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