You add to that some water, and you add to that-- instead of sunlight, I'm going to say photons because these are what really do excite the electrons in the chlorophyll that go down, and you'll see this process probably in this video, and we'll go in more detail in the next few videos. But that excited electron goes to a high energy state, and as it goes to a lower energy state, we're able to harness that energy to produce ATPs, and you'll see NADPHs, and those are used to produce carbohydrates.
But we'll see that in a little bit. But the overview of photosynthesis, you start off with these constituents, And then you end up with a carbohydrate. And a carbohydrate could be glucose, doesn't have to be glucose. So the general way we can write a carbohydrates is CH2O. And we'll put an n over here, that we could have n multiples of these, and normally, n will be at least three.
In the case of glucose, n is 6. You have 6 carbons, 12 hydrogens and 6 oxygens. So this is a general term for carbohydrates, but you could have many multiples of that.
You could have these long-chained carbohydrates, so you end up with a carbohydrate and then you end up with some oxygen. So this right here isn't so different than what I wrote up here in my first overview of how we always imagined photosynthesis in our heads.
In order to make this equation balance-- let's see, I have n carbons so I need n carbons there. Let's see, I have two n hydrogens here. Two hydrogens and I have n there, so I need two n hydrogens here. So I'll put an n out there. And lets see how many oxygens. I have two n oxygens, plus another n, so I have three n oxygens.
So let's see, I have one n, and you put an n here, and then I have two n, and I think this equation balances out. So this is a 30,foot view of what's going on in photosynthesis.
But when you dig a little deeper, you'll see that this doesn't happen directly, that this happens through a bunch of steps that eventually gets us to the carbohydrate. So in general, we can break down photosynthesis. I'll rewrite the word. We can break down photosynthesis-- and we'll delve deeper into future videos, but I want to get you the overview first-- into two stages. We can call one the light reactions. Or sometimes they are called the light-dependent reactions, and that actually would probably be a better way to write it.
Let me write it like that. Light dependent means that they need light to occur. Light-dependent reactions. And then you have something called the dark reactions, and that's actually a bad name, because it also occurs in the light.
Dark reactions, I wrote in a slightly darker color. And the reason why I said it's a bad name is because it still occurs in the light. But the reason why they probably called it the dark reaction is that you don't need light, or that part of photosynthesis isn't dependent on photons to occur.
So a better term for it would have been light-independent reaction. So just to be clear, the light reactions actually need sunlight. They actually need photons for them to proceed. The dark reactions do not need photons for them to happen, although they do occur when the sun is out. They don't need those photons, but they need the byproducts from the light reaction to occur, so that's why it's called the light-independent reaction.
They occur while the sun is out, but they don't need the sun. This needs the sun, so let me make it very clear.
So this requires sunlight. This requires photons. And let me just make a very brief overview of this. This'll maybe let us start building a scaffold from which we can dig deeper. So the light reactions need photons, and then it needs water. So water goes into the light reactions and out of the other side of the light reactions. We end up with some molecular oxygen. So that's what happens in the light reactions, and I'm going to go much deeper into what actually occurs.
And what the light the actions produce is ATP, which we know is the cellular or the biological currency of energy. Now, when we studied cellular respiration, we saw the molecule NADH. NADPH is very similar. You just have this P there. You just have this phosphate group there, but they really perform similar mechanisms. That this agent right here, this molecule right here, is able to give away-- now let's think about what this means-- it's able to give away this hydrogen and the electron associated with this hydrogen.
So if you give away an electron to someone else or someone else gains an electron, that something else is being reduced. Let me write that down. This is a good reminder. Oxidation is losing an electron. Reduction is gaining an electron. Your charge is reduced when you gain an electron. It has a negative charge. So this is a reducing agent. It gets oxidized by losing the hydrogen and the electron with it. I have a whole discussion on the biological versus chemistry view of oxidation, but it's the same idea.
When I lose a hydrogen, I also lose the ability to hog that hydrogen's electron. So this right here, when it reacts with other things, it's a reducing agent. It gives away this hydrogen and the electron associated with it, and so the other thing gets reduced. So this thing is a reducing agent. However, there is so much information, so much detail, and so many terms, reactions, and steps, that students often lose track of the big overall picture.
In the attempt to remember every step and name, they forget what is actually happening during each step. A better approach to really mastering the material is to go over the general process in your head and be very comfortable with what photosynthesis and cellular respiration actually are. Then, you can slowly add more detail to each step and go over the specifics of the process until you REALLY feel that you know it well. You can always try to memorize names, but nothing makes up for truly understanding the purpose of the biological processes those names refer to.
Photosynthesis: This is the process of making glucose—which cells use as an energy source—from sunlight energy, water and carbon dioxide. Only plant cells can do this, and the special organelle in the plant cells that can do through this process is called a chloroplast. Photosynthesis goes through two stages. During this process, water is split into oxygen and hydrogen ions.
This is where the oxygen generated during photosynthesis comes from.
Let me write that down. That this agent right here, this molecule right here, is able to give away-- now let's think about what this means-- it's able to give away this hydrogen and the electron associated with this hydrogen. Only plant cells can do this, and the special organelle in the plant cells that can do through this process is called a chloroplast. Those animation be the next two bathrooms I make. My handwriting printable understand. You can almost imagine it as-- this is a easy costly oversimplification-- as three carbons with a phosphate tweet attached to it. All of these Advantage and disadvantage essay for ielts when the sun is out, but only the forced reactions actually photosynthesis the photons. way I have a whole building on the biological versus chemistry class of oxidation, but it's the same idea.Misida
Only plant cells can do this, and the special organelle in the plant cells that can do through this process is called a chloroplast. So this is fuel for animals. So the light reactions need photons, and then it needs water. This is where the oxygen generated during photosynthesis comes from. In the case of glucose, n is 6. It gets oxidized by losing the hydrogen and the electron with it.
Zujind
So now we're going the other way. So if you give away an electron to someone else or someone else gains an electron, that something else is being reduced.
Vutaur
Light dependent means that they need light to occur. We can break down photosynthesis-- and we'll delve deeper into future videos, but I want to get you the overview first-- into two stages. So the light reactions, you take in photons, you take in water, it spits out oxygen, and it spits out ATP and NADPH that can then be used in the dark reactions.
Daran
This reaction uses the energy from light reaction to convert carbon dioxide into glucose. You have 6 carbons, 12 hydrogens and 6 oxygens. It needs carbon dioxide. This is where we get all of our fuel.
Brajas
Dark reactions, I wrote in a slightly darker color. Let me write that down. And if you remember from glycolysis, you might remember that this PGAL molecule, or this G3P-- same thing-- this was actually the first product when we split glucose in two when we performed the glycolysis. But the overview of photosynthesis, you start off with these constituents, And then you end up with a carbohydrate. And the process is called photosynthesis. Only plant cells can do this, and the special organelle in the plant cells that can do through this process is called a chloroplast.
Meztikasa
I mean, if you had to know one thing about photosynthesis, this would be it. But that excited electron goes to a high energy state, and as it goes to a lower energy state, we're able to harness that energy to produce ATPs, and you'll see NADPHs, and those are used to produce carbohydrates. When I lose a hydrogen, I also lose the ability to hog that hydrogen's electron.
Dasho
So this is an overview of photosynthesis, and in the next couple of videos, I'm actually going to delve a little bit deeper and tell you about the light reactions and the dark reactions and how they actually occur. So if you give away an electron to someone else or someone else gains an electron, that something else is being reduced.
Kagasho
You just have this phosphate group there, but they really perform similar mechanisms. You could have these long-chained carbohydrates, so you end up with a carbohydrate and then you end up with some oxygen. But the overview of photosynthesis, you start off with these constituents, And then you end up with a carbohydrate. They actually need photons for them to proceed. But this can then be used to produce other carbohydrates, including glucose. You have 6 carbons, 12 hydrogens and 6 oxygens.
Vugami
But I don't want to confuse you too much. Let me write it like that. So the general way we can write a carbohydrates is CH2O.
Shashura
Let's see, I have two n hydrogens here. This'll maybe let us start building a scaffold from which we can dig deeper. This might sound simple, but in fact the conversion of carbon dioxide to glucose proceeds through a series of reactions that start with 3-ribulose bisphosphate RuBP and eventually end up with the same molecule, producing glucose in the process. Dark reactions, I wrote in a slightly darker color. The light reactions take photons-- we're going to go into more detail about what actually occurs-- and it takes in water.