Photosynthesis vs. Cellular Respiration

Jason Amores Sumpter
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in this video, we're going to compare and contrast photosynthesis versus cellular respiration. And so what you may have noticed is that photosynthesis and cellular respiration seem kind of similar when you compare their chemical equations. And so it turns out that photosynthesis and cellular respiration are both very ancient pathways that have been around for billions of years, and they're actually really highly connected to one another. And this is because each process produces the reactant that are necessary for the other process. And so, for example, photosynthesis produces products that are used as the reactions for cellular respiration, and cellular respiration produces products that are used as the reactant for photosynthesis. And so we'll be able to see this down below in our image. And also, it turns out that photosynthesis and cellular respiration are almost exactly the opposite of each other in terms of their overall chemical equations, and we'll be able to see that down below in our image as well. And so, in our example, we're gonna be looking at the connection between cellular respiration and photosynthesis. And so taking a look at this top half of the image up here, notice that it's occurring inside of the chloroplasts organelles. And so this is, of course, the chemical equation for photosynthesis that we recently talked about in our last lesson video. And so, of course, photosynthesis is going to take carbon dioxide water and sunlight energy from the atmosphere and convert those things into sugars such as glucose and oxygen gas as a by product. But what you'll notice is that the products here of photosynthesis, which are glucose and oxygen, are actually used by mitochondria. And so you'll notice that glucose and oxygen here are being used by the mitochondria. And one thing to note about this image here of the mitochondria is that it's actually flipped around. Eso that the reactant air here on the right and the arrow notices going from right toe left here. So these over here are the products of what is known as cellular respiration, which we already covered in our previous lesson videos. And so what you'll notice is that the reactant is here of the mitochondria of cellular respiration. Um, are the products of photosynthesis, and you'll see that cellular respiration converts oxygen and glucose and converts them into the products of carbon dioxide, water and a lot of a teepee energy. And so what you'll notice here is that carbon dioxide and water are products of cellular respiration, but they're actually used as the reactant for photo synthesis. And so you can see how the, uh, each process is going to produce the reactant that air needed for the other process. Now, you can also see that these two equations the equations for photosynthesis and the equation for cellular respiration are almost exactly opposites of each other. And so the reason for that is because notice that carbon dioxide, water and energy are all reactant for photosynthesis, whereas carbon dioxide, water and energy are all products for cellular respiration. Remember their products because the arrows going from right toe left here and which will also notice, is that in photosynthesis, glucose and oxygen, our products for photosynthesis. But glucose and oxygen are reacting. It's for cellular respiration. And so, really, when you compare these two equations side by side, they do line up really, really similarly and really, the Onley difference where they don't line up so similarly is the type of energy that's used or produced cellular respiration is gonna be producing ATP, whereas photosynthesis is you using solar energy or sunlight energy. And so another thing that you'll notice is that, uh, the substances in terms of being oxidized or reduced our flip as well. And so notice that in photosynthesis carbon dioxide is being reduced to glucose. But notice down below. In cellular respiration, glucose is being oxidized to carbon dioxide. So there's the flip there and then also in photosynthesis, water is being oxidized to oxygen, whereas down below in cellular respiration, oxygen is being reduced to water. And so they are reverse in that respect. And so one thing that helps me remember how which substances are oxidized and reduced is that I know that photosynthesis is going to be synthesizing something and that is, God going to be a glucose molecule. Glucose is going to be synthesized. It's gonna be synthesized using carbon dioxide. It's literally able to take carbon dioxide gas from the atmosphere and use that carbon dioxide gas to build a glucose. And glucose has a lot more chemical bonds in it than carbon dioxide. And so these chemical bonds are gonna be made using electrons, and so carbon dioxide is gonna need to gain Ah, lot of electrons, or it's gonna need to be reduced in order to be used to create glucose. So this helps me remember that carbon dioxide has to be reduced. It has to gain a lot of electrons for it to make all of the chemical bonds that are found in glucose and, uh, ultimately water eyes going to be oxidized. That means that water is going to be losing electrons and being used to produce oxygen now in cellular respiration. I know that glucose has a lot of chemical bonds in it and glucose because it has a lot of chemical bonds in it. It needs to be broken down. It needs to be stripped of electrons. It needs to lose electrons, and when it loses electrons, it's going to be converted into carbon dioxide. And ultimately, the oxygen here we know is gonna act as the final electron, except er in cellular respiration. And so the oxygen, because it's acting as the final electron, except er, it's going to be gaining the electrons or it's going to be reduced and be converted into water. And so those are some ways to help you remember that photosynthesis and cellular respiration are very similar to each other, almost exact opposites. And once again, the only difference is that there is sunlight, energy here but down below. There's a teepee energy here, and other than that, they are pretty much exactly the opposite of each other. Now this here concludes our comparison of photosynthesis and cellular respiration, and we'll be able to get some practice as we move forward in our course. And we'll also continue to talk more and more about photosynthesis, so I'll see you all in our next video.
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