9. Photosynthesis
Stages of Photosynthesis
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In this video, we're going to briefly introduce the stages of photosynthesis. And so photosynthesis actually occurs in 2 stages that we have numbered down below. And so the first stage of photosynthesis is the light reactions, And the second stage of photosynthesis is the Calvin cycle. And so moving forward in our course, we're going to talk a lot more details about both the light reactions and the Calvin cycle as well. But here in this video we're just introducing these 2 stages. And so the light reactions as their name implies is going to convert light or photons and water into chemical energy and oxygen gas. And the Calvin cycle is going to use carbon dioxide from the atmosphere as well as the chemical energy that was formed by the light reactions in order to synthesize glucose, the sugar. And so down below in our image we can see the stages of photosynthesis, and we know that the chloroplast acts as the site of photosynthesis. And so notice that in the background here in green what we're showing you is the chloroplast, the site of photosynthesis. But inside of the chloroplast, photosynthesis is broken up into 2 stages. The first stage are the light reactions, which occur inside of the thylakoids. And again we'll talk a lot more about the light reactions as we move forward in our course. And then the second stage of photosynthesis are the Calvin Cycle reactions which are going to occur in the stroma of the chloroplast. And so what you can see here is when, with the light reactions, which is the first stage of photosynthesis, it uses light, it uses photons of light from the sun, and it also uses water. And so these 2 reactants come in and what comes out are, is oxygen gas and chemical energy that's used to power the Calvin cycle. And so that's basically what we've described here for the light reactions. Now for the Calvin cycle, notice that it's going to use carbon dioxide from the atmosphere along with chemical energy that was produced by the light reactions, and it's gonna use both of those to generate glucose. And so, ultimately, what you can see is that coming into the chloroplast is, solar energy, water, and carbon dioxide. These are things that all come into the chloroplast. And the things that come out of the chloroplast are oxygen gas and glucose, and so those are the products of photosynthesis as we've discussed them, in our previous videos. And so again, we're gonna talk a lot more about each of these stages of photosynthesis, the light reaction and the Calvin cycle as we move forward in our course. But for now this here concludes our brief introduction to the two stages of photosynthesis, and I'll see you all in our next video.
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