 So the first thing we probably want to figure out about photosynthesis is where it takes place. If you remember, we really focused in on the mitochondrion when we talked about cellular respiration. And much of cellular respiration takes place in the mitochondria. Not all of it. Remember, what part does not take place in the mitochondrion? That would be glycolysis. And glycolysis happens in the cytoplasm of a eukaryotic cell. In our eukaryote, all of the stuff happens in the chloroplast. So let's go ahead and define or draw or whatever chloroplast. Let's do some chloroplast anatomy first as the first part of our big picture since everything that we need to know is happening inside the structure. Okay, remember the chloroplast is a membrane-bound organelle found in plants and plant-like protists. The chloroplast is actually really similar to a category of bacteria. I can't remember if they're blue-green bacteria. I can't remember who they are. But there's a group of bacteria that are really similar to these guys just like there was a group of mitochondria. I mean bacteria that are really similar to mitochondria, which is interesting and interesting thing to think about. Also like mitochondria, the chloroplast has a double outer membrane. What do you notice about the inner membrane that I just drew on this chloroplast? We have two membranes, super important, but what's something that's different that you should notice right away? Remember our mitochondria? I can't help it. I have to draw you a mitochondrion. Two membranes, but what was true about that inner membrane? Holy, folding mess. Like it was a crazy high surface area folded inner membrane. Not the case with the chloroplast. We have the double membrane, but that inner membrane is flat. And actually we're not going to bother ourselves with the inner and outer membranes. Interesting that both of them have these two membranes, but the membranes aren't involved in the process of photosynthesis. So you might be like, awesome, this is going to be easier. Well, perhaps you shouldn't make that assumption just yet. Instead, inside, and I'm drawing these big so that we can label them inside the chloroplast. There are these membrane, what, bags? Stacks of bags? Almost like the Golgi body. Remember how the Golgi body was like stacks of pancakes? It's like they're stacks of bags. I've heard them described as like stacks of coins, green coins. The stacks have a name, so one whole stack is called a granum. This, the anatomy of a chloroplast is like, it's more than the anatomy of the mitochondrion. There's more terminology here. So the stack of sacks, the whole thing is called a granum. How many grana do we have in my chloroplast? That would be two. Two grana. Grana is plural. Granum is singular, but they mean the same thing. And of course, each sack has a name. So each little individual sack is called a phylochoid. So, granum number one has three phylochoids. Granum number two has three phylochoids. Are you good? And each phylochoid, I said it was like a sack. It is so. It is a sack and it has a space inside because all sacks have spaces inside. That's what makes them a sack. This sack space is called the phylochoid lumen. And I have words to say about this. Phylochoid. I'm going to put that in parentheses because it really is just the lumen of the phylochoid. Let's take a minute. Let's take a minute to say, dude, really, there's a lot of words here. Lumen is a word that we will see again. If you travel to anatomy, you will see it a lot because a lumen is a general term for any space inside a tube. Or maybe I should also include a sack. A space inside a tube or sack. Do you have, do you spell sack with a C or is there a K on there as well? I seriously have no idea. You can spell it however you want. I will not mark you off for how you spell the word sack. Maybe I should pick a different word. Bag. I know how to spell bag. All spaces have, all bags have lumens. Your stomach is a bag that has a lumen. So there's the lumen of your stomach. Your esophagus where your food travels down has a lumen. There's a space in there and your food goes through it. Your trachea has a lumen. There's a space in there and air goes through it. You're full of many lumens. And actually plural of lumen is lumina. I don't know. I did just remember that just now but I don't think I'm going to use that very often. The point is the thylakoid has a lumen and this is a space that's important. What was the space that was important in cellular respiration? I'm giving you time to raise your hand. I'm calling on you. So answer, say it out loud. The space that we used in the mitochondria was the intermembrane space. It was the space, oh I guarantee that this is way too small for you to see, right? But it's the space between the inner and outer membranes. That space is present here but we don't care about that space. The space in the thylakoid, the lumen of the thylakoid we do care about. Can you like predict maybe some things that we might do with that space? That's awesome. I hope you can. The last thing I want to tell you is the name of the cytoplasm in the chloroplast. Do you remember the name of the cytoplasm in the mitochondria? It was the matrix, the mitochondrial matrix. And remember didn't Krebs cycle happen in the mitochondrial matrix? And then the electron transport chain happened in the inner membrane, the inner membrane. And then they pumped all the protons into the intermembrane space, right? The mitochondrial matrix is the mitochondria's cytoplasm. The stroma is the chloroplast's cytoplasm. These are the places, the thylakoid lumen and the stroma. These are the places that are going to be significant for our big picture story. Now, remember, remember that we have like the whole point of photosynthesis is to somehow capture light energy. It doesn't have to be the sun but I just like drawing sun shines. And we're going to capture that light energy and use that light energy. Transfer the light energy into the chemical bonds of a glucose molecule. That's the end game. In order to pull that off, I think I'm going to have to move this over a little bit. Oops, bear with me while I move this. That way I've got a little more room. I've actually been drawing before with like a real pencil and tried to change my real pencil tool to move. It doesn't work that way. All right. In order to get the glucose at some point, you have to put in... This is so exciting. I just don't know what color to use. The carbon is an important part. There is no carbon in light energy. So where does the carbon come from? Carbon dioxide. This process right here, this is taking carbon dioxide gas and turning it into glucose, an actual glucose molecule. It's magic y'all. And holy cow. The thing that comes out of this process, what gas comes out? The oxygen comes out and we have a whole little piece at the very end of this lecture to talk about. I hope you realize how amazing that is that oxygen comes out of this process and we're so freaking lucky. 100% we would not be here if that were not the case. So somehow we're fixing carbon. Two stages of this process. The first stage is relies on light. So we'll do it like this. Couldn't decide my color. Just so many options. The light reactions are how we get light energy and basically we take light energy and turn it into energy, not glucose. We turn it into ATP and high energy, electron carriers, and I gotta draw some wheels on those things. True story. That's step one. We capture the light energy. Then we've got chemical energy and it goes into another cycle. It goes into this cycle. Oh man, this drawing is the worst drawing I've ever done ever. So forgive me. You can imagine that taking carbon dioxide out of the air and turning it into sugar is gonna cost energy. In the form of ATP and high energy, electron carriers, folks we know well. Where do we get those guys from energy from the sun? And that's how sunlight fuels the production of glucose. It's pretty phenomenal. That is the big picture. Okay, never mind. I thought I was done. But I'm gonna tell you this. We have the light reactions that produce ATP and high energy electron carriers. There are two pieces and they're photosystems. Photosystems two and one. And they're in that order on purpose. I'm not gonna tell you what photosystems are because that's the next two sections because I'm gonna spend a section on each photosystem. And then this carbon dioxide turning into glucose. This is called the Calvin cycle. The Calvin cycle is named after a dude named Melvin Calvin. And yes, I want to have a cat or a duck so that I can name them Melvin Calvin. Melvin Calvin get off the couch. That goes for a duck and a cat. Most of our things that are named after humans anymore are being changed. Citric acid cycle used to be named after homeboy Krebs. Don't know, can't remember what Krebs' first name is because I practiced, practiced to avoid calling the citric acid cycle the Krebs cycle, but it's the same thing. Calvin cycle doesn't have another name that eliminates the human out of the name yet that I know of. So mark this, it is May 3rd, 2023. Somebody I'm sure will holler at me if there is a name other than Calvin cycle for that process. Okay, you're with me. We're going to talk about the light reactions both photosystems next.