Secondary Active Transport

Jason Amores Sumpter
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So now that we've covered primary active transport in this video, we're going to focus on secondary active transport and so recall from our previous lesson videos that secondary active transport is not directly driven by a teepee hydraulic sis that is primary active transport. Instead, secondary active transport is going to be directly driven by another molecules concentration Grady int, and it's going to be powered by another molecules concentration ingredient instead of being powered by a teepee. Hydrologists like primary active transport ISS. However, that being said secondary active transport. Although it may not be directly driven by a teepee hydraulic sis, it is indirectly driven by primary active transport and a teepee. Hydraulics IHS. And the reason for this is because the concentration ingredient that directly drives secondary active transport is actually built using primary active transport or P A. T, which we've abbreviated here for our lesson. And so, in order to better understand secondary active transport, we're actually going to take a look at a classic example and the sodium glucose secondary active transporter and so down below. We have an image of this sodium glucose transporter and notice that the image has these numbers 123 and four. And these numbers that you see down below and the image correspond with numbers that we have up above here, in the text. And so this is really showing you the four steps that there are for this sodium glucose secondary active transport example. And so in the very first step here, which you'll notice is that sodium ions can be transported against their concentration. Grady int using primary active transport. And so when you take a look at our image down below, noticed that the sodium ion, which we're showing you down below here in step number one, um, is being pumped across the membrane in this direction, and it is being pumped towards the area of higher sodium concentration, whereas down below there's a lower sodium concentration inside the cell. And so because sodium is being pumped against its concentration radiant from low to high concentration, it's going to require energy and noticed that a teepee is directly linked to this process of pumping sodium across the membrane. And because 80 p is directly linked here, it is a form of primary active transport. Just like what we mentioned up above, sodium being transport against this concentration, radiant using primary active transport. But we've already covered primary active transport, so really, this is not anything new to us. And so, essentially in number two, what this is going to generate is a higher concentration of sodium ions generated on the outside of the cell. So the outside of the cell here has a higher concentration of sodium. You can see there are way more sodium ions much, much, much higher concentration than there are inside the cell. So there's a lower sodium ion concentration inside. And this is because again, this primary active transport generates this concentration Grady of sodium. But then what? We need to also realizes in this image and number three, there's another molecule that's also involved here glucose, which we have in green, and so notice down below. We have glucose as well. We have thes green hexagons here and also down below here, and notice that the glucose molecules they actually have a higher concentration on the inside of the cell, which is opposite to that of the sodium. The sodium has a higher concentration on the outside of the cell. The glucose has a higher concentration on the inside of the cell. And so this is really where secondary active transport comes into play because sodium eyes going to be transported down its concentration ingredient from an area of high concentration to an area of low concentration, and that does not require any energy. In fact, it actually can provide and release energy. And so, as the sodium gets transported down its concentration Grady Int, it's actually going to provide the energy. It's going to power the transportation of glucose against its concentration ingredient, from the area of low concentration of glucose towards the area of high concentration of glucose. So once again, to better understand this, let's take a look at this example over here, and what you'll notice is that sodium is going to be transported down its concentration Grady int from an area of high concentration down towards an area of low concentration and that does not require any energy for molecules to move down their concentration. Grady Int. Instead, it's going to release energy and that released energy can be used to power the movement of glucose against its concentration. Grady int from an area of low glucose concentration on the outside of the cell towards an area of much higher glucose concentration on the inside of the cell. And this is really ah type of active transport, since molecule is being transported against its concentration. Grady int. But notice that no a t p. Is directly involved. Notice there's no 80 p in this vicinity at all. And so because it's not driven directly by a TP, it's going to be driven by the concentration Grady int of sodium being transported down its concentration Grady Int. And so that makes this a classic example of secondary active transport. And so, once again, as we mentioned up above with secondary active transport, it's gonna be driven by the concentration Grady in of another molecule instead of a teepee hydraulic sis. So over here with secondary active transport notice that there's no 80 p at all in this vicinity on really, it's just this concentration Grady in of sodium, going down its concentration that powers the secondary active transport here of glucose being transported against its concentration Grady int. And so this year concludes our introduction to secondary active transport, and we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video