 I'm going to draw you a picture of Photosystem 2 and I'm going to draw Photosystem 2 first. Photosystem 2 was, and I'm going to call it PS2, it was discovered second, but the events in Photosystem 2 happen first. You will see that we have like this chicken egg like weird problem with Photosystem 1 and Photosystem 2. I'm going to try to put them on the same page, but we're going to talk about them in separate sections and you'll see how after we get all the pieces laid in, you'll see how they're super related. We can't really separate them that well. I'm going to draw you the Thylakoid Lumen and that means that this is the green line I've drawn is the Thylakoid membrane and at the top here, this is all stroma. Okay, do you have context for where we are? I'm going to go back to our drawing of the chloroplast just for like, it's almost like I drew that box right there. Do you see that? I just blew it up. So all we see is one line and there's my line with the stroma oops, whoa, no, don't settle down. I'm feeling a little goofy. Can you tell stroma on top, Thylakoid Lumen on the bottom. The first thing I'm going to draw for you is my Photosystem photosystems must be green and I'm drawing it. Please forgive this. This is in no way like in zero ways, anatomically accurate. This is how I visualize a photosystem because it's basically a light funnel, watch. This is Photosystem 2. Don't forget we're talking about Photosystem 2 first and I say that out loud for myself because I forget all the time. Photosystems are light funnels. So here's light energy that's coming in. It is literally funneled to an area. The light is funneled into the middle of the photosystem. This middle zone is called the reaction center. I cannot draw that there. It's the reaction center and I'm going to tell you what happens in that reaction center. But what is a photosystem? Well, it's basically a bunch of chlorophyll. Chlorophyll is a pigment. It's what makes a plant green and it's a photosensitive pigment and all these chlorophyll molecules, there are other pigments in each photosystem, but most of it is chlorophyll. Because it is photosensitive, it reacts to the light and because of something that I will only say is like a funnel. The energy from the sun is funneled to that center spot that is like it's the reaction center. All the light from the sun is used in the reaction center to create two high energy electrons. Now, because I am a storyteller, there are my electrons, I'll go ahead and circle them. They're just sitting in the photosystem. They're sitting in the reaction center and they're just regular electrons. And the light from the sun is funneled in through chlorophyll, thank you very much, and that energy goes into those electrons. This is, again, diagrammatic or it's a rigged story, but I imagine it's like a trampoline. And as the light funnels into the trampoline, it gets bouncier and bouncier in there for those electrons as they get more and more energy and then pretty soon they get enough energy to fling out. And now, when those electrons, because they collected energy from the sun, they are now what would you call them? They were regular Joe electrons in the photosystem, but with a little bit of sunlight, they are now high energy. Are they high energy electron carriers? No sillies, they're just electrons and they're flying high because they jumped on the sun fuel trampoline. What would be something that we could do with high energy electrons? Are you just going like, it's true, I've seen that before. I know what we could do with those high energy electrons. You do. Dude, let's pass them to an electron transport chain and that's what happens. They became high energy electrons from the sun and then we're going to use those high energy electrons to pass them down an electron transport chain. Now, what story do you already know about those high energy, those proteins in the electron transport chain? What are they going to use the energy for, home kids? What do you think? I'm telling you it's as easy as you think. You know the story already. This time, we're pumping, we're using the energy to pump hydrogen ions or protons into the thylakoid lumen. We are creating a high concentration of hydrogen ions inside the thylakoid lumen. Hmm, why would we want that? What good is a hydrogen ion concentration gradient? Whom am I going to draw next? I would get ice cream for whoever can guess who's this guy. Oh, it's our buddy. I feel like, what, you're back, I missed you. ATP synthase is there saying, did somebody say hydrogen ion gradient? I can help with that. And when those hydrogen ions want to get out, what does ATP synthase do? Dude, I'll let you out if you pay a little tax as you go. And then I can turn ADP plus P into what? You already know that story, don't you? Photosystem 2 captures light from the sun and uses that light to produce ATP. And you could explain with your eyes closed how that happens, because you've already seen it. Great strategy, all right? One of the things, one of the problems that we had in cellular respiration when we rocked a electron transport chain, it was a problem solved by oxygen in that case, what was it? We needed a final electronic scepter. This is going to be the final electronic scepter in this situation. It's not oxygen. And it's not, it's not anybody else. It's Photosystem 1. I'll be right back and we'll do Photosystem 1.