Membrane Transport 3

The last type of membrane transport that you need to be aware of comes in the form of ionophores and these air molecules that can transport ions through the membrane. Uh, many of them are lipid solid molecules that bind ions and actually move them through the membrane. Some are actually molecules that create little pores in the membrane that allow ions to pass through. Most of them are toxins, however, and if you think about it ourselves, expend energy and work very hard to move ions in specific directions, right? What? The purpose of a lot of those pumps is to establish specific electrochemical radiance. And so these ionophores kind of come in and muck up all that hard work by allowing the ions to move against the direction that the cell wants them thio. And again, even though we've talked about all these different types of transport, um, in sort of discrete in a discreet manner, you have to realize that all of this transport is going on together all at once, and it gets very complicated. And so, uh, you know, establishing proper transport becomes a very sophisticated matter for the cell and a great example of this is in our digestive tract. Um, the cells of our intestine have two sides. There's the side that faces the interior of the intestine or the intestinal Lumen. And then there's the side that faces the blood. And we actually have to place specific transporters on the different sides in order to carry out the functions necessary to absorb nutrients. And if this didn't work, we would die. I mean, we just wouldn't be able Thio absorb any glucose. We wouldn't get any energy for ourselves. And it's actually still a mystery in biology how cells know how and where to place the various transporters. But it works were alive, so thank goodness for that. And let's take a quick look at it. So basically, you have high sodium concentration in the intestinal Lumen, and this sodium glucose importer exploits that and moves sodium down. It's electrochemical radiant, so there's lower concentration inside the cell. It moves sodium down. It's gravy int, and glucose gets taken along for the ride. Then, on the other side of cell, we have the sodium, potassium pump, n a, K T. P s, and that is going to pump actively pump sodium out of the cell to make sure that the concentration inside stays low and that's going to you, of course, build up concentration out here and then because glucose is transported actively or using secondary active transport into the cell, it actually just has to use facilitated diffusion. Thio exit the cell so pretty incredible. And this is just one small example. You have to think that there's, uh, many, many other processes just like this happening all the time in all ourselves, pretty mind boggling and awesome. Now, last thing we need to talk about is transport kinetics and very fortunately for us, this is super easy because transport kinetics are basically exactly the same as Michaelis meant an enzyme kinetics. We just have to change the names of a few things. So, uh, here is our graph this is straight out of McAllister meant an enzyme kinetics, and we're just gonna change a couple names around to make it work for transport kinetic. So we're not dealing with a reaction anymore, right? We're dealing with the movement of salutes so we can just call this saw you entry like salute entry into the cell. Of course, it could be you know, saw you leaving the cell or something. Um, you know, that's kind of an arbitrary distinction. Eso this is salute entry into the cell instead of substrate concentration we are going to have. So you concentration right with me So far. All right. Now, let's get a little fancier instead of k m, we're going to have capital k t. And basically Katie is just like a m k t or K m was Theseus substrate concentration at which the reaction rate hits half the maximum rate. Katie is the solute concentration at which uhh solid the rate of solid entry hits half the maximum rate, right? It's pretty straightforward stuff. The last thing we need to know about is que lower case K t. Which is the equivalent basically of K cat. So if you remember, K cat is the time it takes for one molecule of substrate to be turned into product. Katie likewise is the time it takes for one molecule of salute to be transported Simple. Is that so? Hopefully transport kinetics should be super easy for you guys because you're very familiar with Nicholas meant an enzyme kinetics. And yeah, that's all I have for this video. Siri's good luck on your exam