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Cell Biology

Learn the toughest concepts covered in Cell Biology with step-by-step video tutorials and practice problems by world-class tutors

22. Techniques in Cell Biology

Electron Microscopy



Electron Microscopy

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Hi in this video, I'm gonna be talking about electron microscopy. So electron microscopy uses electrons to visualize cells. Now the reason electrons are kind of a better way or a more precise way than light microscopy is because electrons microscopy gives a much higher limit of resolution. This is up 2.2 nanometers in case you're keeping track, that's 100 times 100,000 times greater than a light microscope. So much better. Now this is in theory it's 100 times greater in practice because of just error and different nuances of the technique. You rarely if ever get 100,000 greater magnification a 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, it's so you can see such, you know, has such a high or low limited 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 1-200 thickness of a cell in order to visualize the sample using electron microscope. And also we need to process the samples so that electrons can be used to visualize them. So there's 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. The ones you'll come across in your book. But the first one is the gold staining. 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. And so um through the electron microscope. So that allows you to you know, for instance use gold antibody to label certain proteins or certain organelles. And then you can very clearly see them because they're labeled as black in this scope. Another one is through metal shadowing and 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 you know, get a rock for instance something with jagged edges. And you are too just like spray paint it. That spray paint would be darker in some areas and lighter and others because all of those edges on that rock um prevent the paint from getting um 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 across and you just coat it with a little bit of metal at one angle, you're going to get the shadowing effect where some of it got more and some of it got left less. And so you create these shadows that can then be used to look at the structure or really get a good image of that structure of that angle of the specimen you're looking at Now, there are two 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 electron through the sample. So this is kind of like the light microscope where you shoot a light just directly straight through the sample transmission. You you shoot it directly through the sample. And this differs from scanning electron microscopy because scanning electron microscopy is very much like a scanner. Right? So you just sort of scan the electrons on the specimen surface and that 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 in electron microscopy image. This is a mitochondria. So these are extremely tall 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 you can see these fine structures these membranes, you can see actually the to the double membrane here, the outer membrane and the inner membrane if you look really close with mitochondria. So electron microscopy really gets you very specific images and can look at much um much more refined detail than light microscopy. So with that, let's now move on.

Light microscopy has an improved limit of resolution compared to electron microscopy.


Which of the following types of microscopy works by shooting electrons through the specimen?