hello and welcome to the lccc biology 1010 lecture on the cell during this lecture you'll get a brief overview of the cell theory as well as cell structure this includes the components the pieces and organelles that make up the outer structure the inner cytostructure as well as the specific organelles of various different types of cells in living organisms so as a reminder the cell is the most basic unit of living hierarchy that we would consider alive so what does this mean what is different between a cell and a rock or between a cell and water hopefully you will see that and it will become more clear throughout the lecture to begin with the very first cells were discovered in 1665 by looking at oak bark these plants are extremely easy to see the cells due to the rigid cell walls because of these robert hook named the cells that he saw cellully or little cells this leads us to the first component of what we call the cell theory which was first proposed 200 years after the discovery of the cell that's 200 years of thought of scientific exploration and technological advancement and one thing to keep in mind is that this cell theory did not start as a theory rather it started as an explanation of the phenomena and observations of schleiden and schwann as well as those scientists who came before them now cell theory has three primary components the first is that all organisms are composed of cells or these tiny box-like structures the second component is that cells are the smallest living things additionally cells may only arise from pre-existing cells what this tells us is that all cells today every cell in your body represents a continuous line of descent from the first living cells when talking about the cell it's important to keep in mind a sense of scale or the size that we're talking about okay so when we're looking at these things if we were to compare cells which we find in prokaryotes and eukaryotes to that of viruses we've noticed that a virus is much much smaller than even the smallest living cell on the order of a hundred nanometers okay now we can compare that to the smallest prokaryote or bacterial cells and those would be one micro micrometer large and to give you a sense of a micrometer if you were to look at a ruler and look at the metric side and look at the millimeter and you could fit a thousand micrometers in between every millimeter mark what that means is that every mark on that ruler could contain ten to a hundred different cells depending on whether they were prokaryote which tend to be smaller or eukaryote which tend to be larger in order to observe these tiny structures we have to go towards microscopy or the use of microscopes now one branch of microscopy is focused on using light as the energy source these are the types of microscopes that you will become familiar with in lab and we use these to observe general structures such as large cells like these cheek cells and we can attach different stains in order to look at specific organelles we can also attach fluorescent molecules to get an even better idea of what is going on inside that cell however if we want an even better idea we'll use equipment known as electron microscopes and we have a couple of varieties of electron microscopes it's important to recognize that these microscopes allow us to see images magnified up to 200 000 times and so we have scanning electron microscopes which allow us to see surface structures and see these these tiny microscopic structures or animals in three dimensions and so here we can see uh a magnified image of a tardigrade or or a water bear and here we can see a magnified image of a blood cell but what about what's going on on the inside of these structures for that we would use something called transmission electron microscopy which allows us to see the internal structures so here we're looking at the inside of one of those blood cells speaking of these cells there are two basic types of cells based on their organization earlier you heard me use the term prokaryote and eukaryote prokaryotes are organisms which are extremely small and don't have compartments you simply have the outer membrane and some dna whereas the eukaryotes also have that outer member outer membrane but in this case we have some compartments inside the cell that we would term organelles okay so in this case we would find dna but this dna is wrapped in a membrane bound organ now known as the nucleus okay so prokaryotes bacteria still have dna as all cells do that dna is just not contained in a nucleus they do have that outer cell membrane but nothing else going on on the inside these cells are extremely simple in structure eukaryotic cells on the other hand are extremely complex not only do they have the dna wrapped in this membrane-bound nucleus but they have hundreds of other organelles such as mitochondrial mitochondria golgi apparati and endoplasmic reticulum so let's take a moment to watch a video to get an overview of the parts of the cell even if you're just studying a lot of work is going on in your cells let's zoom down and check it out we've arrived in the space between two cells a sticky coat called the extracellular matrix holds the cells together each cell is surrounded by a flexible plasma membrane with an incredible number of projections docking stations and channels let's dive into one of these channels to enter a cell whoa look at this place these girders and cables make up the cytoskeleton the structural framework of the cell they also serve as tracts for transporting cargo from one place to another all this activity in the cell requires energy in the form of atp molecules which are made here in the mitochondrion notice the outer membrane and the inner membrane with its numerous infoldings many of the molecules involved in making atp are built into the inner membrane all those folds increase the inner surface area enabling more atp to be made moving towards the nucleus we pass by layers of internal membranes the nucleus is enclosed by a double membrane called the nuclear envelope let's enter the nucleus through a pore the nucleus houses the genetic material of the cell dna which carries the blueprints for making the cells proteins almost two meters of dna is crammed inside the nucleus how does it all fit the dna is wrapped around proteins like thread wrapped around spools look this section of the dna has unwound and a different protein has attached to the dna dna is being used as a template to make mrna mrna molecules travel from the nucleus to the cytoplasm carrying the instructions for making specific proteins in the cytoplasm a ribosome clamps onto a strand of mrna the ribosome ratchets along the mrna building a new protein some proteins stay in the cytoplasm others like this one are processed in special compartments within the cell protein processing and certain other metabolic activities occur in the endomembrane system the cell's network of internal membranes the endoplasmic reticulum or er is part of the endomembrane system there are two types of er rough and smooth rough er is covered with ribosomes smooth er lacks ribosomes lipids are made in the smooth er let's go inside the rough er note that you can still see the ribosome on the outside surface the ribosome is manufacturing a new protein which continues to grow inside the er completed proteins move to the edge of the rough er and depart in a vesicle that buds off from the er membrane some vesicles fuse with the golgi apparatus another component of the endomembrane system in the golgi proteins undergo further processing finished proteins are then packaged in vesicles that pinch off from the golgi and are transported along cytoskeleton tracks some vesicles bind with the plasma membrane secreting their contents outside the cell other vesicles called lysosomes contain digestive enzymes here a lysosome fuses with a worn out mitochondrion and breaks it down each of the trillions of cells in your body is a dynamo of activity requiring millions of atps every minute but most people are unaware of all this activity in their cells so hopefully that gave you a good overview of the different components of the cell and we'll now go through each of those components in a little bit more detail but before that let's kind of look at the general comparisons of cells that we have so looking at this cell we know this is a eukaryotic cell it has the membrane-bound nucleus it has a mitochondrion which has several mitochondria which are also bound by membranes it has the cell membrane which is a component of all cells and this particular cell would come from the animal kingdom okay now compared to a plant cell which has a cell wall which we do not see in the animal kingdom we have the chloroplasts which are a unique plant organelle we also have this extremely large central vacuole which the plant cell uses to store water and we also have fungal cells which are extremely similar in appearance to an animal cell and notice the the mitochondria the lack of chloroplasts however in addition to these things we also see a cell wall around the fungal cell very similar to the plant cell and then we have an extremely variable group of organisms known as protista which for all intents and purposes is essentially just anything that isn't a plant an animal or a fungus typically the protists are single-celled organisms but they are extremely diverse so if we take our tour of the cell and we start at the outside of the cell and work our way in the first thing that we will find is the extracellular matrix okay this is a matrix of various proteins which allows for support and anchorage and can especially be used for signaling between different cells next in certain kingdoms we will find the cell wall these are found in plants fungi algae and other types of protists as well as some bacteria now each of these kingdoms has a different chemistry in terms of how the cell wall is made but they all function very similarly and that they add support protection and can even provide storage of whales if we look specifically at the plant cell wall we'll notice that it's made of this biomolecule cellulose this is provides the main support for the plant in combination with that central vacuole essentially what's happening is water accumulates in the central vacuole which takes up space inside the cell and pushes against the cell wall adding rigidity okay the cell wall additionally adds a layer of protection where molecules can travel through the cell wall without passing through the cell membrane into the inner workings of the cell as mentioned previously we can also store toxins and other wastes which just increases the protective ability of the cell wall especially against herbivory or other animals and organisms trying to eat the cells and if we look at the fungal cell wall this is instead made of a very complex assemblage of chitin carbohydrates and other proteins okay moving internally now to the cell membrane that component that all cells whether prokaryotic eukaryotic animal fungal plant have in common and this cell membrane will have an entire lecture on so we'll get to know the membrane more later but for right now it's important to know that it's made of phospholipid proteins which have a hydrophilic or water loving area and a hydrophobic or an area that is not attracted to water they do have this double layer here of these phospholipids and everything that goes into or out of the cell has to cross this membrane so this membrane contains various structures embedded throughout the membrane to aid in transport support and communication and here we can see a more close-up view of that cell membrane all right and notice that this goes all the way around the cell and to protect every part of the cell and separate it from the outside environment okay next now that we are in the cell we should talk about the cytoplasm cytoplasm is essentially [Music] everything between the cell membrane and what we'll learn about the nuclear membrane okay you can think about this as a nice soup okay the cytoplasm is the soup okay now that includes the liquid as well as every organelle and other structure in there if we wanted to discuss just the juice or the broth then we would discuss the cytosol notice the common term cyto okay in biology the cyto prefix tells us that we're talking about the cell okay moving more internally we get to the the network of support and movement within the cell this is the cyto there's that prefix again cyto meaning cell cytoskeleton we have three main types of filaments or rods within that make up the cytoskeleton first off we have the micro filaments these microfilaments which we can see here in red along the edge or the membrane of the cell typically stay around the surface of the membrane and they change the shape and are responsible for movement of the cell we also have microtubules which are more like the large bones of our skeleton providing large support and then we have the intermediate filaments which basically attach everything to everything okay so these micro filaments these uh these thin rods also known as actin filaments which are typically found around the edge of the cell are mostly used for movement i think muscle contraction okay or think about an amoeba moving around it's that movement is caused by the contraction of these actin or microfilaments and the microtubules or these thick strong almost analogous to to the large bones in our skeleton do most of the support work and and provide the framework for the cell we'll see later these these microtubules also provide sort of a highway or a track for different organelle and vesicle movement okay the intermediate filaments many of you are very familiar with because these are often found in structures such as hair scales and fingernails these are permanent rods that help the cell maintain its shape so these these filaments are attached like i said basically to everything and they keep all the organelles and other components of the cell in their proper place i've been using this term organelle quite a bit so now we will get to the organelles prior to this we were talking not about organelles which would be the membrane bound structures in the cell but more just the support structures so the first group of organelles that we will talk about are those comprising the endo membrane system this is the space where protein synthesis happens and so remember dna is housed in the nucleus where it's copied to make rna which is used to make proteins the proteins have to go somewhere okay now occasionally those proteins will stay will be made to stay in the cell but often the proteins are made to leave the cell and communicate or assist in other organismal functions when that is the case these proteins are built in the endoplasmic reticulum where they're then modified in the golgi apparatus and sent through the vesicles to the environment outside of the cell so if we look at this endomembrane system a little bit more closely first we find the brain of the of the operation this is the nucleus where all genetic information is stored what's interesting is that the nucleus is not surrounded by a single membrane but actually a double membrane communication with the nucleus happens via these small pores which help which help keep our genetic information safe and secure and prevent things like degradation so we can look at this this nuclear pore so here we have our our plant cell zooming in on our nucleus we can see here is that phospholipid layer you notice that we have two phospholipid layers which comprise a single membrane and with the nucleus we also have a second membrane okay and then within that we have these tiny pores which is where the mrna is allowed to leave the nucleus where it can be translated into proteins and that leads us to the endoplasmic reticulum whose primary job is production of those proteins okay so they smooth section of the endoplasmic reticulum is smooth because it lacks the ribosomes okay the ribosomes attach to certain portions of the endoplasmic reticulum which we would call the rough endoplasmic reticulum okay the the reason for this is remember ribosomes are important in protein production and the rough side of the endoplasmic reticulum is where proteins are being released the smooth side of the endoplasmic reticulum is being used to make lipids okay so remember that the ribosome is a complex protein structure it is not an organelle itself it is a protein complex involved in the synthesis of other proteins okay these come in large subunits and small subunits these are the dots of the rough endoplasmic reticulum the nice thing about these ribosomes producing the protein directly into the endoplasmic reticulum is that it makes it very easy to make and modify a whole bunch of proteins without having to cross these extra membranes once the the proteins are made in the endoplasmic reticulum we'll start to see some these membranes budding off and what we call vesicles very similar in nature to a lava lamp for those that are still familiar with lava lamps and so here you can see this process of budding makes it so that the the proteins or the contents of the vesicle can be transported into or out of the cell without ever having to cross this membrane okay once we're finished in the endoplasmic reticulum the next place the protein will go is the golgi apparatus you can think about this as the packing and shipping organelle the the purpose of this organelle is to modify any incoming molecules such as proteins maybe putting together subunits adding sugars or lipids and packing them off to then leave the cell hey um the vesicles which are kind of like baby membrane sacs really um are membrane bound structures uh that carry various enzymes or or other molecules around the cell remember they're using that cytoskeleton cytoskeletal network to move around other organelles outside of that endo membrane system would include the mitochondria the mitochondria are the powerhouse the power plant of the cell breaking down food usually in the form of sugar and turning that into chemical energy which can be used for various work functions throughout the organism it's important to remember that all eukaryotic cells have mitochondria and need to turn food into chemical energy this would include animals plants and fungi similar to the nucleus the mitochondria is also wrapped in a double membrane okay so we also need a way to make the sugar that the mitochondria are breaking down and that is the job of the chloroplast and we will find chloroplasts anywhere where we find photosynthesis okay similar to the nucleus and the mitochondria they are wrapped in a double membrane however different from the mitochondria the chloroplasts are responsible for taking light energy and converting that into food energy such as sugar additionally we'll find the central vacuole which is which is an organelle only found in plants and this is typically where 90 percent of the cell's water is found which makes this a gigantic organelle it's responsible for the turgidity or the stiffness of a plant and you all have experience with this if you've ever seen a wilting plant okay so notice when you don't water the plant will wilt this is because the central vacuole is shrinking and is not providing pressure against that cell wall once you water the plant and it becomes happy again the central vacuole fills back up pushes against the cell wall and increases the stiffness of the entire organism okay so let us review just a minute pause the video what type of cell is this how do you know that what organelles do you see you see a nucleus mitochondria notice we don't see any chloroplasts when there's no cell wall okay what type of cell is this well we still see our nucleus and our mitochondria but additionally this time we have chloroplasts a cell wall and a large central vacuole what about this cell we have mitochondria and a nucleus similar to the animal and the plant but we also have a cell wall surrounding it which we do not see in our animals okay notice we also have no chloroplasts and no central vacuole okay so let's take a minute to watch this pretty awesome video produced by some some workers at harvard which they do all of the great stuff and i would encourage you to actually watch this a couple of times the first time just to get a feel for what's happening and after that see how many organelles you can name while watching this okay to give you some background this is a white blood cell interacting with blood vessel cells okay i hope you'll take the opportunity to go back through and watch that youtube video a couple of times go through review the organelles what are their functions review the other structures the cytoskeletal components and what they're doing and i hope you enjoyed learning more about the cell