In this video, we're going to talk about chloroplast structure. And so very similarly to mitochondria, chloroplasts actually have 2 membranes. They have an outer membrane and they have an inner membrane as well. But unlike mitochondria, neither of the chloroplast membranes have folds or cristae. And recall from our previous lesson videos that mitochondria have folds or cristae in the inner mitochondrial membrane.
But once again, the chloroplast membranes, neither of them have folds or cristae. And so if we take a look at our image down below, notice the left hand side of our image is showing the same light microscope image from our last lesson video zooming into plant cells, and all of these green circles that we see here represent chloroplasts. And so if we zoom into one of these green circles, it'll look something like this, what we're showing you here. And so the first thing to note about the chloroplast that we're showing you here is that it has 2 membranes. It has an outer membrane that we're labeling, right here on the outside, and then it has an inner membrane as well that's on the inside.
But notice that neither the outer membrane nor the inner membrane has folds or cristae. They don't have folds or cristae. Now, you'll also notice that inside of the chloroplast, there are these other structures, and one of the things that you'll notice right away are these green pancake-looking structures that are all over the place on the inside. And these green pancake-looking structures are called thylakoids. And so thylakoids are interconnected pancake-shaped sacs that are within the chloroplast, and they're very important for a part of the photosynthesis reaction.
Now, you'll also notice that the thylakoids, each of these individual green pancake-looking structures are forming stacks, and these stacks of the thylakoids are referred to as grana, and that is the plural form here. So grana are referring to stacks of thylakoids, or in other words, stacks of the green pancakes or green pancake stacks, if you will. Now remember, these green looking pancakes, they're not actually pancakes. Of course, they're called thylakoids. And the space, the innermost region of the chloroplast is specifically referred to as the stroma.
And so the stroma is pretty much equivalent to the matrix of the mitochondria. And so it's the innermost region of the chloroplast that contains enzymes, ribosomes, and chloroplast DNA as well. And so down below in our image, notice that we're saying that the stroma, well, it's just the innermost region here. It's basically the space that fills the, I'm sorry, the chloroplast here on the innermost region here. And so this here concludes our introduction to chloroplast structure, and we'll be able to get some practice applying these concepts as we move forward in our course.
So I'll see you all in our next video.