hi guys in this video we'll be looking at cell organelles the nucleus inside the nucleus the ribosomes and then we'll finish with a summary so the cell is obviously the basic unit of life and all organisms have forms of cells whether they exist just on their own or whether they're a multicellular organism such as ourselves or plants and many other species cells can have multiple different types and eukaryotic cells include the cells that we find in plants animals and fungal tissues or fungal organisms so that includes all types of plants all types of fungi which include mushrooms and other types of organisms like yeast and animals as well which range all the way down from insects fish and birds all the way up to large creatures like elephants lions tigers bears etc and eukaryotic cells are different from another type of cell called a prokaryotic cell so without going into too much detail prokaryotic cells often are talking about bacterial cells for example the pathogens that can cause us many diseases and when you look at the structure of the bacterial cells they have a number of marked differences compared to our cells which are called eukaryotic eukaryotic cells tend to be a little bit different and normally larger with more features and one of the most obvious features is that they have some membrane-bound organelles so remember the cell as an entirety has to be its own units and therefore it's separated by the outside environment with a cell surface membrane so this cell surface membrane surrounds the entire cell and all of its contents and you can think of the membrane as a lipid bilayer which we talk about in other videos in more detail but the other feature about eukaryotic cells is that inside we have all of these other structures which are in themselves discrete sections where different processes are happening and in order to be discrete units they have to be surrounded by their own membranes as well so here are all different types of membrane-bound organelles and in a similar way that we as an animal have organs inside of us like our heart lungs and liver the cell itself has its own kind of organs doing various jobs because it's in a cell we call them organelles and as we've said the organelles are components of the cells which have specific functions so for example here we have one of the organelles which is known as a ribosome so the ribosome has a variety of functions but its main one is protein synthesis and collectively all of the organelles as there is a range of different organelles they carry out all of the functions that the cell needs to do so first of all let's talk about one of the largest and most obvious organelles in the cell well the word eukaryotic actually means containing nucleus or a eukaryote means to contain a nucleus so prokaryotes don't have this the largest organelle in the eukaryotic cell is the nucleus and when you look down most microscopes the nucleus is the most obvious feature inside the cell is normally a spherical kind of blob so this would be the nucleus so roughly speaking it's a spherical structure so it's in the shape of a ball and usually if you look inside the nucleus there's a dark patch or a dark little blob which also accompanies the material inside of it so if we look down a micrograph here we've got two types of micrograph here's one cell and then if you look inside the cell there's this spherical or circular structure obviously it looks circular because we've cut through in 3d and this would be the nucleus and inside of here we've got that dark blob which you can see sometimes you can't always see this because in this case there isn't one but most of the time it is there and then if we look on this we've got a light micrograph from a light microscope and every time you see one of these blobs this is a nucleus and therefore usually this each corresponds to one single cell the function of the nucleus is to contain the dna of the cell and the dna is what contains the information for producing proteins so obviously all of our cells need the instructions on how to build us and how to allow us to function and make everything that we need in order to survive a healthy life that information is stored in a molecule known as dna we've got more videos on how dna works and the structure of dna so don't worry too much about that now but dna basically holds all the genetic information and the dna is such a long molecule that it takes up a lot of space in the cell so all of it has to be taken up and stored into the nucleus where it's also protected and then what happens is the dna codes for instructions for making proteins all of the proteins which build us up which build up our skeleton our organs all of the enzymes going around the body the hemoglobin carrying the oxygen everything is coded for back from the dna so this is the purpose of the dna although actually the dna doesn't exist just on its own it doesn't just sort of bundle up into a ball it is packed with its own proteins known as histone proteins and the histone proteins basically help to package the dna so it's nice and compact and it takes up less space as an interesting fact one single cell of the human body has two meters of dna inside of it so obviously it has to be packed up in such an efficient way and this is achieved by these proteins known as histones and there's various different types so the dna kind of wraps itself around these histones like this and when we have the dna combined with these histones we call it generally chromatin so when you were to look into a cell look into the nucleus you would see dna all in various different forms and shapes combined with these histone proteins and together inside the nucleus we call this the chromatin and the nucleus itself is separated from the rest of the cell by a double membrane and we call this the nuclear envelope because an envelope kind of has two boundaries to it and therefore it makes sense to call it this so here's the structure of the nucleus and this structure surrounding all of this chromatin inside is a double membrane and we call this the nuclear envelope and then inside here you would see all of this is chromatin and there you can see that dark blob we were talking about just now in the micrographs so because the nuclear envelope is a double membrane it's made up of an inner membrane and an altar membrane separating the nucleus from the rest of the cell the reason why this is important is because the dna and the proteins in here are very fragile and the cytoplasm of the cell contains many many enzymes and molecules which are kind of carrying out various functions and the worst thing to do would be allow this dna to come into contact with all of these harsh environments so here we can see that we've got two different parts of the membrane we've got the outer which is itself a lipid bilayer and then we've got the inner which again is the same thing so each of them are a lipid bilayer and we form two membranes on top of each other all around the nucleus and finally the nuclear membrane has these nuclear pores which are very very small holes in the nuclear envelope if we zoomed into the nucleus and looked at its edge here we can see we've got these outer and inner membranes and these structures are known as the nuclear pores and they just act like pores on the skin which allow things to exit and enter and specifically two things can travel through these pores mrna or messenger rna and ribosomes and they travel from the nucleus to the cytoplasm or backwards through nuclear pores so we've got mrna and don't worry about what mrna does too much now it's basically a code containing the information from the dna and it needs to go out in order to allow protein synthesis and this protects the dna from leaving itself because as we said this environment can be very harsh for it and it will only fit through these pores and as well as that ribosomes can fit through too and we'll talk about ribosomes a bit later on so let's look at what a bit more of the detail inside the nucleus we've already mentioned that it contains chromatin but there's another feature called the nucleolus and the nucleolus is the dark blob that we were talking about before it contains very densely packed up dna and protein so remember those proteins are called histone proteins so here we've got a diagram of the nucleus you can see the envelope with multiple pores and you can see that inside we've got all of this chromatin i.e genetic material and proteins and then here we've got this nucleolus which is the darker denser-packed dna and protein densely means that it's packed very tightly together so what is the function of this nucleolus well the nucleus is involved in making ribosomes so the ribosome is a type of organelle and we've already come across it before but essentially it helps making proteins so it's involved in protein synthesis and it's made inside the nucleolus and then sent out to the cytoplasm and the rest of the nucleus essentially contains dna less densely packed with protein so we've talked about the dna interacting with histones but it's less densely packed and therefore less dark in the micrographs so this area is a lot less dense and this area would be slightly denser and therefore make up part of the nucleolus and finally the nucleus has its own version of its cytoplasm so remember the point of the cell and the membranes is to separate compartments in the cell we've got the cytoplasm which you think of when we say the cell and the nucleus usually this area between them is the cytoplasm and that's generally the kind of the fluid environment and the solutions and molecules the cell has to carry out its function but all of these other membrane bound organelles aren't just full of nothing they have their own fluids and solutions too so they have their own kind of versions of the cytoplasm and often the environment is slightly different if they are all exactly the same there'd be no point in having these compartments but often there are some organelles with different environments like they're more acidic or more dangerous and they need to be separated from the other areas so the cytoplasm inside the nucleus which is where the dna and chromatin and everything lives is called the nucleoplasm so the nucleoplasm just kind of surrounds the nucleolus the chromatin and everything inside the envelope so this would be the nucleoplasm so another important organelle that's found is called the ribosome and the ribosomes are involved in translating the genetic material into the protein so remember the function of dna is the genetic information and instructions to form proteins and it does this via another intermediate known as mrna and we've got videos again on the detailed structure and process of this but mrna is essentially the messenger that can be taken out of the nucleus so the dna can stay in the nucleus and be protected from the harsh environment outside but this process is carried out by the organelles known as ribosomes so ribosomes can be found in two different places some of them are found on another organelle known as the endoplasmic reticulum so the endoplasmic reticulum are these kind of long elongated sac like structures and they kind of look like pita bread surrounding the nucleus with various branches and connections and essentially they can bind to this reticulum in various places and just sit in the membrane of the organelle and therefore they can sit in this organelle quite closely the other ribosomes can be found free floating in the cytoplasm so the cytoplasm remember is all the solutions making up the rest of the cell some of them can be found just floating around and here we've got a micrograph of parts of the endoplasmic reticulum so you can see these membrane kind of pita bread like structures it almost looks like a load of long wiggly fingers kind of interacting with each other and then the black blobs that you can see attaching to the membrane are the ribosomes so these are the ribosomes and of course the ones that aren't attached to any membrane are the free ribosomes so the ribosome itself contains two separate parts or sub units we call them there's a smaller subunit called 40s and there's a larger one called 60s and they come together when they are involved in protein synthesis so this large gray one is the 6ds ribosome subunit and the blue one is the smaller 40s ribosome subunit and essentially they come together for protein synthesis so you also have to be aware of what these ribosomes are made of as well because they're made of quite specific molecules they're made from a type of rna known as ribosomal rna and they also contain protein as well so we've already mentioned that rna can be of various types and one of them was mrna mrna was a messenger to get instructions out of the cell nucleus you can also have ribosomal or rrna and it's essentially just involved in building up these ribosomes so it's in both subunits and it gives it general structure and what we also find is some protein strands interwoven into that rrna and together these make up the general structure of the ribosome and then the ribosomes ready to help read mrna and create a protein again a lot more of detail in this is found in other videos hey guys i hope you enjoyed the video if you're looking for an amazing a level biology resource join me today in my series of engaging bite size video tutorials just click the snap revise smiley face and together let's make a level biology a walk in the park