Tuesday, May 24, 2022

9th Grade Freshmen Biology Cell Notes : Prokaryotes vs Eukaryotes

How's it going today we're going to talk about cells specifically the differences and similarities between prokaryotic cells and eukaryotic cells now the air conditioner is a little bit loud in the background and occasionally these doors beep for security we're just going to ignore that and get on into the lecture today .

So first of all what is a cell okay so a cell is the basic unit of all living things it's considered the basic unit of life because it is the smallest unit that's capable of carrying out life's processes by that i mean things like reproduction metabolism things like that you might have thought that an atom is the smallest thing an atom is a very .

Small small thing right but cells are the only the smallest unit that are capable of exhibiting all of life's properties that's why a cell is the basic smallest unit of life so in our organisms we can have unicellular or multicellular varieties if you are unicellular you only are one little tiny cell so this is like a .

Bacteria an amoeba a lot of different protists like a unicycle is one wheel this is one cell unicellular okay and alternatively you can be multicellular and multicellular organisms have multiple or many cells so things that you can see with the naked eye your bare eye without a microscope those things are .

Multicellular plants animals a lot of fungi things like that you can see them so an organism can be unicellular or it can be multicellular so there's two main types of cells and we've been talking about this in class but the two main types of cells are prokaryotic cells or eukaryotic cells so everything that's alive and made of .

Cells contains one of these cell types there's no other types it's either a prokaryote or it's a eukaryote and the word prokaryotic literally means before the nucleus technically before the kernel but they're referring to the nucleus as the kernel okay so pro means before and karyotic is referring to the nucleus .

For eukaryotic organisms u means true so this contains a true nucleus or a true kernel okay we're going to talk about robert hooke a very long time ago 1665. he observed cork cells under like the first makeshift microscope okay so here is his drawing when he was observing cork cells .

Now cork is a plant and as you can see it's very compact in the brick-like structures that we're used to seeing associated with plants and he called these little cells cells because they reminded him of prison cells how it was very like blocked together like little rooms all next to each other that's what he .

Thought they looked like so he called them cells today we still use that terminology the cell is the basic unit of life so he kind of led the way for the discovery of the cell theory okay the cell theory was a combination of a whole lot of scientists working together but it has three major .

Components the cells are the basic unit of life so like i said they are the smallest unit capable of carrying out life's processes cells are the basic unit of life all living things all organisms are made of cells so from the smallest little bacteria up to the largest mammals on the planet .

They're all made of cells and lastly new cells are produced from existing cells so in other words cells come from cells this just means that cells don't rain down from the sky they don't appear out of thin air they come from other living things this makes sense through reproduction cells come from other cells .

So as i said there are two main types of cells so we'll talk about the discovery of cells prokaryotic and eukaryotic those are the two main classes prokaryotic we talked about how it literally means before the nucleus these were the first primitive cells to evolve these were the very first simple little organisms as you can see there's a .

Picture here of a prokaryotic cell it's very simple okay this is just a little oval shape it's got a few things floating around in it most likely those are ribosomes okay and then it has free floating dna because it doesn't have a nucleus it literally means before the nucleus so if it came before then it can't have a nucleus right .

So prokaryotic is before nucleus they are the first primitive cells and as i said they don't have a nucleus so eukaryotic means true nucleus we just talked about that so as you can see from this little green guy over here we have a defined nucleus and now we also have something called membrane bound organelles this means that these .

Organelles contain membranes around the outside of them so eukaryotic cells evolved after prokaryotic cells the theory is something called endosymbiosis which means living in harmony one inside the other essentially okay so the theory is that one .

Prokaryotic cell ate wrapped around and ate another prokaryotic cell and that's how we got the first primitive eukaryotic cells that's why all of these organelles have a membrane inside of them so first to evolve is prokaryotic because it means before the nucleus and second to evolve is a eukaryotic cell .

Because it came after our prokaryotes because supposedly they have engulfed each other they've eaten each other and become living together here that's where we have all these membrane-bound organelles coming from that is eukaryotic so they came later so let's talk a little bit more about .

Eukaryotic cells so eukaryotes all have a nucleus with a nuclear envelope this just means that there is a membrane around the outside of the nucleus they are much larger and very much more complex than prokaryotes as you can see in the image here we have a lot of things going on .

And this isn't even all of the organelles that are inside okay next we have membrane bound organelles as i was saying before so we have the golgi body we have the endoplasmic reticulum we have lysosomes we have vacuoles we have a nucleus okay there's a lot of things going on inside of our eukaryotic cells .

Okay that's only a couple of the different organelles and as you can see here like i said that's only a couple of the different organelles that are inside of eukaryotic cells but remember that each one of these organelles has a membrane around it these are membrane-bound organelles okay .

So that's basically in order to separate that organelle from everything else inside the cell if you think about your body your body has a lot of organs in it right and your organs make up your organ systems which you know make up an organism so if you think about this on a really really small scale .

Our eukaryotes have organelles inside of them and these organelles kind of act like our organs that each one has a different job in order to keep the cell functioning correctly that's exactly the same thing as our organs they're all functioning to keep us function they're all working to keep us functioning .

Correctly right that's exactly what's going on just on a very very small microscopic scale okay eukaryotes also have dna it is double stranded and it forms chromosomes it is highly organized our eukaryotes can be unicellular from our little protists all the way up to .

Multicellular organisms that can be very very large mammals very very large trees okay for example our eukaryotes are animals plants fungi and protists so those are our four different organisms that fall under the category of eukaryotes here's some images we have a plant and an animal cell to compare here .

So if you think about eukaryotic cells you have a brain your cells have a brain it's called the nucleus okay so if you look at the comparison here we have the plant on the left and we have the animal on the right so you can see that our plant cell has slightly different structures you can see that it has a cell wall you can see .

These things called chloroplasts inside and you can see that the shape overall is different it's a little bit more um rigid in shape and that's to help plants stand up right our animal cells are more spherical they're more like circles if you were to draw them on a piece of paper .

But you'll notice some similarities like i said you'll notice that they both have a nucleus they both have a cell membrane they have ribosomes they have mitochondria okay so you can look at the pictures here and see some similarities between our plant and animal cells and remember both of these are eukaryotic cells they .

Have a true nucleus as you can see it's the large sphere in the middle of the cells they both have a nucleus they both have membrane-bound organelles they're larger cells so you can take a second to pause this and look at some of the similarities and differences between plant and animal cells .

Next we have this large chart that is the eukaryotic structures in plants and animal cells it has the name of the um of the organelle it has the description for you and then the function what it actually does i'm not going to go through and read every single one of these to you because you guys are completely capable of reading but if .

You'd like to pause and just take a second to remind yourself of some of the major organelles inside of eukaryotic cells this is a place for you to do that so we do have some differences between plant and animal cells they're still both eukaryotic but we do have some similarities and some differences between them so here we'll start off .

With some differences so only plant cells they're eukaryotic but only plant cells have the cell wall around the outside to give them more structure it's a firm wall around the outside of the cell membrane they have chloroplasts and chloroplasts contain a pigment that usually makes plants green .

And that's where photosynthesis happens you know that we as animals do not do photosynthesis but plants do photosynthesis that's how they make their own food and chloroplast is where that magic happens they also have a large central vacuole and that large central vacuole fills up with water and that's what allows plants .

To stand up straight if you've ever seen like your mom get a bouquet of flowers or you get a bouquet of flowers and they start to droop sometimes okay the water or the stems need to be cut so then the water needs to be replaced so the stems need to be cut so then they can get more water into their large central vacuoles you'll also .

Notice that like i live in texas it's extremely hot during the summers when plants start to wilt they need more water to be able to stand up correctly that's called turgor pressure because that large central vacuole soaks up as much water as it can to where it's kind of like a really full water balloon right that it's it's very rigid so now .

It's going to stand up straight that's trigger pressure and that's all because of the water storage and the large central vacuole so those are some unique characters characteristics of plants animals do not have those things but animals do have other things that are special to them so only animal cells have lysosomes .

And centrioles so lysosomes are for waste removal you can kind of think of them like little trash cans so they will go around and collect waste in the cell and then dispose of it and then centrioles are used for cellular division in animal cells there's a similar process that occurs in .

Plant cells but we'll get to those details later when we get into cell reproduction so here's some images of eukaryotic cells you can see that there's a lot of things going on inside of the cells here you can see a paramecium you can see that we have an animal cell that's blue up in .

The top you can see that we have a plant cell that's green okay you can see that we have a cell wall in the plant cell you can see we have a cell membrane in every single one of these cells because every single cell has a cell membrane okay you can see the nucleus and if you want to take a second to pause this and look at the other similarities you can .

Feel free to do that now okay so next we're going to talk about prokaryotic cells so remember that prokaryotes evolved first they do not have a nucleus because the word literally means before the nucleus so they have no nucleus and no membrane-bound organelles they just have ribosomes and ribosomes are technically .

Subunits they're not membrane bound and some people consider them organelles some people don't because technically they are subunits okay all prokaryotes are unicellular this means that all prokaryotic organisms are only made of one single cell .

They are much smaller than eukaryotic cells and they are much simpler than eukaryotic cells this makes sense if they're really really small there's not a lot of room inside of them for all of the crazy organelles and functionalities that come with that as we have in our larger counterparts the eukaryotic .

Organisms okay so prokaryotes are very very small and very very simple they do have dna and it is in a more circular shape and it occurs in the middle of our prokaryote it's kind of floating around in the middle it's not encased in a membrane called the nucleus the way it is inside of a eukaryotic organism .

It's still there but it's just kind of floating around the middle and all prokaryotes are bacteria so we're talking about the types of organisms here it's just bacteria remember when we just talked about eukaryotes we talked about plants we talked about animals fungi and protists but prokaryotes are literally just .

Bacteria and not all bacteria are bad there's a whole lot of them that are very good for us okay so don't give them a bad name for that but prokaryotes are bacteria here's some images these all happen to have flagella which is like the tails that's coming off of them not all bacteria have that but .

Many of the images that you find on the internet do have flagella you can see here that there's a lot of like empty space in the cytoplasm you can see that we have the bacterial dna that's floating around the middle okay and occasionally you'll see pictured ribosomes as well so in class we talked about this pb no .

No pb no no okay that's going to help you remember the important things about bacteria and prokaryotic cells so it stands for prokaryotic bacteria no nucleus no membrane-bound organelles okay so that's a little you know hack for you to remember all of the things you need to know about prokaryotes .

Because if it's not describing a prokaryote it's probably describing a eukaryote so now for some similarities we compared and contrast we did the differences now let's talk about what's similar between prokaryotic and eukaryotic organisms so one they all contain four biomolecules and the biomolecules are .

Lipids carbs proteins and nucleic acids biomolecules means life molecules you know we're talking about cells and cells are the basic unit of life so it makes sense that they would contain all four of the living molecules biomolecules they both have ribosomes they both have dna they both have cytoplasm which is just .

Kind of that jelly stuff that's around all the organelles in the middle of the cell they can be unicellular but remember that eukaryotes can also be multicellular and they all have a cell membrane okay they all have a cell membrane .

Now remember that the cell wall is in plants okay but they all have a cell membrane every single cell has a membrane around it but our plants have a cell wall okay don't forget that they have both implants i put that on here just to remind you of that .

So here's an image directly comparing the eukaryotic cell structure to the prokaryotic cell structure you can see at the top eukaryotes and down at the bottom you've got your prokaryote so again you can see that they are much more complex there's more going on inside the shapes are a little bit different .

And then you can see at the bottom that we have our prokaryote there's free-floating dna that is not inside of a nucleus okay and it doesn't really have a lot of organelles going on like i said it has ribosomes which are technically subunits and remember that all cells have a cell membrane as i was just talking about yes .

Other organisms aside from animals can have a cell wall yes absolutely but they still have a cell membrane inside of that cell wall so the cell membrane is also known as the plasma membrane it's also known as the phospholipid bilayer okay all of those words mean the same thing just like ninth grade and freshman means the .

Same thing a phospholipid bilayer is two layers by means two two layers of phospholipids and that's the major component of your membrane we're to get into a whole lot about membrane and how things are moving in and out of the cell but i just wanted to refresh your memory on this and the phospholipids have a hydrophobic .

And a hydrophilic region this is a water loving and a water fearing region to the molecules the cell membrane contains cholesterol to help maintain fluidity of the membrane which means that it maintains its flexibility and the cell membrane contains proteins for nutrient transport which we'll talk .

About in our next unit and it contains carbohydrates for cell recognition this is how cells can start off it's a start of cell communication how cells can identify one another this is an image of the phospholipid bilayer an image of the cell membrane this is a .

Cross section of it as you can see there's a lot going on here but this is common in every single cell they all have phospholipid bilayers whether it's eukaryotic or prokaryotic so it surrounds every single cell it's selectively permeable which means that it controls what comes in and what goes out and there are two main types of .

Transport called passive inactive that we're going to get into like i said in our next unit so you're asking me we've talked about bacteria we've talked about animals we've talked about plants fungi protists eukaryotic prokaryotic cells okay but we're hearing a lot about a virus especially in today's day and age what .

Is a virus i thought a virus was small i thought a virus was bad i thought a virus was alive well they are in fact not alive they are not cells so a virus is neither of the cell types that we've been talking about because it's not a cell it does not have a membrane it is not a cell they are not alive .

A virus is a special protein and dna subunit that attacks living cells right and it takes over the machinery and that's how it's able to replicate by using host cells so a virus can't do anything unless it gets into a host cell and starts to use that living cell .

To do its bidding so i like to think about viruses as just dna in a pretty package it's just a protein and some dna it's not alive it is not a cell so please don't make that confusion we will get a whole new unit on viruses uh later this semester .

Okay so i wanted to call your attention to one similarity between prokaryotic cells eukaryotic cells and viruses which remember are not cells in this middle portion right here they have one thing in common do you know what it is they all contain dna sometimes viruses have rna .

But they all contain dna that's what you would put in this little section of our venn diagram they all contain dna that is the only similarity between our cells that are living and viruses that are not living so this is where your notes stop but i'm going to go into a question and answer .

A couple of slides here just to help test your knowledge if you want to stop here totally fine i'll see you in the next one if you want to review some of these slides with me i'm going to go ahead and go through those now what type of cells is this and how do you know well when i look at this i see the label .

Of cell wall i see that it's green i see large central vacuoles and i see chloroplasts i know that this is a plant cell what type of cell is this how do you know when i look at this i see something that does not look like a cell .

I see something that says dna and this kind of looks like a cookie robot you know from despicable me looks like a little cookie robot this is a virus it is not a cell and i know this because it doesn't have a membrane or any of the organelles that we've been talking about what type of cell is this how do you .

Know when i look at this i see kind of an oval-y shape i see that we have a nucleoid region which is just kind of scattered dna i see that we have ribosomes but i don't see a nucleus or anything like that so i think this is a bacterial cell or a prokaryotic cell .

Because it's lacking the things i was just talking about which organelles are specific to plants do you remember what they were we have a large central vacuole cell wall chloroplasts here we go which organelles are specific to animals there's two of them do you remember what .

They are it's lysosomes that are used for waste removal and centrioles which are used in cell division why are viruses considered abiotic let's break down that word a means against bio means life .

They are considered not to be alive they are not alive why are viruses considered not alive viruses are not alive because they are not cells and only cells make up living things viruses are smaller than that they contain protein and they contain dna they require a host and they are not .

Alive what characteristics do viruses share with cells viruses that are not alive and cells like prokaryotic cells and eukaryotic cells that are alive all have dna in common all of them have dna or some kind of genetic material what does pb no no mean .

It means prokaryotic bacteria no nucleus no membrane bound organelles that's important membrane bound organelles because remember that they still have the cell membrane they still have cytoplasm and they still have ribosomes which are still technically subunits .

Which cells contain nuclei that's our eukaryotic cells because eukaryotic means true nucleus plants animals fungi and protists all eukaryotes what characteristics do all cells have in common do you remember all cells have our biomolecules .

All cells contain dna all cells have a cell membrane all cells contain cytoplasm and all cells have the capability of being unicellular but remember all prokaryotes are unicellular and some eukaryotes are unicellular what does letter f represent letter f .

This to me looks like a plant cell one it's green two it's got an interesting more rectangular shape it has a large central vacuole and a nucleus so what on earth could those little things labeled f be there are chloroplasts .

What does letter e represent letter e to me looks kind of like a little bean with a squiggle in the middle okay that is our mitochondria that's the powerhouse of the cell because it creates energy for the cell and that brings us to the end of our cell review i hope this was helpful you .

Guys have a great day and i'll see you in the next one

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