In this video we're going to begin our lesson on microscopes. And so a microscope as its name implies with the root micro and the root scope is really just an optical scope that can be used to visualize really really small or in other words microscopically small objects. For example, cells which we know are the smallest unit of life. Now recall that the root micro is a root that means small and also the scope is really just an object that we look through with our eyes and so we can look through a microscope in order to visualize these really really tiny or microscopically small objects. Now really there are 2 main types of microscopes that are commonly used that you should be familiar with and so notice that we have these two main types of microscopes numbered down below number 1 and number 2 And so the first main type of microscope that you should be familiar with are the light microscopes and as their name implies these light are going to be using visible light in order to magnify small objects and make those objects appear larger. Now these light microscopes are very common and they're very prevalent and so these light microscopes are the ones that you are most likely going to be using in any typical biology lab. Now the electron microscopes on the other hand are the 2nd main type of microscope and unlike the light microscopes which use visible light to magnify small objects electron microscopes do not use visible light instead electron microscopes as their name implies they're going to be using electrons in order to provide an even higher magnification of small objects allowing us to see even smaller objects than what the light microscope is capable of allowing us to see. And so these electron microscopes are significantly more advanced and more complex and more expensive tools in comparison to the light microscopes and so it's much less likely that you get to use an electron microscope simply because of how expensive they can be, but it is possible to be able to use them, in some labs. And so if we take a look at our image down below we'll be able to see an example that shows the ranges of the human eye, light microscopes, and electron microscopes as well. And so what you'll notice is that in this image it's really showing you a scale that goes from left to right and this scale is organizing these different objects in terms of their size. Where the smallest objects are on the far left over here, so we can put small over here, and the largest objects are over on the far right. So we can put large on the far right and so notice that the largest object that we're showing here is actually a human being like me and you and, notice that the smallest object being shown is actually the atom. And so, notice that the atom is being measured in these units, here it says 1 and it has this a with a little circle on top. That's a unit called an angstrom that which, we'll get to talk more about later in our course, but angstroms are basically just really really really small units. Okay? So, atoms are very very small and as you go towards the right of our scale the objects get larger and larger and larger and notice that we're measuring in units of meters over here. And so one thing to note here is that, down below what we have is the range of the human eye in this green scale. So notice that the human eye has a cut off in terms of how small, of objects it's capable of seeing. So notice that the human eye, is not capable of seeing most plant and animal cells and you know most bacteria and archaea. Those are too small to be seen by our human eyes. And so in order to see all of these microscopically small objects, we need to be able to use microscopes. And so notice that here in this blue range, what we have is the range of the light microscope and again the light microscope is going to be using visible light in order to magnify small objects and make those objects appear larger. So the light microscopes can be used to visualize most, cells, most plant and animal cells as well as most bacteria and archaea and so these light microscopes are very common and again these are the types of microscopes that you're most likely going to use in your biology labs, but you'll notice that these light microscopes, although they are very useful, they also have a cut off and so they're not able to visualize all of these other small objects like viruses and molecules like what you see down below and atoms. And so in order to visualize some of these we need a more powerful, a more advanced type of microscope and this is where the electron microscope comes into play. So this orange bar here is showing you the range of the electron microscope. And so notice that the electron microscope allows us to visualize most plant and animal cells as well as most bacteria and archaea, but it also allows us to visualize very very very small objects such as viruses, proteins and lipids, and very very small molecules approaching down to individual atoms. And so, what you'll notice here in this image is that the plant and animal cells which we know from our previous lesson videos are eukaryotic cells that have a nucleus, They are larger than most bacteria and archaea which are prokaryotic cells. So that's an important learning objective and something important to note from this image. And so this here concludes our brief introduction to microscopes and we'll be able to apply these concepts as we move forward and learn more as well. So I'll see you all in our next video.
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Types of Electron Microscopes
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Video transcript
So now that we know that electron microscopes are very powerful magnifying tools, in this video we're going to talk about some different types of electron microscopes. And so really there are 2 main types of electron microscopes that you all should know that are used to study both external and internal cell structures. And so we've got these 2 electron microscope shown down below. The first is going to be the scanning electron microscope or the SEM for short. And so the scanning electron microscope or the SEM is specifically used to visualize external cell surfaces and structures on the outside surface of cells. Now, the second type of microscope that you all should know is the transmission electron microscope or the TEM for short. And so the transmission electron microscope or TEM is specifically used to visualize internal cell structures and organelles. So let's take a look at our image down below to better get a better understanding of this. Notice on the left hand side over here, we have this really fancy piece of equipment, and this piece of equipment here is a scanning electron microscope. It's a very, very fancy and a very, very expensive microscope that's used to visualize external cell structures. And so you should know that SEMs are used to visualize external cell structures on the surface of cells. And then over here on the right hand side of the image, we have another fancy piece of equipment. And this fancy piece of equipment here is a transmission electron microscope or a TEM, another incredibly expensive piece of equipment that's used to visualize, as this image shows over here, internal structures and organelles within cells. And so moving forward, we're going to be talking about lots of different cell structures, and it's important to know that, scientists can actually visualize these cell structures using either SEMs, if it's external cell structures, or TEMs if they are internal cell structures. So this here concludes our introduction to the different types of electron microscopes, and we'll be able to get some practice applying these concepts in our next video. So I'll see you all there.
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Problem
Problem
What type of microscope would a researcher use to measure the size of a ribosome inside a eukaryotic cell?