Pressure Flow Hypothesis

by Jason Amores Sumpter
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Now that we've talked about how water moves through asylum, let's look at how sugar is transported through flow. Um, now the movement of sugars happens via bulk flow, and the sugars move from what's called the source to the sink. And the sources basically, uh, tissue where sugar enters the flow. Um, and a sink is tissue where sugar exits the flow. Um, and this whole process this bulk flow of sugars from source to sink is called trans location. Now, when sugars are loaded into the flow, um, or enter the flow and we call that flow um, loading and they enter via secondary active transport. What's what's gonna be used is a proton pump to create a proton Grady int. So here we have the outside of the cell. Here we have the inside. This is our membrane, and this proton pump is going thio pump protons out here and out here, we're going to have a high concentration of protons. This concentration radiant is going to allow this proton sucrose sim porter to bring sugar into the flow. Um, so it's going to move a proton down, its concentration radiant and at the same time, move a sucrose into the flow of against its concentration. Radiant, We call the uhh stuff inside the flow him Flow him, Sapp. And basically, it's mostly suit gross with, you know, some other dissolved sugars. And, you know, uh, a little bit of water and some hormones and minerals, But mainly, you know, what we have here is, uh, very sugary, mostly sucrose, like sappy, sticky material. Now, how this flow, um, sap is going to move through the flow. Um, is explained by the pressure flow hypothesis. This is the most commonly agreed upon theory for the movement of sap through flow. Um, essentially, the idea is this sugar is going to be more concentrated at the source, right. So here we have our source, which I'm representing with this little faucet icon. Their rights are source of sugar. It's our sugar tap. And I put it in a leaf because you know, leaf is gonna be one of those tissues that's going to produce sugars, and from there they will enter the flow. Um, here we have our Sim Porter. This is our proton super gross suit. Gross. Sim Porter. Here's our proton pump. So we're gonna load sugar into the flow. Um, and this is going to be our flow him over here. We have a Zeile. Um, now, what's gonna happen if, ah, lot of salutes in this case, sucrose wind up in the flow. Um, over here. What's that going to do? So what's that going to do to the salute potential compared to the asylum, that's mostly water, right? This is gonna be our low salute potential. We're gonna have higher salute potential over here. So water is gonna move from the asylum to its neighbor. The flow, um, due to the high concentration of sugar in the areas near the tissues that produce sugars. So this is going to cause an increase in ter ger pressure in the flow. Um, over here. So because of this movement of water, we're going to see ter ger pressure go up now down by the sink. Right, The sink. That's like your bum ass roommate. You know, they never do the dishes. They don't pull their weight. They don't do anything. They just take your stuff. The sink is going to just suck up all that sugar. So sugar is going to be way less concentrated down the sink, and that's actually going to cause water to leave the flow, um, and enter the asylum. So here our salute potential compared to the asylum is going to be higher. Are solid potential in the asylum over here is going to be lower compared to the flow. Um so over here water is going to go back to these asylum, and this means we're gonna have lower ter ger pressure there. So putting this all together, we have hi Turker pressure up here and low turker pressure down there due to water entering the flow him up here, leaving the flowing down here. And that's going to cause a positive pressure difference to build between the sink and the source. So we're gonna have a positive pressure potential compared down here, which means we're going to get bulk flow in this direction. So that's all I have for this lesson. Hopefully Now you have a good understanding of how water or I should say xylem. Sap moves through asylum and flow him. Sapp moves through, flow him. I'll see you guys next time