Welcome to our review on cell structures so the first thing we actually need to understand is that when we're talking about cells they come in two types so we've either got procaryotic cells which are bacterial cells or we've got eukariotic cells which are plant and animal cells now one of the kinds of questions they could ask you about on the exam here is to compare the differences between the procaryotic and eukariotic cells so the first difference that we find is that in a procaryotic Cell there is no nucleus the DNA is just free floating whereas in a eukaryotic cell we have the nucleus that contains the genetic material if we then compare the actual complexity of those cells what we find is procaryotic cells are relatively simple whereas eukaryotic cells are more complex and then the last comparison we'd make is to do with their sizes so a procaryotic cell is between 1 micrometer to 10 micromet whereas the eukariotic cells are bigger being 10 microm to 100 microm and just remember that when we're talking about a micrometer then if we think about how this actually compares to a number we're more familiar with in terms of a millimeter then 1 mm is the same as 1,000 micrometers so even when we're talking about eukariotic cells being quite big in the grand scheme of things they're very tiny still so we now need to understand the the different structures that we find within the different types of cell so the first one we need to look at are animal cells now this should be rather familiar to you from keystage 3 your animal cell is typically like the fried egg shape so you've got the actual nucleus in the middle there that greenish color bit in this diagram you've got the pink blobs there which are the mitochondria the cytoplasm obviously is the jelly-like substance and then surrounding that we have the cell membrane now do remember to be really careful not to write down cell wall anytime we're talking about an animal cell it's always the cell membrane second type of cell we need to know about are plant cells and again this is something you should have done back in keystage three so slightly more complex than our animal cells in terms of what we need to know for our exam we still have some of those same features as we saw in our animal cell so we have the nucleus still you've got the cytoplasm we've also got the mitochondria there and the cell membrane which is the Inner Line around the outside however we also have additional cell structures there so we've got the vacuo which is a thing that fills up a lot of the inside there we also have those green structures which are chloroplasts and then finally the outermost line around our diagram there is representing the cell wall which is made of cellulose in our plant cells the final type of cell we need to know about are the procaryotic cell so the bacterial cells now this is a very different diagram to the other ones we've seen because obviously we've gone from eukariotic cells with the animal and plants to the procaryotic cells here with our bacteria now what we will find is if we look at the actual structures that we find there are four that you can see are underlined there in red now those are the ones that are present in all procaryotic cells so they will all have genetic material which is usually found as this big loop of DNA they all have the cytoplasm the cell membrane and the cell wall but in other bacterial cells they have some additional features but these aren't present in all bacterial cells so we've got the fella off the right hand side there which act like a tail you've got the plasmids which are small Loops again of genetic material you've got the py which are actually little tiny hairlike projections there on the outermost surface and the Slime capsule which goes around the outside of our cell wall so you need to make make sure that you can identify and label all three of those types of cells with those key features so if we take a little bit longer to think about these procaryotic cells then first and foremost we need to remember that bacteria are unicellular so that means that they're only made of a single cell so these are actually the smallest living things that we've got on planet Earth because they're single celled you can't get smaller than that and they are classed as living things because they carry out those seven life processes that hopefully you remember from keystage three there another part of this is we do need to know some examples of procaryotic cells so there's three on the right hand side there that are quite common types of bacteria so you got streptomyces streptococus and eera coli or eoli the one that causes all that lovely food poisoning so those three are common examples of bacterial cells and you can see from the diagrams that I've given you there of the actual bacteria themselves they all have very different structures so they different shapes they've obviously got different structures around the outside so the next thing we really need to know about uh where these subcellular structures are found and also what they actually do or what their function is so on the next couple of slides what we've got are some tables that take you through the key bits so we're going to start off with the nucleus which hopefully we remember from keystage 3 is all to do with controlling the cell and that's the big that contains the genetic material so that's what we're going to find in both of our eukaryotic cells so plant cells and animal cells but will not be found in a procaryotic cells because they have no nucleus the cytoplasm which is the site of our chemical reactions is found in all three types of cells there cell membrane which will control what enters and leaves the cell because it's what's called a partially permeable or selectively permeable membrane then that's present in all three of our cells there and another thing that it also has are these things called receptor molecules which are all to do with communication between cells and they're actually embedded on the surface of our cell membrane our fourth subcellular structure or organel are the mitochondria now these ones contain enzymes for respiration and they're also therefore the site that respiration occurs and you'll find those in both plant and animal cells the cell wool which is made of cellulose in our plants or peptid ofly can in our procaryotes so do go careful not to mix up the material that the cell wall is made from and do make sure you know how to spell peptidoglycan because they were picky on that on previous questions I've seen now what we'll find is that the cell Wall's whole function is to do with supporting the cell So that obviously plants can grow without a skeleton but it's not found in animal cells the chloroplast is next and that contains this green pigment called chlorophyll which is got the whole purpose of trapping that light energy from the Sun in order to carry out photosynthesis so that's only found in plant cells last one on this one the vacuo this contains a substance called cell sap and again this is all to do with helping support the plant because as it takes in water it pushes out against the cell wall and gives it that rigid structure so only found in plant cells for that one our next subcellular structure then is the free genetic material so this is typically a circular strand of DNA that's found in the cytoplasm which then contains the genes required for all of those basic proteins to be made so this is only found in our procaryotic cells because both plant and animal cells have a nucleus that contains the genetic material the fella comes next and that's all to do with allowing the cell to move so basically it spin and allow that cell to move through a fluid environment and that again is only found in our prot carotic cells third one is our py so these are those little tiny hairlike projections on the outermost surface and their whole function is to do with allowing that cell to attach to surfaces and also to other cells and when they've connected onto other cells they actually use the py to transfer genetic material between the two bacterial cells there again only found in our procaryotic cells slime capsule comes next and this is all to do with protection so by having a slime capsule around the outside it's actually going to protect the cell and stop it from drying out but it also helps it to stick on to smooth surfaces as well and again only found in our procaryotic cells there the last one the plasmid this is a circular piece of DNA and it contains additional genes so these aren't the genes it needs just to survive these are additional ones and usually you'll find things like antibiotic resistance for example are found on these little plasmids now the good thing about those plasmids as far as bacteria concerned is they can be transferred from one to another so that's how that bacterial resistance is able to spread so what we find again only found in procaryotic cells not in any of the eukaryotic cells