okay welcome back and now we're going to talk about microscopy and some of the common components of cells and why cells are small in this lecture okay so the two [Music] types of microscopy that we will talk about in this class and that i want you to be able to recognize images of is the light microscopy and this is the type you've done used in school before so uses light to eliminate whatever you have on your slide under here um pretty simple basic type of microscope it's also called bright field so you may hear either term and remember that the whole reason we use microscopes is because cells are so small we can't see them very well without a microscope so i want you to understand these two different types of microscopes and what you can actually see with them and what you can't the second type we'll talk about is the electron microscope and it's this amazingly huge uh complex microscope that actually uses electrons to create the image versus light to create the image and we're going to talk about two different types of electron microscopy transmission and scanning note that only with light microscopy can you look at live cells everything that you see under an electron microscope will be dead we have to fix the cells so that we can shoot those electrons through them to get the image okay so light microscopy you can see cells but only really a few organelles nothing much smaller so you've seen this picture already here where we're looking at a cheek cell and you can see the little bacterial cells on it and the organelle you can see here you can see this dark staining that represents the nucleus this is a dead cell because it has been stained so if you i never get phone calls there we go okay um because it has been stained the stain kills the cells we have to fix the cells okay so here are some bacteria that have also been stained so note that most cells are see-through they're they don't have color to them this is a lovely paramecium this is a protist single-celled organism and you can kind of see you can kind of like look right through it it's it's see-through so a lot of times we have to fix the cells and stain them so that we can really see them well under the microscope um these would be live plant cells and all these green little circles those are your chloroplasts we'll talk about chloroplasts in a little bit and these are naturally green so they give the plant color that you see on the trees and bushes and you can also see these organelles excuse me under the light microscope so a very few organelles you can actually distinguish under the microscope in the perimysium it has some food vacuoles and things that you can kind of see we'll look at this a little bit more but it also has cilia but really with light microscopy you're looking at cells you're looking at cell shape you can stain them and they'd be dead cells and you can see a little bit more detail but you're not going to be able to see the er the golgi some of the other organelles that we're going to talk about again this is just showing you here's an amoeba in its natural beauty and here is a stained amoeba so these would be dead they're stained pink amoebas aren't naturally pink so with light microscopy you can see both live and dead if you want to see what cells look like live moving um you can check out this video um i put super long but super cool so obviously you don't have to watch it all but um it's pretty fun to watch different cells move around so if you're wondering why i look over here i'm checking my notes to make sure i've covered everything i want to cover for each slide um a type of microscopy that we're not going to really talk about but you've probably seen images of it is the use of fluorescence so there are proteins that fluoresce naturally a protein called green fluorescent protein we can also use antibody staining for fluorescence so some of these amazing images these are all dead cells to stain them we have to um kill them um unless they have gfp and now i'm making things more complicated but i just wanted to tell you if you see these types of images this is fluorescence this is with another special type of microscope and if you take cell biology with me you'll learn more about fluorescence okay and then the electron microscope this is giving us these amazing details so we have transmission electron microscopy and what's happening is you're seeing internal structures the electrons are transmitting right on through the cell so with tem it's really a 2d like a flat image it's the um it's the what do i want to say the internal structures and i should write this word transmission okay so it's just a nice um think of it as a flat view but so many details i mean look down here now you see the nucleus the nucleolus you can clearly see mitochondria vacuoles this these two right here are what we call false colored because electron microscopy electron micrographs so micrograph means the image you get from microsoft they're black and white okay and then you can with the computer color them so that's why we call these these false colored scanning sems s stands for scanning electron microscopy and this is where you get a 3d image so this is scanning across the surface so transmission the electrons are going through they're transmitted through scanning the electrons go across the surface so you get these really cool um looking pictures so like this is these are red blood cells and some macrophage and some fibrin in a blood clot this is a chloroplast um so we're still seeing um internal structures but you can see how it's like 3d like you can you can kind of feel the feel you can kind of envision the thickness and the depth okay so a scanning is going to give you a 3d surface image transmission is going to give you this 2d flat but it's all about details but this is a much greater magnification so let's make sure you understand the difference between magnification and resolution so magnification as it says here is how much bigger a sample appears than what it truly is so we've magnified onto this dog's nose resolution is really about the detail so can you distinguish between two spots okay two images so you can see that you have much better resolution on the left hand side it's all blurry over here so this would have lower resolution they're both images at the same magnification it's just um which camera actually has better optics to to resolve or to clarify these different um what am i trying to say i think you know what i'm trying to say um cameras or microscopes can have higher resolution higher ability to look at objects and be able to tell that they're distinct okay um good so one more part i want to talk about um in this video is what makes a cell a cell and y cells are small and then we will pause and then we will go on to organelles of the cell okay so all cells have four essential components and those four essential components are a cell membrane okay so you might also see this called a plasma membrane same thing it's basically the border of the cell so prokaryotic cells have cell membranes eukaryotic cells both animals plants fungi protists all have cell membranes all cells have something called cytoplasm and we're going to define this in the next video but cytoplasm is the fluid inside all the cells all cells have dna as the genetic material we talked about this in the last video how some viruses don't have dna as their genetic material viruses don't have a cytoplasm some viruses do have a membrane we call it an envelope wrapped around it but they steal it from the cell they've infected the last thing that all cells have this is our fourth is ribosomes and again we're going to talk about those in a minute but they are for protein synthesis so four components for all kinds of cells cytoplasm dna ribosomes cell membrane this allows the cells to have their own genetic information and to be able to produce the proteins that they need okay last topic for this video is why are cells small so if you compared um a little chihuahua to a big elephant they have the same size cells elephants just have more cells because they're a bigger organism cells have to be small because of something called diffusion and i got this image from this website here and if you scroll down to the bottom there's a good little video about diffusion diffusion is just the passive movement of molecules from high to low concentration and we'll actually talk a lot about diffusion um i think in the next chapter so molecules have to be able to get from the surface of a cell through the plasma membrane to wherever they need to go in the cell and waste molecules need to get from the cell out and these don't have little motors to move them around it's all movement by diffusion so if you have a small cell the molecules can diffuse and they don't have a long wave to go as you increase the size of a cell you can see that the molecules got about the same distance but they never made it all the way to the inside and that would mean that if this was a real cell that cell would be kind of starving in there or it might have a lot of waste to build up so cells have to be small because of diffusion because of this passive movement of molecules the concept that we want to talk about is this surface to volume ratio and what you want is you want a large surface area so think your plasma membrane to small volume ratio so you want a large surface area you want a small volume and so if cells are really big like this they're um i didn't put the ratio on here well um they have less surface so the molecules can only come in here and here and here and the volume is so big that the cell wouldn't survive so what's it better is to have a whole bunch of small cells which have a larger surface area to volume ratio now you might be thinking um let's see if i can go back okay look at the big size difference between prokaryotic cells and eukaryotic cells how can a eukaryotic cell work if it's so big compared to a prokaryote and that's because eukaryotic cells have organelles so all of these organelles here in this paramecium and there's a whole bunch that you can't see they take up space and so molecules can get to them and then sometimes the organelles can take them where they need to be so you can have a larger cell if you have organelles those help with the task those make the cell more efficient so that's why a eukaryotic cell that looks so much bigger than a prokaryotic cell still functions but the concept of why our cells smell is because of diffusion and therefore you want a large surface area small volume okay so next we're on to parts of a cell you will have a um sheet like this i encourage you to fill it out maybe in a day or so and test yourself with this this is a great way to study so we're going to stop here and the next lecture video will be about eukaryotic organelles