in this video, we're going to begin our lesson on electron microscopes. And so recall from our previous lesson videos that electron microscopes, as their name implies are going to use electrons instead of using light. And these electron microscopes are much more powerful tools than the light microscopes themselves. And this is because electron microscopes actually provide greater magnification. In fact they can provide magnification up to million times magnification, which means that they can make objects appear 10 million times larger than the actual object is. And this is in comparison to just the 1000 X magnification provided and most standard light microscopes now electron microscopes, not only do they provide greater magnification, they also provide greater resolution As well. In fact, electron microscopes can provide resolution up to about 0.3 nm, which is incredibly great resolution. And this is in comparison to the 10 nanometer resolution provided even in a super resolution microscope. And so the light microscopes in general are not able to provide as high of a magnification or as great of a resolution as the electron microscopes are capable of providing. Now these electron microscopes because they are such powerful tools. They're really, really complex instruments and it usually requires complex specimen preparation as well that ultimately limits the observation to only non living cells and objects. And so it's very difficult to be able to visualize living cells with electron microscopes because a lot of times the sample preparation will ultimately end up killing the cells. Now the electron micro grafts or the images created by these electron microscopes are usually going to be just black and white, but they can be falsely colored uh in order to create images that have color in them. And so the false color is usually done by specialized computers. And so if you take a look at this image down below notice, it's showing you a little map of the electron microscopes and, really, as well, see moving forward, there are two main types of electron microscopes that will talk about and those are the transmission electron microscope, or the t e M, as well as the scanning electron microscope or the s e. M. And so we'll start off talking about the transmission electron microscope and then later in a different video, we'll talk about the scanning electron microscope. So I'll see you all in our next video.
Transmission Electron Microscope (TEM)
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In this video, we're going to briefly introduce transmission electron microscopes, or T E. M. S. And so transmission electron microscopes are commonly abbreviated as T E. M. S. And these are microscopes that form a two D. Image or a two dimensional image from a beam of electrons passing through a specimen. Now there are a variety of sample preparations that can be used to prepare a specimen for visualization under a transmission electron microscope. But many of these sample preparations are going to be used for visualizing internal cell structures. And so usually you want to associate the transmission to make electron microscope or the TM with the visualisation of internal cell structures. Now, these specimens that are being visualized under a T. E. M must be viewed in a vacuum and they have to be an extremely thin slices of just 20 to 100 nanometers. And so what that means is that there is some complex specimen preparation that's needed to be done before they can be visualized under transmission electron microscope. Now, what are the drawbacks is that sometimes this complex sample preparation can actually distort the cells and cause artificial artifacts to form? And so these artificial artifacts are really just going to be substances that are usually not inside of the cells. But after this complex sample preparation, they are introduced into the cells. And so experienced scientists that know how to use transmission electron microscopes need to be trained to be able to identify these artificial artifacts so that they don't confuse them with actual cell structures. And so down below, we're showing you a diagram of the transmission electron microscope, which which is once again abbreviated as just the T. E. M. And so notice over here, on the left hand side, we're showing you an actual image of a transmission electron microscope, which is a very fancy and expensive piece of equipment that's hooked up to uh this computer here and over here, what we have is a little diagram of this tm. And so which will notice is that the very very top there is an electron gun which is going to shoot a beam of electrons. And so we have our electron beam here is in pink. And so the electron beam is going to pass through a condenser lens and then it will pass through the actual specimen. And so notice that the placement of the specimen is right here towards the middle. And then the electron beams are going to essentially pass through an objective lens and a projector lens and ultimately onto a viewing screen to create the image. And then the viewing I. P. S. Can be used to visualize that image. And so these are some of the images that can be created by a transmission electron micrografx. And so notice here that we're showing you some green algae cells. Now notice that the image itself is not green because electron microscopes generate black and white images naturally and they can be falsely colored. Using a computer here, we're showing you some avian coronavirus here, we're showing you the mitochondria and a human lung cell. And over here what we're showing you is the Ebola virus. And so these transmission electron microscopes and electron microscopes in general are powerful enough to actually visualize viruses. Whereas light microscopes are generally not powerful enough to visualize microscope to visualize viruses in this way right here. And so once again, one of the main features you want to remember about the transmission electron microscope is that it can be used to visualize internal cell structures. And so this year concludes our brief introduction to the transmission electron microscope and we'll be able to get some practice applying these concepts as we move forward. So, I'll see you all in our next video
Electron microscopes differ from light microscopes in that:
Electron microscopes use an electron beam instead of a light beam.
Electron microscopes can magnify the specimen significantly more than light microscopes.
Electron microscopes have significantly higher resolution than light microscopes.
All of the above.
Scanning Electron Microscope (SEM)
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In this video, we're going to begin our lesson on the scanning electron microscope or the S. E. M. And so the scanning electron microscope is commonly abbreviated as the S. E. M. And this is a microscope that will actually form a three D. Image or a three dimensional image. Unlike the T. E. M. The transmission electron microscope, which recall only forms two D. Images or two dimensional images. And so the ECM forms three D images from a beam of electron scattering off of a specimen surface. And so there are a variety of sample preparations that may be used for a scanning electron microscope, but they're mainly used for visualizing external cell structures on the surface of the specimen. And so if we take a look at this image down below, it's showing you a diagram of the scanning electron microscope or the S. E. M. And so notice over here on the left hand side, we're showing you an actual image of a scanning electron microscope, which is once again a very complex uh instrument and a very expensive instrument that is hooked up to a computer. And so over here we're showing you a little diagram of the scanning electron microscope. And so once again, there is an electron gun at the top, which is going to create an electron beam here, which is the uh, with the pink lines represent. And the electron beam is gonna pass through an electromagnetic lenses and uh, it's going to ultimately hit the actual specimen itself. So notice the specimens placement is different than that of the transmission electron microscope, and notice that the electrons are actually scattering off of the surface of the specimen. And so the scattered electrons can be detected by an electron collector. There's an amplifier in place and that ultimately projects the the image onto a viewing screen. And these are some of the images that can be captured by a scanning electron microscope, which again, is going to be important for visualizing external cell structures instead of internal cell structures, like the transmission electron microscope is used for. And so here is an image of some melting ice, an image of prairie holly hawk, pollen, algae, and bacterial cells and the surface of a butterfly wing. And so notice that all of these images are three dimensional and focused on observing external cell structures. And so this year concludes our brief introduction to the scanning electron microscope or the ECM, and we'll be able to get some practice applying these concepts as we move forward. So I'll see you all in our next video.
There are two major types of electron microscopes, Transmission Electron Microscopes (TEM) & Scanning Electron Microscopes (SEM). What are the major differences between these types of electron microscopes?
TEM shows 2D images of the specimen while SEM shows 3D images of the specimen.
SEM specimen preparations can damage or distort the microorganism’s features, while TEM preparations do not.
TEM shows internal cell structures, while SEM show external cell structures.