so in this video we're going to look at functional anatomy of eukaryotic cells and so this will be chapter four and in the last lecture we looked at prokaryotic cells and so now we're going to switch gears and look at eukaryotic cells so let's start by discussing eukaryotic cells an overview first and then we'll go into specific structures that are found within eukaryotic cells everything that lives is made of cells even us although we can't see them trillions of cells within our body work together to give us the gift of life these tiny units of life fascinate biologists like boyce rensberger the entire human body is made out of cells for the things the cells have made such as bone skin is made of cells your heart is made of cells the muscles that operate the the body so that you can move these things are all made of cells including the brain itself which sends electrical signals around from one cell to the other so that we can think all these different kinds of cells work fundamentally the same way when you look inside the cell you see the same kinds of structures [Music] cells come in all sorts of sizes and shapes they're so small that we need a microscope to see them [Music] inside of every eukaryotic cell is a microscopic factory that runs off chemical reactions at the center the nucleus acts as the cell's brain and controls its activities it also holds the dna the instructions for life the cell's membrane protects each cell and takes in the raw materials it needs to stay alive water nutrients and waste move into and out of the cell all the time these materials may hitch a ride along the cell's transport network a network made up of microtubules and intracellular membranes the cells transport network picks up transports and delivers material throughout the cell the cell breaks down raw materials into the building blocks it needs to grow this ability to take in vital materials allows the cell to function and perform specific tasks the instructions that are in the cells starting in embryonic development tell each cell how to change to take on a new function also the cells monitor the activities going on if there's a wound the cells can sense that and they will send out the message to other cells to come and repair the damage so all this keeps the whole body on a kind of an even keel our cells work together in extraordinary ways the heart for example is made up of muscle cells with the tendency to twitch separately they twitch to their own rhythm but together they beat as one millions of them work together to give us a heartbeat these muscle cells survive as long as we do but throughout the body cells die and get replaced all the time our body produces new cells through mitosis the process where one cell divides into two since we're constantly losing and replacing cells most cells in our body are actually younger than we are cells are extremely diverse both in structure and in function and so what you're looking at on the left hand side is you're looking at red and white blood cells that line a human blood vessel and the red blood cells are the ones that have that kind of concave disc shape and the white blood cells are the ones that look a little bit more like they're spiky um but those are basically two types of human cells that are in the blood the picture on the middle is showing you cells of a brewers yeast which is used to make wine beer and bread and that is saccharomyces cerevisiae whose name translates to sugar fungus that makes beer on the right you're looking at cells of a spinach leaf and so you can see that the cells are very diverse in terms of their shape and their what we call their morphology so this is just an overview of kind of what we're going to learn throughout this chapter we're going to start with an introduction to cells we're going to compare different types of cells bacterial cells versus plant cells versus animal cells etc we're going to cover the nucleus and the ribosomes so talk about how proteins are synthesized for example we will then move on to the endomembrane system this membranous system that is used in the cell we will talk about energy converting organelles and then lastly we'll talk about the cytoskeleton elements and cell surface structure so we'll start with our animal cells animal cells are bound by a membrane because again all cells are bound by a membrane they do contain membrane-bound organelles so for example nucleus mitochondria etc animal cells do not have a cell wall they do not have a cell wall and as a result they are much more flexible they're able to change shape more readily than let's say a plant cell there are several structures in animal cells that are unique to animal cells but not found in plant cells one would be an organelle that's called the lysosome and the lysosome's job is that it serves as the recycling center of the cell meaning it allows the cell to break down worn out organelles it also allows the cells to digest macromolecules animals have them plants don't plants instead of using these small lysosomes plants do a lot of those similar activities in a large central vacuole but it's different than a lysosome animal cells have a structure that's called a centriole and you can see on your diagram here it's labeled as a centrosome it's this little yellow t-shaped structure right in the middle or the lower left of your picture in between the mitochondria and that little t-shaped structure collectively is called the centrosome and it's made up of centrioles animal cells have them plant cells don't they're used for cell division animal cells have flagella some of them plant cells typically do not except for in some plant sperm if we look at our plant cells plant cells again are bound by a membrane they do contain membrane-bound organelles because they are eukaryotic they do have a cell wall and their cell wall again is going to be cellulose which is a polysaccharide there are several structures that are found in plant cells but not in animal cells plant cells have chloroplasts the chloroplast is this green organelle here the chloroplast is used for photosynthesis it allows the plant to be an autotroph for a self-feeder it can take carbon dioxide water and sunlight and convert it into glucose it's able to make its own food plant cells also have a large central vacuole this big structure that is primarily water but it serves other purposes in the cell as well which we'll talk about in a little bit plant cells have a cell wall cell wall made of cellulose plant cells have a structure called the plasmodesmata these are basically the pores in the cell wall that link two plant cells together it allows the plant cell to communicate and to share materials between those cells animal cells don't have a cell wall therefore they don't have these plasmodesmata it works a little bit differently in the animal cell so what we're going to do is we're going to talk about eukaryotic organelles and what are organelles where well they are membrane enclosed structures that are used to compartmentalize a cell's activity and so these are again they're like tiny organs if you recall back to our hierarchy of life right organelles come before cells cells come together to make a tissue and so on and so forth so organelles are these tiny compartments within the cell the organelle and other structures of the eukaryotic cell can be arranged into four basic functional groups the first group is going to be the nucleus and the ribosomes that are used to carry out the genetic control of the cell we have organelles involved in the manufacture distribution and breakdown of molecules including the endoplasmic reticulum the golgi apparatus the lysosome vacuoles and peroxisomes we have mitochondria in all cells and chloroplasts in plant cells that are used in energy processing and then lastly we have a group of structures that are used for structural support movement and communication between cells those are the functions of the cytoskeleton the cell membrane and the cell wall and so we're going to walk through and we're going to talk about what all of these various structures do so we're going to start off with the nucleus and the ribosome both the nucleus and the ribosome play a role in protein synthesis the nucleus is what's going to hold the genetic instructions meaning this is going to contain the genes it's where the dna is kept and so if we look at the way that dna codes for protein dna remember is the blueprint so in the nucleus we have our dna and let's say that the dna sequence so dna let's say the dna sequence is going to be t t t t a c so that's my dna sequence now if this is my dna sequence it's going to undergo what is called transcription an enzyme called rna polymerase is going to come in it's going to read the dna and it's going to synthesize a complementary rna the rna is based on the dna so if this was t this is a a a a a would pair with not t rna doesn't have t it's going to use u instead and then c is going to pair with g so this would be my rna sequence aaag that process going from dna to rna is referred to as transcription we are transcribing a similar language they're both nucleic acids in eukaryotic cells that rna undergoes something called rna processing it has a cap and a tail added to it it has structures called introns spliced out of the dna basically it's making a mature mrna and then the mature mrna is going to exit out the nuclear pore and it's going to go to the cytoplasm in the cytoplasm is going to be the ribosome and the ribosome plays a role in protein synthesis and so what's going to happen in the ribosome is that it's going to read the rna and it's going to synthesize the appropriate polypeptide chain so when the ribosome is going to do what we call translation it's going to read the rna and produce a protein so when the protein gets made aaa is going to code for a particular amino acid and in this case it's going to code for lysine aug is going to code for methionine and so on and so forth and so the rna is going to be red and it's going to synthesize a protein now notice that the language and rna is different than the language for proteins they are different types of macromolecules one is nucleic acid one is protein that is why the process of going from rna to protein that is referred to as translation so transcription happens in the nucleus because that's where the dna is and so the dna is going to be copied into mrna mrna is going to exit out the nuclear pore it's going to come to the ribosomes and the ribosomes are going to undergo translation we're going to read the mrna and they're going to synthesize the appropriate protein based on the dna sequence this is why the dna acts as the blueprint it gives the instruction for what protein to synthesize so if we look at the nucleus the nucleus you can think of like the control center of the cell it is surrounded by a nuclear envelope which is a two lipid bilayer membrane so again the nucleus is a membrane-bound structure it has two phospholipid bilayers and so that is going to contain the chromatin chromatin is referring to chromosomes so the dna and the associated proteins meaning the histones so when the cell is not dividing the dna is loosely associated in the nucleus and that's when it's referred to as chromatin which is going to be referring to the dna and the proteins that are involved in it the nucleus also has these pores they're called nuclear pores and the nuclear pore is going to for example allow mrna out of the nucleus so they serve as kind of a gateway for things to regulate what goes in or out the other thing that's also found in the nucleus is within the nucleus there is a structure referred to as the nucleolus so you can see it as this darker purple dot here the nucleolus is the site of ribosomal rna synthesis it makes what we call rrna so the nucleolus is responsible for ribosomal rna you can guess that ribosomal rna plays a role in the ribosome it's what's used to help make a chemical bond between amino acids it forms the peptide bond between the amino acids and the ribosome so the ribosomal rna gets synthesized in the nucleolus the nucleolus also plays a role in ribosome assembly because what you're going to see is that the ribosome is made of both protein and ribosomal rna and so that ribosomal rna that's made in the nucleolus gets put with the protein and it assembles those ribosomal subunits and so that's the other job of the nucleolus to assemble the ribosome in terms of the ribosomes the ribosomes are not membrane-bound organelles there is some debate about whether to call them an organelle because they're not membrane-bound but i would say it serves it's a structure that serves a particular purpose in the cell i call them an organelle but again you'll see a debate in textbooks about whether or not the ribosome is a true organelle in eukaryotic cells eukaryotic cells have what are called ads ribosomes ads is referring to it's based on the size of the ribosome so what that means is that a ribosome has two subunits it has a large subunit and a small subunit in eukaryotic ribosomes the large subunit is what we call a 60s and the small subunit is a 40s and total for eukaryotic is 80s this is 80s so large subunit is 60s small subunit is 40. yet when you put them together they're actually an 80s it's not a 100 even though 60 plus 40 is 100 it just has to do with the way that that's measured it uses a gradient method and collectively when two subunits are put together they don't measure at 100 they measure at 80. i won't ask you that on the exam but in case you were wondering in prokaryotic cells prokaryotic cells i'm going to color it a different color prokaryotic cells the large subunit is going to be a 50s small subunit is a 30s and total for prokaryotic is going to be a 70s so again 50 and 30 does not equal 80 it actually equals 70 in this case now why am i even bothering to tell you that eukaryotic cells use ads ribosomes and prokaryotic u70s that is important for several reasons first is that because eukaryotic ribosomes and prokaryotic ribosomes are different it allows us to have antibiotics that target bacterial ribosomes they target bacterial ribosomes because if those drugs inhibit protein synthesis in bacteria it's going to cause those bacteria to stop dividing the reason those drugs are useful is because they target the 70s ribosomes specifically and not the ads so they display something that we call selective toxicity meaning they target the bacterial cells without harming the host so that is one of the reasons it's important to know the difference between the ads and the 70s this is what allows us to use drugs that target bacterial ribosomes so erythromycin streptomycin the tetracycline those all are drugs that target prokaryotic ribosomes there are also two organelles that also contain 70s ribosomes so we have two organelles in eukaryotic cells that are what we call semi-autonomous which means that they can replicate independently of the cell they have some of their own dna they have their own ribosomes which means they can make some of their own proteins they're almost not exclusively but they're almost independent of the cell so in those two organelles they have 70s ribosomes and so interestingly if you think about it those two structures have 70s ribosomes while the rest of the cell uses ads ribosomes and we're going to come back to this later when we talk about those two organelles the reason that that's important is because it's believed that those two structures chloroplasts and mitochondria were believed to have once been free living prokaryotic cells so those structures actually evolved from bacteria in terms of the ribosomes they are the protein factories in the cytosol so again they're outside of the nucleus the proteins for the ribosomes are made outside of the nucleus for ribosomes cells that make more proteins have more ribosomes the cells are incredibly dynamic they are able to synthesize more of a particular organelle to meet demand so a cell for example like in the pancreas the pancreas is responsible for synthesizing many types of proteins involved in digestion for example those cells require to make a lot of protein and therefore those cells have a more abundance of ribosomes because cells that make more proteins have more ribosomes the ribosomes themselves again are composed of ribosomal rna that's made in the nucleus specifically in the nucleolus combined with the proteins that are made in the cytosol and they're assembled together those large subunits and the small subunits are assembled in the nucleolus as well so when we talk about ribosomes ribosomes can either be free or bound and what that means is that if we call a ribosome as being bound it means that it's attached to this membranous structure referred to as the endoplasmic reticulum and so the endoplasmic reticulum is this area in blue within the cell and so this is our endoplasmic reticulum we can also have ribosomes bound to the outside of the nuclear envelope but that's what we refer to when we talk about a bound ribosome they're actually bound to this membrane there are other ribosomes in the cell that are free and that just means that they're suspended in the cytosol and they're not bound to a membrane and so if we look at this electron micrograph here here are the free ribosomes that are not attached to the membrane here is the endoplasmic reticulum and you can see these little dots along it those are the bound ribosomes now why do we have two different types of ribosomes well they're used to produce different types of proteins if a protein is going to stay in the cytoplasm it's produced by these free ribosomes they don't need to go to this membranous structure so basically proteins that are made by free ribosomes are going to be proteins that are going to stay in the cytoplasm bound ribosomes are used to produce everything else it's used to produce membrane-bound proteins so proteins that will eventually end up in the membrane the reason for that is that when the cell synthesizes that protein it can actually synthesize it embedded in the membrane it makes it a lot easier to synthesize the protein into this membrane and then this membrane ends up going to the edge of the cell rather than trying to make an entire protein and then stick it into the membrane so proteins that are going to be membrane bound are going to be produced by the bound ribosomes secreted proteins meaning proteins that leave the cell for example as well as proteins that are located in other organelles so if a protein for example needs to go to the mitochondria to be used in cellular respiration it would be made by a bound ribosome etc so thinking about structures in the cell how do we kill foreign invaders i.e infectious bacteria without killing our own cells well many antibiotics bind to bacterial ribosomes which are sufficiently different from ours again bacterial ribosomes have ads ribosomes we have er sorry bacterial ribosomes our 70s versus our ribosomes or ads erythromycin streptomycin tetracycline chloramphenical all work by binding to bacterial ribosomes another way that we can target bacterial cells without targeting our own cells is that we have drugs that target bacterial cell walls remember that bacteria have cell walls humans don't so no harm done that again allows the drug to be selectively toxic it targets the microbe without targeting our own cells so that would be things like penicillin ampicillin amoxicillin etc would all be example drugs that target bacterial cell walls so back to our endoplasmic reticulum our endoplasmic reticulum again is continuous with the nuclear envelope and it's contained of these membranous tubules called cisternae if we talk about endoplasmic reticulum we have what are called smooth er and rough er smooth er is this picture in the blue they're smooth because they don't have ribosomes attached to them that gives them a smooth appearance rough er is referred to as rough because it's studded with those ribosomes those bound ribosomes and so it has all these ribosomes on it which give it a rough appearance smooth er and rough er do very different things while we're talking about the protein production pathway we are going to talk about the rough er and we will come back to the smooth er in just a minute so the rough er has these ribosomes on the outside and so what you need to kind of understand is that in fact all ribosomes start out as free ribosomes and so when the mrna comes out of the nuclear pore so when it comes out of the nuclear pore it's going to attach to a ribosome so the mrna binds to the ribosome and then we're going to start translation now as the ribosome is reading the mrna it's going to begin to synthesize the correct polypeptide now when it does this it's still free at this point how does the cell know that that ribosome needs to go to the endoplasmic reticulum well when that original protein is being produced there is what's called a signal peptide there is a sequence at the beginning of a protein that allows the prot or which allows the ribosome to dock on the endoplasmic reticulum basically it's a signal that tells the cell that that ribosome needs to go to the er so the bound ribosome is going to attach to the endoplasmic reticulum and so the rough er does a few different things one it's responsible for folding the protein proteins only function if they're in their correct conformation and so inside of the ribose or inside of the rough er is what we call chaperone proteins and the chaperone proteins are used to help fold the protein into their correct conformation so our polypeptide chain is going to be synthesized it's going to be folded and it's going to undergo processing so what does processing mean well that can vary depending on the type of protein for example this one that's shown here this is a glycoprotein which means that it has to have sugars added to it other proteins might need to be cut in very specific ways so like insulin for example when it's originally synthesized is not active it has to be cut to become activated insulin so in this case this protein is one that's going to be inside the endoplasmic reticulum now when it's inside the endoplasmic reticulum and it's been folded and it's going to be processed it's going to bud off in this transport vesicle so this membrane is going to bud off and it's going to leave as a transport vesicle now that transport vesicle will eventually go to the golgi apparatus so our step so far in our protein production pathway nucleus nucleus contains the dna it's the site of transcription mrna is going to exit out the nuclear pore mrna is going to come to the bound ribosome that ribosome is going to attach to the endoplasmic reticulum it's going to synthesize the polypeptide into the rough er protein is going to undergo folding and processing and then it's going to butt off in a transport vesicle to go to the next step the other thing that the rough er is responsible for is that it's responsible for the production of the membrane this is also a membrane factory for the cell it's able to synthesize phospholipids from precursors in the cytosol because this membrane that's here eventually is going to end up in the cell membrane and so the rough er is also a site of cell membrane production so our transport vesicle just left the rough er transport vesicle is going to come along and it's going to fuse with the golgi apparatus and the golgi apparatus has two sides it has what's called the cis side which is the receiving side meaning that's the side closest to the er and it has the trans side which is closest to the cell membrane and so if we look at the golgi apparatus you can think of the golgi apparatus as the ups center of the cell that's how i remember this one it's responsible for finishing sorting and shipping so packaging sorting and shipping think of what ups does right if you bring them a package they're going to package it up they're going to sort it meaning they're going to use the zip code to figure out where it goes and then they're going to ship it out and that's essentially what the golgi apparatus does for proteins it's made of these flattened membranous sacs the cisternae is going to be the internal space and so we have all these cisternae these internal spaces within the golgi and the cisternae contains specific enzymes it has enzymes to modify proteins and phospholipids it has membrane or secreted proteins inside those vesicles and then molecular tags such as phosphate groups may be added to identify the destination for the protein meaning essentially it's going to mark that protein for where that protein needs to go next that's the sorting it's going to mark it it's going to tag it and it's going to identify where the cell is going to ship that protein to next so here's a summary for the protein production pathway so again we start with the nucleus and the dna is contained within the nucleus nucleus is also where transcription is going to occur so rna polymerase is going to come in it's going to read the dna and it's going to synthesize a complementary mrna mrna is going to exit out the nuclear pore so here's our nuclear pore the yellow is the rna it comes out of the nuclear pore it attaches to a ribosome if that protein is going to be secreted for example that ribosome is going to attach to the endoplasmic reticulum and it's going to synthesize the endoplasmic reticulum or synthesize the protein into the lumen of the endoplasmic reticulum and the protein is going to be folded and processed and then packaged off in a transport vesicle and it's going to leave the rough er in a transport vesicle transport vesicle is going to travel along it's going to fuse with the golgi apparatus golgi apparatus again it's the ups center it's going to package finish sort and ship and so it's going to ship off that protein which it's going to leave as a transport vesicle transport vesicle is going to move along it's going to fuse with the cell membrane and eventually the protein will be released out of the cell and so this is a summary summarizing the protein production pathway so question for you place the following structures in the order they would be used in the production and secretion of a protein and indicate their function so this will be part of the discussion for class on zoom so your options are golgi apparatus nucleus plasma membrane ribosome transport vesicle and rough er so you're going to need to put these in order and then also indicate the function of each of these a hint is that one of these can be used more than once that's my hint so you need to put these in order and list their function and then in the discussion we will discuss the answer to this so question cells need large amounts of ribosomal rna to make proteins the ribosomal rna is made in a specialized structure known as blank which is found in blank is it red chloroplast cytosol yellow ribosome cytosol green endoplasmic reticulum the nucleus blue nuclear envelope the nucleus or purple nucleolus in the nucleus so pause your video think about what you want to say and when you're ready push play if you said purple you are correct the nucleolus and the nucleus so the ribosomal rna is synthesized in the nucleolus and the nucleolus is within the nucleus and again this is where the ribosome will also be um the ribosome will also be assembled so now we're going to move on and talk about other eukaryotic organelles cells do so much more than simply produce proteins and so we're going to walk through the other organelles in the cell and talk about what those other organelles are used for and so we'll talk about the smooth endoplasmic reticulum we'll talk about the lysosome vacuoles mitochondria chloroplasts and the cytoskeleton so the smooth er is rich in metabolic enzymes and there are large proportions of smooth er in specialized cells so the cells in your body that are going to have a lot of smoothie are one place would be in the gonadal tissue so what that means is in testes for male or in ovaries for female because in those gonadal tissues that is where steroid hormones are produced so for example testosterone and estrogen and so the smooth er plays a role in the synthesis of lipids that's one of its functions and so the gonads is going to have a lot of smooth er in it because it's going to produce those steroid hormones liver cells are also going to contain a lot of smooth er and that's because two of the functions of the smoothie are is one metabolism of carbohydrates and two detoxification of drugs and poisons and both of those are achieved by the liver so if you recall back to our macromolecules glycogen glycogen is a storage form of sugar for animal cells and glycogen in animals is stored in liver and muscle and so that that glycogen is stored in liver and muscle and it's stored so that if you let's say haven't eaten in a while and your blood sugar starts to drop your body's response is going to be to break down that glycogen and release the glucose so that your blood sugar goes back up so in the liver the smooth er has a lot of this smooth er so that it can break down that glycogen the other reason it's in the liver is that the liver is also used to modify toxic substances so different chemicals that might be harmful the liver is there to detoxify those drugs and poisons and that happens again in the liver cells smooth er is also abundant in muscle cells again also due to the fact that it helps to metabolize carbohydrates so breakdown of glycogen additionally it's present in muscle cells for calcium sequestration so basically for regulation of calcium stores because muscle contraction uses calcium ions so this would be a class paper that we would do frequent exposure to alcohol leads to decreased sensitivity which alcohol induced changes in the er might contribute to tolerance so what that basically is asking is if you are old enough and you you've experienced this you might know that the more often you drink the more alcohol it's going to take to get you to become intoxicated so somebody who doesn't drink at all might become intoxicated after just one drink somebody who drinks often might need you know five six seven drinks to become intoxicated that's referred to as tolerance so what do you think the cells might do in response to exposure to alcohol that might lead to tolerance so think about what we've talked about in terms of what cells can do for demand and that might help you to answer that question the second part of that question is how might this contribute to tolerance to other drugs that have not been chronically used and what that means is that for example if somebody is an alcoholic and they drink heavily for a long time that same person not only has built up tolerance to alcohol which is the substance they've abused but they might also be tolerant to other drugs that they have not been using so for example when an alcoholic goes for surgery and they're given barbiturates to try and put them under anesthesia in some cases alcoholics are more difficult to put under because they also have built up tolerance to barbiturates even though they have not used those same chemicals themselves so i want you to think about this and i want you to come up with your answer and then again in our zoom meeting we will talk about the answer to this question the next organelle that we're going to talk about is going to be the lysosome and the lysosome is like the recycling center or the cleaning crew of the cell the lysosome is responsible for digestion digestion of a variety of molecules or even organelles the formation of the lysosome is such that it's actually synthesized in the rough er so again it's basically going to be this vesicle and this vesicle is going to contain digestive enzymes which are proteins and so that is going to be synthesized in the rough er and then it's going to fuse with the golgi and in the golgi the lysosome or the enzymes are going to become activated and the lysosome is going to bud from the trans side and instead of that vesicle going to the cell membrane to be excreted instead that vesicle is just going to stay in the cell and now it's an organelle and so the lysosome is actually derived from the endomembrane system so what does the lysosome do well the lysosome itself that digestive vacuole can fuse with a food vacuole and so what that means is that when the cell takes in food the food is going to come in through a process called endocytosis and you're going to learn about that later on food comes in it's packaged in a food vacuole lysosome is going to fuse with the food vacuole lysosome contains enzymes that's going to break down that food lysosome is also used to recycle damaged organelles so if an organelle gets worn out and old the mitochondria for example lysosome is going to fuse with that that old organelle and it's going to break it down and then lastly the lysosome can fuse with what's called a phagosome to destroy foreign invaders remember in that video that i showed you of the white blood cell chasing the bacteria notice that when the white blood cell got to the bacteria you heard the video go num nom nom nom that was basically the white blood cell doing phagocytosis it sent out extensions it engulfed the bacteria and it took it in that bacteria is going to come in in a structure called a phagosome that phagosome is going to fuse with the lysosome and the lysosome is going to break down that bacteria and destroy that foreign invader now there are several genetic disorders that are associated with lysosomal disorders one of them is going to be tay sachs disease and tay sachs is a genetic condition it is recessive so that means you have to inherit two bad copies of this gene in order to have it and tay sachs is when you're missing an enzyme in lysosomes that breaks down lipids so that enzyme is defective and patients who have tay sachs can't metabolize lipids as a result lipids accumulate in the brain which leads to mental and physical deterioration and children usually become blind deaf and unable to swallow and usually die by age four and so it's a very severe disorder um and it's again associated with an enzyme that's defective in the lysosome they cannot metabolize and break down lipids and lipids build up to toxic levels now for sachs tay sachs is more prevalent in certain populations so if you are of that um european jewish descent that would be more common to be the carrier of tay sachs and that's actually something that doctors can test for when you're pregnant they can test you to see if you are a carrier of tay sachs for females and if you are a carrier then your partner could be tested and if they are also a carrier of that gene then the child has a chance of having tay sachs if you're not a carrier there's no way that you're ever going to have a kid that has tay sachs so that is a genetic disease there's another one that's called neiman pick disease it also causes a lipid accumulation so again it's also a problem with the lysosome but in the spleen the liver the lungs the bone marrow and the brain and so this would just be an example of a disease that is associated with problems with the lysosome next we have our central vacuole and our central vacuole is made up of primarily water but you can see that it occupies a large portion of the space inside the plant cell and the function of the vacuole is that it's used to store organic nutrients such as proteins in seeds it also contributes to plant growth by absorbing water and causing the cell to expand because you'll see in the next chapter that we have what's called trigger pressure when water goes in it causes the cell to expand which is what allows the plant to stand upright in flower petals the central vacuole will contain pigments to attract pollinating insects because different insects are attracted to different color flower petals and so that pigment is used to help attract pollinators and it may contain poison to protect against plant-eating animals so to deter animals from eating it now just a reminder the central vacuole is a plant-specific organelle whereas the lysosome is an animal specific organelle so these are exclusive to one cell type or the other they're not found in both next we're going to move on and talk about mitochondria and chloroplasts mitochondria are going to be the power plant of the cell this is responsible for energy it is the site of cellular respiration which is basically going to be to extract energy from organic molecules so this is how your cells are going to break down the food that you eat and they're going to use that glucose and break it down and produce atp atp is cellular energy and so this is where the bulk of atp gets produced in eukaryotic cells mitochondria are found in all eukaryotic cells there are a few exceptions to that there are a few cell types that do not contain mitochondria but that is very unique otherwise we can say as a general rule mitochondria are found in eukaryotic cells they are semi-autonomous they what that means is they can replicate independently of the cell dividing they're not part of the endomembrane system they do contain their own dna and their own ribosomes which means that again they can make some of their own proteins they can grow and reproduce within the cell again independently of what the cell is doing and so that's why we say that they're semi-autonomous in terms of mitochondria having their own dna for a long time the conventional thought was that only the mom contributed mitochondria however there has now been more recent evidence that suggests that in fact fathers do contribute some mitochondria to the offspring it's not only the females but usually if if a child inherits a defect in their mitochondria it affects the way that they produce atp for energy there can be few or many in the cell and again that is dependent on the cell's level of metabolic activity the more metabolically active the cell is the more mitochondria they're going to have so this is showing you the structure of the mitochondria because this is going to be important when we start to learn about cellular respiration so mitochondria has a two lipid bilayer membrane it has a smooth outer membrane so that's here this outer membrane and an extensively infolded inner membrane that's referred to as the cristae and remember that i talked about that structure and function are related and so the reason that the inner membrane has these extensive infoldings is that it increases surface area to put more proteins in that membrane to maximize atp production and so that's why it has this particular structure where it has this increase in surface area as a result of this two membrane system it ends up creating two compartments within the mitochondria and the first part is going to be the inter membrane space and this is going to be the space between the outer membrane and the inner membrane and so that is called the inter membrane space the space inside the inner membrane is referred to as the matrix and so this is an overall overview of the structure of mitochondria so next we're going to look at the chloroplast and the chloroplast is an organelle found in plants and algae and it is the site of photosynthesis photosynthesis is the process of converting solar energy into chemical energy meaning that the plant is able to harness the energy in the sunlight and convert it into chemical energy in the form of glucose and then that plant can utilize that glucose in their mitochondria and use that glucose to make atp for energy so again the chloroplast is what allows plant cells to be autotrophs self-feeders they're able to produce their own food remember that the chloroplast is found in plant cells and not animal cells and so this is why for animals we have to consume our food just like the mitochondria the chloroplast is a semi-autonomous organelle again it's not part of the endomembrane system they contain their own dna and their own ribosomes so they can make some of their own proteins and they grow and reproduce within the cell independent of the cell so it doesn't have to wait for the cell to divide in order for the organelle to divide they are semi-autonomous so if we look at the structure of the chloroplast it is surrounded by two lipid bilayered membranes an inner and an outer membrane and it has a third set of membranes inside that are what are called the thylakoid membranes and these are interconnected membrane stacks and they look like stacked poker chips and collectively we call those stacks of the thylakoid membranes they're referred to as granum now because we have three membranes in this case that creates three important spaces each within a particular function and when we talk about photosynthesis you'll see why these different compartments are important so the first compartment that this creates is what's called the inter membrane space so again it's the space between the inner and the outer membrane so it's that space in between the space inside the inner membrane but outside of the thylakoids is what we call the stroma so the stroma's the space inside the inner membrane but outside of the thylakoids the space inside of the thylakoid membranes is referred to as the thylakoid space so that's the innermost part of the chloroplast now it is believed that both mitochondria and chloroplast were formerly small prokaryotes that began living within larger cells and that theory is referred to as the endosymbiotic theory so the endosymbiotic theory is again that in essence these mitochondria were once a free living prokaryote and that was engulfed in an early cell early on and that prokaryote lived within the cell because it gave both cells an advantage the eukaryotic cell and the prokaryotic cell which would now be the mitochondria both got an advantage the eukaryotic cell got the advantage it was able to extract more energy the prokaryotic cell gained an advantage because it had all the benefits of being protected by the eukaryotic cell and it got other things from the eukaryotic cell as well same thing with the chloroplast it's believed that we had this non-photosynthetic eukaryote meaning it already had mitochondria and then it also acquired a photosynthetic prokaryote and that eventually gave rise to the chloroplast there are several reasons that this theory is believed one is that if you notice they have a double membrane system it's believed that for example in the mitochondria the inner membrane was essentially the cell membrane of the prokaryotic cell the outer membrane of the mitochondria was derived when it was engulfed by that eukaryotic cell and that actually makes sense you'll see this when we talk about cellular respiration one of the things is is that in prokaryotic cells they do not have mitochondria and so you might think well if they don't have mitochondria can they do cellular respiration answer is yes they can still do cellular respiration the difference is for the electron transport chain the electron transport chain in prokaryotes instead of happening happening in the inner membrane of the mitochondria prokaryotic cells don't have mitochondria so their electron transport chain happens in their cell membrane notice that when this this early prokaryotic cell was engulfed by the eukaryotic cell what was now the cell membrane of the prokaryote which is where the electron transport chain happened is now the inner membrane in the mitochondria which is what it is now so that makes sense with this theory that they were once free living prokaryotic cells there are numerous other reasons that they were believed to have been prokaryotic cells at one point one is that remember i said mitochondria and chloroplasts both have some of their own dna if we look at their dna their dna is circular remember that the dna inside of our cells is linear so this structure has circular dna like bacteria and in fact when we compare the sequences the sequences are actually very similar to bacteria as well so that's one reason they're believed to have been free living prokaryotic cells the other thing is that remember mitochondria and chloroplasts have some of their own ribosomes they have 70s ribosomes just like bacteria do remember that your cells use ads ribosomes they are self-replicating like bacteria so again they can reproduce on their own independent of the cell dividing they are the same size as bacteria they're about one to two micrometers in size and they use a type of ribosomal rna called 16s ribosomal rna like bacteria so there are a whole host of reasons that it's believed that those two organelles were once prokaryotic cells and there's a lot of evidence to suggest that to be true so question for you many antibiotics work by blocking the function of the ribosomes therefore these antibiotics will red block dna synthesis yellow block rna synthesis green block protein synthesis blue prevent the movement of proteins through the nuclear pore or purple make the two nuclear membranes fuse into one and so this question is asking which one will happen directly directly so pause your video think about your answer and then when you're ready go ahead and push play so if you answered this question the correct answer would be what color green it would block protein synthesis because remember that the ribosome is responsible for protein synthesis now notice i had to say directly because down the road it would also block dna synthesis and rna synthesis in that those processes are facilitated by proteins so if you didn't make proteins if the cell didn't make proteins eventually those processes processes would stop also but this question is asking if you block the function of the ribosome so directly it would affect blocking protein synthesis so next we're going to move on and talk about the cytoskeleton the overall functions of the cytoskeleton is that it provides mechanical support and maintains cell shape it's also used for cell motility and movement it helps to position organelles within the cell so that they're not just free suspended in the cell and it acts as tracts on which motor proteins travel and so here are some examples of these functions so again you're looking at this sperm here and it has this whip-like tail extension that's called a flagella and that is used for motility or movement if we look over here this purple this is a microtubule which is a type of cytoskeletal element and attached to this would be its motor protein in the case of microtubules there are two motor proteins that are used there's what's called dynein and kinesin and these motor proteins help dictate which direction transport occurs meaning will it go more towards the inside of the cell or is it going to go towards the external towards the edge of the cell the way that these motor proteins work so notice this little orange ball here this is a transport vesicle so you might recall that when the protein leaves the rough er and it goes to the golgi it's transported between organelles in a transport vesicle how does that transport vesicle go from the rough er to the golgi well that transport vesicle is going to bind to this motor protein and this motor protein has these little feet and they walk along the microtubule they use the power of atp and they walk along the microtubule and they take it to the next part in the cell so from the rough er to the golgi for example in terms of mechanical support and maintenance of cell shape you can think of these as like steel beams in a building right it's like this framework that gives the cell mechanical support and maintains cell shape so i just wanted to show you this little clip this is just to show you that the cytoskeleton is very dynamic and what that means is that it's not static it doesn't stay the same these cytoskeletal elements are constantly growing and shortening and growing and shortening and so what you're going to be seeing in this is that they fluorescently labeled microtubules and then using a fluorescence microscope you can monitor and see how the microtubules change over time i did this as an undergrad when i worked on drugs that were used for chemotherapy several of the drugs that we worked on targeted microtubules and so we wanted to see how they affected microtubules and so we would treat the cells with that drug and then look at the activity of those microtubules did it have an effect on how those microtubules moved so let me show you this so you can see this and so you can see these microtubules growing and shortening so let me play it again for you so they are very dynamic and they're constantly changing and this is used for a variety of purposes it's used for movement or mortality which you'll see in a little bit it's used to transport things within the cell but the take home from this video is just to show you that in fact the cytoskeleton is very dynamic while you think of it as being steel beams what you have to realize is steel beams are the same these are constantly changing so there are three main types of cytoskeletal elements we have our microtubules our microtubules are the largest of our cytoskeletal elements and they are arranged they are these tubulin proteins arranged in a circle like a tube so they are these alternating alpha and beta tubulins arranged in alternating order and they create these hollow tubes if we look at fluorescently labeled microtubules you can see these green those are the microtubules the blue is the nucleus and so you can see that these microtubules are all throughout the cell if we look at the intermediate filaments they are intermediate in size so they are the middle in terms of their diameter and these are these fibrinous proteins that are coiled together so they are these coils if we look at the intermediate filaments again you can see them throughout the cell they're heavily concentrated around the nucleus as well and lastly we have our microfilaments which we also refer to as actin and our microfilaments are made of these twisted actin proteins this has the smallest diameter of the three cytoskeletal elements and again it's kind of distributed all throughout the cell and we're going to talk about what are the functions of each type so first one we'll go from smallest to largest microfilaments or actin the structure again is that they are a twisted double chain of actin subunits and the functions of actin first cell shape for structural support that's true actually for all of our cytoskeletal elements actin is also used for muscle contraction it works with its motor protein myosin to help muscles contract actin is used in a cleavage furrow for cell division so when an animal cell divides you're going to see that it's going to form a cleavage furrow and it's going to pinch off to divide the cell into two and that cleavage furrow is because of actin and then we have what's called amoeboid movement and that is some movement and capture of prey by forming rapidly in the direction of movement and decomposing rapidly at the other end so basically the actin filaments being dynamic that is going to play a role in movement because it needs to change constantly in order for the cell to move you saw an example of this when we saw the video of the white blood cell chasing the bacteria the reason that the white blood cell was able to do that crawling motion is because of this amoeboid movement because of actin filaments the actin those are contractile they contract and that pushes the cytoplasm and it causes the cell to move forward so here are some examples of our microfilaments so again we have the pseudopodia these extensions that they send out the submacrophage and this macrophage is sending out this extension and it's going to engulf this bacteria this other example this one we already saw the white blood cell chasing the bacteria that crawling that amoeboid movement is due to microfilaments and then lastly we have our cytoplasmic streaming and so what you can see is you can see that the chloroplasts are moving within the cell and that is again due to actin causing the cytoplasm to move around and so this would be our actin filaments next we have the intermediate filaments the structure is that the diameter is intermediate to microfilaments and microtubules twisted chain and the function of the intermediate filaments is that they're used for maintenance of cell shape and stabilization of the position of the nucleus and other organelles within the cell so they form this kind of mesh around the nucleus which helps to keep the nucleus in its position so again it's to keep the organelles from just free floating within the cell and then lastly we have our microtubules and the structure of the microtubule is again it's a hollow cylindrical rod made of tubulin dimers and so the function of microtubules cell shape because again all cytoskeletal elements function for that purpose movement of vesicles chromosomes and organelles so again if we're trying to move transport vesicles from one place to another it would be along microtubules notice chromosomes this is why drugs that are used in chemotherapy some of them are microtubule targeting drugs because if you can inhibit microtubules from being dynamic meaning from growing and shortening if you can block that from happening that can prevent the cell from dividing because the microtubules are responsible for moving chromosomes in the cell if the microtubules can't move if they can't grow and shorten they can't move the chromosomes in the cell if they can't move the chromosomes the cell can't divide into two so this is why certain drugs like toxol for example those are drugs that target microtubules and these were the types of drugs that i studied and i would actually watch videos of these fluorescently labeled microtubules to see how the drug affected the dynamics of those microtubules microtubules are also used for motility or mobility basically for movement and that's because cilia and flagella are motility structures and they are made of microtubules so again this is just showing you that these motor proteins the dynein or kinesin they will walk along the microtubule so basically the microtubules act as these tracks and the motor protein walks along and it moves the transport vesicle within the cell now cilia and flagella both consist of microtubules and they are made of the protein again tubulin so microfilaments are made of actin microtubules are made of the protein tubulin microtubules are arranged as nine pairs in a ring plus two microtubules in the center what we call a nine plus two array so you'll notice that we have these doublet microtubules they're side by side there are nine pairs and two central microtubules and this allows the flagella to move in a wave-like manner so if you've ever seen video of sperm swimming for example you've seen that it moves in this kind of undulating or wave-like motion that's actually different prokaryotic cells can also have flagella but when prokaryotic cells have flagella they're not made of microtubules and they don't move in a wave-like manner in prokaryotic cells they spin in a circular motion but that's different we're talking it here about eukaryotic cells eukaryotic cells they use microtubules and it has these doublet microtubules these two microtubules side by side and in between them we have motor proteins and those motor proteins cause contractions so it causes those microtubules to slide against one another and that's what causes that wave-like motion if we look at cilia cilia extends from the cell in great numbers meaning that they're generally covering the surface of the cell and they serve to move the cell or to move material around the cell so they're used for motility or to move things around the cell cilia are present in the nose to detect smells cilia are also present in the lungs to sweep the lungs clean of whatever foreign material the body has inhaled and so this is why smokers somebody who smokes cigarettes for example when you smoke cigarettes that damages the cilia that line the respiratory tract and what ends up happening is is when that cilia is not working properly it's not able to move things out of the lungs appropriately and as a result people will end up with what they call a smoker's cough they will cough because that irritation in the lungs is caused by the cilia not being able to clear foreign things out of the lungs cilia are also used in the reproductive tract so in females cilia is in the fallopian tubes and they function basically to help move the egg from the ovary down to the uterus where it would implant if it's fertilized and so the cilia basically beat back and forth and it helps propel the egg from the ovary down to the uterus now one of the things about the way that cilia move cilia move more like an ore so you can imagine if you were rowing a boat and you had an ore that's the type of movement that cilia uses and so what i'm going to show you is a little animation that's showing this paramecium which is a protist and it has these little tiny hair like extensions the cilia that help them move in addition the paramecium also has a contractile vacuole within it that also helps but i wanted to show you that it moves so if you look very closely you can see these little teeny tiny hairs and they're beating back and forth to help the paramecium move now while cilia are numerous and very short projections flagella are relatively long tail-like extensions of some cells that function in cell motility or movement for example in sperm it is sometimes the case that several flagella will sprout from a given cell but often there is a single flagellum it's much more common to have a single flagellum than it would be to have multiple prokaryotic cells have again a different structure in terms of their flagella and as a result they're more likely to have multiple flagella but typically in eukaryotic you're going to see one single flagellum it's not usually multiple the top picture is just showing that flagellum and sperm the bottom is a little video that i wanted to show you that just shows you that the tail that flagellum actually has some of its own energy stored in it it has some of its own atp stored and what you're seeing is there actually severing um the tail or the flagellum of the sperm and you'll notice that even when it's detached from the head of the sperm it still continues to move for some of the time because it has some of its own energy so it's broken and you can see that the tail is still moving that flagellum is still moving even though it was separated from the head of the sperm so if we compare prokaryotic and eukaryotic flagella there are several differences between them the first is that eukaryotic flagella is covered by an extension of the cell membrane and is approximately 10 times thicker than a prokaryotic flagella flagellar movement is different in prokaryotic versus eukaryotic in eukaryotic cells the movement is undulating or wave like but in bacteria or prokaryotic cells the flagella rotates in a circular motion again kind of like a propeller for a helicopter eukaryotic flagella is made of tubulin that's the protein that makes up the eukaryotic flagella prokaryotic flagella is made of the protein flagellin and so these are some of the differences between prokaryotic and eukaryotic flagella so this is just showing you how the cytoskeleton is localized in the cell so the blue are going to be the microtubules the orange is the nucleus the green are the intermediate filaments and the red are the actin filaments you'll notice that the microtubules and the actin are pretty much all throughout notice you can see kind of this accumulation at the edge as well and that accumulation at the edge as well is is used for that amoeboid crawling movement the intermediate filaments in this case are more concentrated right around the nucleus and again that's because the purpose of those filaments is to hold the nucleus in place so question for you suppose that a cell could be seen to lack intermediate filaments which of the following would be the most likely effect of this condition red an inability to get energy out of food yellow an inability to manufacture proteins green a tendency for the nucleus and organelles in the cell to drift around inside the cell blue and inability of the skeletal muscles to contract or purple and inability to move proteins from one part of the cell to another so pause the video think of your answer and then when you're ready push play so if you said green you are correct a tendency for the nucleus and organelles in the cell to drift around that would be because of the intermediate filaments red says an ability inability to get food out of energy that's not true for the intermediate filaments what organelle is responsible for getting energy out of food and the answer is mitochondria right and so that's not the job of the intermediate filaments yellow and inability to manufacture proteins again that's not the job of the intermediate filaments that is the job of the ribosome blue an inability of the skeletal muscles to contract that is not intermediate filaments that is going to be the actin or microfilaments purple an inability to move proteins from one part of the cell to another that is not true that is for microtubules intermediate filament's main job is to keep the nucleus and other organelles in their place and so the last part of this lecture is going to be looking at external structures so just like prokaryotic cells can have glycocalyx so can eukaryotic cells and this is an outermost layer that comes into direct contact with the environment and in eukaryotic cells it's composed of polysaccharide remember that we talked about for bacteria it's usually polysaccharide but can be polypeptide in eukaryotic cells it is polysaccharide and it appears as a network of fibers a slime layer or a capsule and the purpose of the glycocalyx is that it contributes to protection adherence meaning it makes it sticky as well as signal reception meaning how cells communicate with one another next we have our cell wall and in eukaryotic cells our cell wall is found in plants algae and fungi now plants and algae right the cell wall is going to be made of cellulose we're not going to talk much about that here because in micro we don't talk much about plants and algae but we will discuss fungi so for the cell wall of fungi it is rigid and provides structural support and shape it's different in chemical composition from bacterial and archaeal cell walls it's a thick inner layer of polysaccharide fibers that are composed of chitin or cellulose most commonly cellulose and then it has a thin outer layer of mixed glycans so meaning a mixture of sugars so what you're seeing here is the cell membrane here's the layer of chitin it has this glycoprotein a mixed layer of glycans or sugars and then this glycocalyx right which is also sugar-based and then that's the outside of the cell and so the cell wall in fungi is different than the cell wall in prokaryotic cells because again if we talk about bacteria their cell walls are primarily peptidoglycan it's a mixture of protein and sugar in the case of fungi it's primarily sugar-based right it's polysaccharides and so this is the cell wall in fungi in terms of the cell membrane so the cell membrane is a typical bilayer of phospholipids in which protein molecules are embedded in it this is what we refer to as the fluid mosaic model and the fluid mosaic model states that the membrane is a fluid structure with a mosaic meaning a variety of different proteins embedded in it and attached to it now in eukaryotic cells the cell membrane is also going to contain sterols or cholesterols of various kinds and this is going to serve several roles it's going to provide relative rigidity that gives stability to the membrane so basically it's going to act as a patching substance that maintains the correct fluidity meaning it's going to make it so that the membrane is not too liquid and not too solid but is somewhere in between and so steriles are going to help regulate the fluidity of the membrane steriles are especially important in cells that do not have a cell wall so animal cells for example don't have a cell wall and therefore steriles play an important role in this we did see an example of a bacteria that has sterols in their cell wall and that was mycoplasma remember that mycoplasma for bacteria is a genus of bacteria that lacks a cell wall and as a result it has sterols in it in its cell membrane to help regulate the cell so steriles definitely play more of a role in cells that do not have a cell wall they have a very important function the cytoplasmic membrane serves as a selectively permeable barrier it's going to be able to regulate what goes into and out of the cell and so it's a selectively permeable barrier it separates the living cell from the non-living environment so this is just a summary of the general categories that we can break our organelles down into so the first category is going to be our genetic control and we have our nucleus and our ribosomes i'm not going to review the functions what they do you can go back and review this on your own but i just wanted to put this here as a summary slide for you to kind of see in a summary format what these various organelles do we have other organelles that are involved in the manufacturing distribution and breakdown so we have our rough er our smooth er our golgi our lysosome our vacuoles and peroxisomes which we didn't talk about our next category is our energy processing that's going to happen in mitochondria and chloroplast and so those would be involved in energy processing and then the last category would be our structural support movement and communication so that includes our cytoskeletal elements it includes the cell membrane which is going to be our next topic it includes the extracellular matrix cell junctions cell walls and plants etc so i have a video just summarizing all the structures in an animal cell for you to see it all together and so this hopefully will summarize everything that you've seen 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 tracks 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 informings 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