Hi. In this video, I'm going to be talking about electron microscopy. So electron microscopy uses electrons to visualize cells. Now the reason electrons are a kind of better or more precise way than light microscopy is because electron microscopy gives a much higher limit of resolution. This is up to 0.002 nanometers. In case you're keeping track, that's a 100 times 100,000 times greater than a light microscope, so much better. Now, this is in theory; it's a 100 times greater in practice because of just error and different nuances of the technique. You rarely, if ever, get a 100,000 times greater magnification or resolution than the light microscope, but it is possible. And so it's much better and more specific. You can see a lot more. But because it's more specific and can see such a high or low limit of resolution, that means that the samples have to be really processed correctly. So the specimens have to be preserved, and they have to be cut extremely thin. This is 1 to 200th the thickness of a cell in order to visualize a sample using an electron microscope. And also, we need to process the sample so that electrons can be used to visualize them. So there are a couple of ways of doing this. There's more than I'm mentioning, but I'm kind of just mentioning the ones that are most mostly used and the ones you'll come across in your book.
But the first one is immuno-gold staining. And so immuno-gold staining is responsible for labeling specimens with gold. So you put just this very thin layer of gold on it, and the reason you do this is because it's very electron dense. And so that way when you shoot electrons at the sample, that electron-dense area is going to appear as black through the electron microscope. So that allows you to, for instance, use a gold antibody to label certain proteins or certain organelles, and then you can very clearly see them because they are labeled as black in this scope. Another one is through metal shadowing. This is where you coat the specimen with some type of metal, but you only do it instead of gold staining, which is staining the whole thing. Metal shadowing only uses one angle. And you can imagine that if you were to get a rock, for instance, something with jagged edges, and you were to just like spray paint it, that spray paint would be darker in some areas and lighter in others because all of those edges on that rock prevent the paint from getting every single place. And so it creates those shadows of paint. The same thing is with the molecules in the cell. So if you take a sample that's going to be used for electron microscopy and you just coat it with a little bit of metal at one angle, you're going to get this shadowing effect where some of it got more and some of it got less. And so you create these shadows that can then be used to look at the structure, or like really get a good image of that structure, that angle, of the specimen you're looking at.
Now, there are 2 main types of electron microscopy, and they differ based on how they shoot electrons across or through a sample. So the first one is transmission electron microscopy, and this shoots electrons through the sample. So this is kind of like the light microscope where you shoot light directly straight through the sample. Transmission, you shoot it directly through the sample. This differs from scanning electron microscopy in that it allows for much finer details at that surface that you're looking at versus just shooting it all the way through.
So here is an example of an electron microscopy image. This is a mitochondrion. So these are extremely detailed mitochondria, but you can see these internal structures using electron microscopy. And to be honest, this is actually an older image. The technology today would get much better images than what I'm showing you here. But you can see these fine structures, these membranes. You can see actually the two, the double membrane here, the outer membrane and the inner membrane, if you look really close, in mitochondria. So electron microscopy really gets you very specific images and can look at much, much more fine detail than light microscopy. So with that, let's now move on.
