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Learn the toughest concepts covered in Biochemistry with step-by-step video tutorials and practice problems by world-class tutors

Review 1: Nucleic Acids, Lipids, & Membranes

Practice - Membrane Transport 1


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Let's finish up with some membrane transport questions. If you haven't done 32 yet, pause the video now for the process of solute transport. The constant Katie is analogous to K m from enzyme kinetics the the make a list meant in model and similarly lower case K t is analogous Thio Lower case cake hat. All right, looking at Question 33 in one catalytic cycle en aka at P ace transports three sodium out to potassium in and has to burn one ATP in order to complete this process So it converts at P two ADP and inorganic phosphate. And of course, this is a transporter. It's a I mean, it's a pump specifically located at the membrane, and you pump out three sodium molecules and then you bring into potassium. I'm sorry. I said molecules and ions. Then you bring in to potassium ions and this actually creates a, uh, essentially a net positive charge outside a negative charge inside. And this is due to the fact that even though we're just moving positively charged particles here, we're moving three positives out for every two we bring in. So that creates an imbalance, right? If we were moving three in and three out. We wouldn't be changing the charges at all, but because we moved three out and two in eventually you get net positive outside and negative. Inside. The movement of water across the membrane is facilitated by proteins, specifically channels called aqua por ins, and these selectively filter for water. They only allow water to pass through and these air basically essential to life. Because while water is capable of moving through the membrane by simple diffusion, it actually not enough water can pass through the membrane in order to sustain living processes. So aqua parents are essential for life because they allow water to pass through the membrane much, much faster. Moving on now to you. Question 35 Glucose transport from the small intestine. Lehman to the blood uses a sodium glucose import, and it uses a facilitated diffusion transporter, which is for glucose to be clear and basically what this looks like if we have our cell here and this will have like little free doodads on this side, here's the blood. Here's the Lumen of the intestine. This cell miraculously somehow knows to put on this particular side the glucose Sim Port glucose sodium Sim Port that's gonna take glucose and sodium in to the cell. And this works because in the Lumen you have a high sodium concentration, and in the cell you have a low sodium concentration. And you know why you have a low sodium concentration in the cell because of N aka TPS right? That is going to be pumping out sodium bringing in potassium God, This turned into a mess inside the cell. I have to delete the nucleus. There we go, K plus, there's our eye on anyhow, that is going to establish this Grady int right? And so, of course, out here, because all the sodium is getting pumped, you're gonna have high sodium out here, too. So that's why this simple it works and it's gonna bring glucose into the cell. And there's a lot of glucose in the cell, right? So that's moving against its concentration. Radiant, however, because there's a lot of glucose in the cell glucose contractual into the blood simply through facilitated diffusion. And that's because it's moving down, its concentration radiant. So it catches a ride in with sodium and then leaves via its own devices, moving on to question 36 a process not involved in the fusion of two membranes or to regions of the same membrane is the entry of glucose into the cells. I mean, we just talked about it's moving through a channel. This doesn't require any sort of membrane fusion event, whereas, and a psychosis is the membrane, basically pinching inward, sort of almost thought of his like cellular drinking, Exocet Assis is like cellular vomiting. Kind of. It's a vest ical, you know, fusing with the membrane and spilling its contents outward and entry of enveloped viruses into the cell, the virus. As it moves into the cell, it will actually pinch, um, penchants, um, membrane with it. And reproductive budding and yeasts also includes a membrane fusion. All right, let's turn the page.