hi everyone and welcome to a level biology with miss estrich in this video i'm going to go through prokaryotic cells for a level biology so let's start off by having a look at what you actually need to know for prokaryotic cells so you need to know the key differences between the structures in a prokaryotic cell and a eukaryotic cell so i'm going to summarize them here but then go through each one in more detail or at least the ones that need more explaining so the cells that are prokaryotic are much smaller they have no membrane-bound organelles they do have ribosomes but they're much smaller in size they don't have a nucleus they have a cell wall but it's made of a different chemical called murine and sometimes they could contain plasmids a capsule around the cell and flagella and we've got an example of a prokaryotic cell here this is a particular type of bacteria but not all bacteria look like this but bacteria are our key example of prokaryotic cells so going to start with the no membrane-bound organelles and to keep this as a comparison i've listed here some of the organelles that you have in a eukaryotic cell just to compare it to the prokaryotic cell so they will have ribosomes as do eukaryotic cells but they won't have any membrane-bound organelles and that's what we also have here in this list some examples that you would find in eukaryotic cells so mitochondria chloroplasts endoplasmic reticulum golgi apparatus or body and the nucleus those are all membrane bound so you do not find them in prokaryotic cells then if we have a look at the ribosomes because both prokaryotic and eukaryotic cells will have ribosomes in them and ribosomes are very small they're made up of two subunits which we can see here represented by the two different colours and all they're made up of is proteins and rrna and the differences between the two are the size so the prokaryotic cells have what we call 70s ribosomes and they're much much smaller eukaryotic cells will have ats ribosomes and these are found in eukaryotic cells note here as well it does actually tell you that in eukaryotic cells in the mitochondria and the chloroplast you do actually find some 70s ribosomes as well and that is so that those organelles can continually create their own proteins and those proteins are generally enzymes for respiration and photosynthesis next if we compare the nucleus eukaryotic cells have a nucleus so that means they'll have a nuclear envelope with pores in there'll be the granular jelly-like material in the middle called the nucleoplasm the chromosomes are linear and they have histone proteins bound to them and there's also a nucleolus inside which is where rna is produced or our rna is produced in particular and ribosomes are made as well in contrast prokaryotic cells do not have a nucleus and instead we can see here they have circular dna which is just loose within the cytoplasm and there are no histone proteins bound to it so it's not membrane bound if we compare cell walls next not all eukaryotic cells have a cell wall it is only the plants and fungi and the chemical that is within the cell wall differs as well so plants have cellulose cell walls fungi have chitin which is a nitrogen containing polysaccharide and prokaryotic cells they contain a glycoprotein in their cell wall which is called murine then we go on to the three final structures which are only present in some prokaryotic cells so a plasmid is this small loop of additional dna it normally only carries a few genes and that is where you would find antibiotic resistance genes if a bacteria has one so not every single prokaryotic cell will have plasmids the capsule this is a thick slimy layer on the outside of the cell wall and it's made up of a protein the function of this is to stop the bacteria from drying out or in other words desiccating and also it helps to cover the antigens on the outside and therefore it helps to hide and protect the bacteria against the host's immune system but again capsules aren't found in all prokaryotic cells the final structure which again you don't find in all prokaryotic cells is the flagellum and some bacteria might have multiple so we'd say flagella flagellum is the singular and what the flagella do is they rotate at the base so it's like a tail spinning round and round and it's then like a motor and it helps to propel the bacteria so that it can essentially swim and that is it for what you need to know about prokaryotic cells for a-level biology i hope you found it helpful if you did please give this video a thumbs up you