers? The transport of this co transport here is that there are two sodium ions that are gonna be imported down their concentration Grady INTs or with their concentration radiance from high to low and these two sodium ions being imported down their concentration. Grady INTs is really what powers the movement of one glucose molecule being imported into the cell against its concentration Grady int from an area of low concentration to an area of higher concentration. And so if we take a look down below at our image, noticed that we have component be up here at the top, right and This is our sodium glucose importer, our secondary active transporter model, and so notice that no a teepee hydraulics is's directly involved here with this sodium glucose importer. So we know it's got to be a form of secondary active transport, and it's utilizing the Grady INT that was established by the sodium potassium pump, the sodium Grady Int that was established. So there's low sodium on the inside and high sodium on the outside. And so, as sodium gets imported down its concentration Grady int from low to high, it's powering the movement of glucose from the intestinal tract into the intestinal epithelial cell against its concentration Grady int. And so now that transitions us to the last part here of our lesson, part C. And that is just to know that as glucose is pumped into the intestinal epithelial cell from the intestinal track to the inside of the cell, it's also simultaneously being moved into the bloodstream via a glute to uni porter. And of course, we know uni porters will transport one molecule in one direction across the membrane, and that is going to be glucose. And so if we take a look at our image down below, Noticed down below part. See, here we have the glue to Uni Porter, which is going to transport glucose, uh, in one direction across the membrane so that it can diffuse into the blood. And, of course, once glucose is in the blood, that glucose can diffuse to pretty much every cell in our bodies. And so one thing to note here is that the sodium glucose importer that we talked about in part B and this, uh, glued to uni Porter that we just talked about in part C are actually operating on opposite sides of the intestinal epithelial cells. And so if we take a look back down below notice again that the sodium glucose importer is operating on the intestinal tract side of the cell and notice that the glute to uni porter is operating on the opposite side of the cell that's closer to the blood stream. And so all of these systems here are operating together to allow glucose that gets into our digestive system when we eat foods and transport that glucose from our intestinal track into our intestinal epithelial cells and then through, uh, the intestinal epithelial cell into the blood where again it could be transported toe every cell in our bodies. And so really, it's this sodium glucose importer here that is our example of secondary active transport. And really, this is the conclusion of our lesson on glucose active supporter model, and we'll be able to get a bunch of practice and our next couple of videos, so I'll see you guys there.
2
Problem
The Na+-Glucose symporter transports the two molecules into the cell, while the Na+-K+ ATPase uses ATP to transport Na+ ions out of the cell. What would be the result of a mutation leading to a nonfunctional Na+-Glucose symporter?
A
Increased levels of intracellular K+.
B
Increased levels of intracellular glucose.
C
Decreased activity of the Na+-K+ ATPase.
D
Overactivation of the Na+-K+ ATPase.
E
Increased levels of ATP.
3
Problem
Imagine that you perform a series of experiments to test the rate of glucose transport (V0) into epithelial cells using the Na+-Glucose symporters. These experimental epithelial cells contain no intracellular Na+ but have the same glucose concentration as their surroundings. In experiment #1, you transfer your cells to test tubes that contain different extracellular [Na+] & then measure the rate of glucose transport (V0). In experiment #2, you introduce leakage Na+ channels into the cell membranes & then repeat the same experiment. Label the data on the plot below as showing results to either Experiment #1 or Experiment #2.