Understanding the Structure and Function of the Cell: A Comprehensive Overview

all right ninja nerds in this video today we are going to be talking about the structure and function of the cell

also if you guys haven't already go watch our video where we talk about how i study and prepare for videos within

that i kind of gave you guys a sneak peek of how i pretty much went through studied this topic developed notes

diagrams and then drew it all on the board now we're going to go through it before we get into this video though

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right ninja nerds let's get into it all right an engineer so we're going to take a tour through this cell talking about

what all the structures of the cell are and then what they do so the first thing we got to talk about

is the brain of the cell the pretty much the center of the cell where everything that a cell is kind of really begins in

all centers around and that is the nucleus this is the big mama

the nucleus now what we have to talk about with the nucleus is a couple different components of the nucleus what

are the different components of the nucleus well the first part of the nucleus is as

you can see you see this kind of like blue membrane that's double layered here so you have an outer layer

and then you have a inner layer on this side right so this is our inner

layer these two components make up what's called the nuclear

envelope so you have an outer layer and then you have an inner layer i know that sounds pretty obvious but there's a

different there's different functions for the outer and the inner layers so the outer layer let's actually first

say the nuclear envelope you have two layers the outer layer and the inner layer

what is the purpose of these layers so the first thing that you need to

remember is that the outer layer is where you have lots of ribosomes so ribosomes are

actually going to be kind of found outside on that outer layer the reason why is in the actual nucleus you make

you take dna and convert it into a structure called mrna and mrna has to move out via the nuclear pores and bind

onto ribosomes on these outer membranes which then get moved to the rough er we'll talk about that a little bit later

but that's the big thing i want you to remember about the outer membrane the inner membrane

has a very very important protein structure that binds to the the dna and histone proteins and controls a lot of

cell division it's this green protein here that green protein that lines the inner membrane is called lamins and

lamins are very very important structures that control the structure of the nuclear envelope they're also

important for cell division and interacting a lot with the chromatin there's actually a disorder whenever

there's a mutation in this lamins it causes progerias so it's important that we kind of know these two components of

the nuclear envelope the next thing is in the nuclear envelope you see these red proteins that are dispersed

throughout it those red proteins that are dispersed throughout it these are called nuclear

pores so what are these called nuclear pores and the whole purpose is it's honestly pretty straightforward right if

we want to move things in ions or proteins or nucleotides or different things

in and out of the nucleus that's the function of the nuclear pores and there is things we'll talk about

this a little bit later in a more specific video where we go more in detail on the nucleus but there's

special types of transporters that are associated with those nuclear pores we'll talk about those in other videos

but again another important thing that's a part of the nuclear envelope if you will that actually kind of uh

kind of separates different portions where there's little pores is called these nuclear pores

and again the whole purpose of this is to allow for transport and what kind of transport

transport between the cytoplasm to the nucleus or nucleus to the cytoplasm that's all it is pretty straightforward

the next one is this red diced up structure here called the nucleolus the nucleolus is very very important and

the reason why is this is the site of a particular type of rna synthesis you know there is a particular type of

rna what we call rrna so we're going to denote this as r rna synthesis

this occurs in what structure this occurs within the nucleolus now the reason why that's important is

when you take rrna you synthesize it within the nucleolus and you combine this with proteins so then combine

with other types of small proteins guess what you make you make ribosomes

so really what we can say is is that the nucleolus which is a component in the nucleus is important for making

ribosomes which is made up of rrna and small proteins the last part of the nucleus is all of

these blue structures you see all these blue structures that are kind of dispersed throughout i kind of made

circles around them this is called chromatin this is called chromatin

and chromatin is very very important because this is what really makes up who we are

as kind of humans and it's very important for us to know the different components of chromatin

so within the nucleus you have this structure called chromatin so what in the heck is chromatin chromatin is made

up of two primary things dna and proteins but the main protein

is histone proteins histones these two things make up our actual

genetic material and this chromatin can actually come in two forms two important forms

one is called euchromatin and euchromatine is the loose chromatin and it's the one that's going to be more

for expression of the dna to transcribe the dna and make different types of mrna or undergo replication so euchromatin

should be more in the center of the actual nucleus and the next one here is going to be

hetero the heterochromatin and the heterochromatin is going to be the tight

chromatin this is going to be the chromatin that you're actually going to see

closer towards the inner membrane of that nuclear envelope so we're understanding this right so we

know the different structures and the different components here of the nucleus the last thing that i want us to

understand here is what in the heck does the nucleus do we're going to go into way more detail in this in future videos

but what you need to remember is that chromatin which is made up of dna we can take dna and do a bunch of things with

it what can we do with it we can take dna and we can make more dna

what is this called dna replication i can take dna and make rna

and that is called transcription and then also you need to know that there's different types of rna what are the

different types of rna there is t rna

there is mrna and

r rna so it's important for us to understand this kind of things that are happening

with inside the nucleus which is what you have dna replication and transcription and particularly making of

rna molecules and these are the rna molecules and again we'll go over these in more detail in future videos but this

tells us what the function of the nucleus is and what the components of it are let's move on to the next organelles

okay so the next thing that you guys need to know here is this next filamentous membranous structure that is

located within the cell this beautiful organelle is called the rough endoplasmic reticulum so it's

called the rough endoplasmic reticulum we're going to put e r so the rough er that's commonly how

we refer to it as right so the rough endoplasmic reticulum or the rough er now the rough er if you notice it's this

filamentous kind of network here but there's another structure here called the smooth endoplasmic reticulum

so you have the rough endoplasmic reticulum and then you have the smooth the smooth endoplasmic reticulum

the smooth endoplasmic reticulum and rough endoplasmic reticulum differ in what way this is very simple

you see these little red dots that are located on the rough endoplasmic reticulum

it's called ribosomes so within the rough er this contains

ribosomes on that outer kind of membrane structure on the smooth er there is no ribosomes

that's really it there's nothing much more that you have to know about kind of the structure of the rough er and the

structure of the smoothie are you know that it's an organelle and the big difference between these

structure wise is roughy iris ribosomes smooth the r does not have ribosomes so now the next thing has to come down

to what are the differences in function here that's really where it kind of lays in right

so the first thing we have to do is before we move into what it does we have to kind of pick up a quick point here

from the nucleus and move to the rough er so you know we said within the nucleus

you have dna and from dna you can undergo transcription what is that called

whenever you go from dna to rna whenever i go from dna and i make a molecule

called mrna and that mrna then binds with a ribosome here's our ribosome a little like red

dot there that ribosome will then do what it'll undergo the process of translation

taking the rna and making proteins well what happens is that ribosome it's going to start synthesizing and making

proteins from the mrna so now i'm going to have this protein that gets pushed in here

from the ribosome now that's important because the rough er is obviously going to be a site of

protein synthesis then that's one thing we can say it could be a site of protein synthesis because that's where the

ribosomes are kind of sitting on so that's one function of the rough er so one function of the rough er we can say

is is it's a site of protein synthesis site

of protein synthesis and we're going to talk a little bit

because there's different types of proteins that we make proteins that can be within the cytosol proteins that can

be within different organelles proteins that we can secrete proteins that we can put into the membrane

generally the proteins that the rough er is making is going to be proteins that will become

lysosomes so proteins that will be incorporated into our lysosomes proteins that will go

and get incorporated into the different organelles like the membranes of organelles or the cell membrane

or proteins that will be excreted so that is really the big thing that i

want you to remember about the rough er site of protein synthesis but particularly for these types of proteins

the next thing is what else does it do with the proteins we know what synthesizes them but you know what else

proteins have to fold a particular way for it to be particularly functional so it also helps with the folding

process so it plays around what's called protein folding that's very important

so plays around protein folding and the next thing is not only does it help with folding the protein in a

particular way it also has little enzymes located kind of in this actual endoplasmic reticulum

that can add on little residues little sugar residues onto this protein making it active what is this called it's

called glycosylation so it can perform what's called glycosylation

like cosylation and there's a particular type we'll go into this more in more detail but for the most part it is

called in type glycosylation and all that means is if i

were to take a protein here i took it the mrna took it to the ribosome ribosome bound to the rough er

it made the protein push the protein in the filamentous network of the rough er it started folding and then once we have

that protein here that's folded properly i'm going to just add on a little sugar residue

so this is going to be a little sugar residue and this is going to be my protein

and this is important because this is the way that we activate these proteins so that is the function of the rough

endoplasmic reticulum now the next thing one last thing for this is remember i told you that the site of

protein synthesis for these particular things so in order for after the rough er has

kind of gone through this process of synthesizing it folding it and then glycosylating it it then has to package

it so then what happens is it'll package off so what happens let's

say here's the protein the protein will actually bud into this little

portion of the actual rough endoplasmic reticulum and when it does that that'll actually butt off

and then i have a vesicle and within that vesicle is going to be my protein what protein will become a lysosomal

protein and membrane protein are excreted protein but in order for that to happen i have

to move this towards the next organelle which will be the golgi apparatus we'll get to that one in a second but here's

going to be that protein that was coming from the rough endoplasmic reticulum and moving towards

the golgi so now we know all the functions of the rough er now we've got to go over the functions

of the smoothie are the smooth endoplasmic reticulum this is a very interesting structure so

there's a lot of different types of enzymes located within this smooth endoplasmic reticulum particularly

enzymes that are associated with lipid synthesis that's big thing i want you to take away from this so it's primarily

associated with what lipid synthesis there's going to be a bunch of different enzymes located within these

organelles within this organelle and what kind of lipids are we synthesizing fatty acids

fatty acids are a big one phospholipids are a big one what else you know there's another

really important cholesterol molecule with cholesterol so i kind of give it away so cholesterol and cholesterol is

important because this can become hormones steroid hormones testosterone progesterone estrogen all that good

stuff so this is the big thing i want you to remember is this is the site of lipid

synthesis so we take precursor molecules that we get from the cell let's say here's a precursor molecule

that precursor molecule for the fatty acids phospholipids cholesterol it will get taken up into this smooth

endoplasmic reticulum the enzymes in it will start using these precursors to pop out

little cholesterol or lipid molecules so now from this

we're going to have the smoothie r take the precursor molecules perform the lipid synthesis process with the enzymes

and then butt off a particular vesicle which is going to contain what

fatty acids phospholipids and cholesterol and then guess where we could send this we could all send it

again to the golgi or maybe even send it to the cell membrane and then from the cell membrane we may release out

cholesterol maybe release out fatty acids pretty cool right there's another set of enzymes that are

important here the next set of enzymes is called cyp450 you're like what the heck is that

cyp450 enzymes are very very important for detoxification

so you know whenever your liver your liver has a very high concentration of these enzymes because that's our detox

center right so if you go to your liver there is lots of this enzyme

and the reason why is any drugs any toxins any alcohol you know alcohol ethanol

etoh any of these things have to go to the liver

and what your liver does is is it undergoes a process called biotransformation or xenobiotic

metabolism and it breaks down these substances and it's because of these enzymes

located within the smooth endoplasmic reticulum so it undergoes what's called bio

transformation ba-boom that is important

the next thing here this is an interesting one you know within our cells

we have glycogen right you know glycogen it's basically a a big polymer of glucose and whenever our body needs

energy that glycogen can get broken down into glucose but there's a particular step whenever

you're breaking down glycogen into glucose there's an intermediate between this called glucose 6 phosphate

well in order for glucose 6-phosphate to get converted into glucose guess what it needs

there's a particular enzyme on the smooth endoplasmic reticulum and that enzyme will need to take the

glucose in give a little transporter that'll take the glucose 6-phosphate in and then a

particular enzyme that'll rip off that phosphate on the six carbon of glucose and make off glucose 6 phosphate and

make glucose so the important thing to remember here

is that this actual smooth endoplasmic reticulum is also important for glucose 6-phosphate metabolism so it's also

important for glucose 6-phosphate metabolism

baboon roasted last one last function you know this is a smooth

endoplasmic reticulum it's in in a lot of different organs but you know organs that contain lots and lots and lots of

calcium like in our muscles there's kind of a an analogous structure there called the

sarcoplasmic reticulum these can store lots of calcium and you know there's little pumps that

are located on the smooth endoplasmic reticulum and whenever we need calcium whether it be

for different types of transport processes or for muscle contraction guess what we can pump that calcium out

into the cytosol and utilize it for all these different types of chemical processes so what is the last function

here for the smooth endoplasmic reticulum it also stores calcium

ba-boom all right we've covered the functions of the rough er and the smoothie are let's

now move on to the golgi apparatus all right ninja nurse so what have we established up to this point so we know

that we've understood the function of the rough endoplasmic reticulum we understand the function of the smooth

endoplasmic reticulum and again to kind of go off of that that smooth er again what did we say it could also make

the different phospholipids and cholesterol and different types of fatty acids and that also from the

smooth endoplasmic reticulum can get sent to the golgi now the vesicles that are coming from these

two areas primarily the rough endoplasmic reticulum we're going to focus on from this point but again

realize that everything from the smooth er as well all right so what is the name of this next organelle that we have to

talk about this is a very very important structure called the golgi apparatus right so we're going to call the golgi

now the golgi apparatus is a very important kind of like packaging organelle if you will so it takes these

vesicles coming from the rough er from the smoothie are and when it takes it into the golgi there's an anatomical

term here on this side of the golgi where these vesicles from the rough yarn smoothie

are going to this part of the golgi here is called the cis golgi

okay or they call the cis face of the golgi but we're going to call it cis golgi

then what happens is through these systematic steps these proteins and different types of fatty

molecules that get taken to the golgi will go through the golgi and as it goes through the golgi it'll actually bud off

right so then you're going to butt off some type of molecule in the golgi whether that be a protein whether that

be lipids cholesterol whatever it buds off and then leaves the golgi this side where the vesicles are coming

out of the gold gene going towards lysosomes or cell membranes or whatever this is called the

trans golgi or the trans of the golgi so that's an important kind of

anatomical term or structure component of the actual golgi that you need to know

the next thing here is we have to kind of primarily focus on the function so primary function is it's receiving

vesicles containing proteins and different types of sugar molecules maybe attached to it as

well as different lipids from the rough er and smoothie guard that's the first function so first function that you need

to know here so it's receiving vesicles from

the rough er and the smooth er that's the first thing we know it's receiving the vesicles

containing proteins or fatty molecules now let's focus on those proteins because that's where it's more important

the proteins that are getting taken into the golgi it might have to modify we saw that it

was folded and modified a little bit in the rough er but the golgi might have to modify it even a little bit more and how

does it do that so this modification step is very important and it's again

through a couple different reactions remember we have what's called glycosylation reactions that we talked

about with the roughy are the golgi can do the same thing it can do what's called a glycosylation

but this glycosylation reactions where it adds on sugar residues there's two types one is the n type

and one is o type what's really important to remember is that the golgi is the only one that can

do o type glycosylations in other words i'm adding a sugar residue onto the oxygen component of a protein that's all

it really means in type you're adding a sugar residue to the nitrogen component of the protein

nothing special the other really important step here is it also has to phosphorylate specific

types of proteins and that is very important there's a disease called eye cell disease and it's actually related

to this phosphorylation reaction so that's why we need to know it so it modifies proteins and some lipid

molecules through these glycosylation and phosphorylation reactions the next thing is

is it packages these molecules right

and then after it packages these molecules into their own little vesicles remember how we said that these

molecules will go through the golgi undergo these modifications get stuck into like a little vesicle butt off

and then pop off here it's going to pop off right so now i got my vesicle containing

my proteins and my lipids and all these things that have been modified even more now what happens is

these molecules we already talked about where they're going to go they're going to go

and become lysosomal proteins they're going to go and become membrane proteins or they're going to go and be excreted

out of the cell that is the destination and the function of the golgi apparatus so now we

understand that now that we've done that we have to talk about another little structure here

which is our cell membrane it's another component of the cell all right so the next really really important component

of the cell is the cell membrane so what we're going to do is we're going to kind of zoom in

on a different part here of the cell right which is our cell membrane and there's different components of the cell

membrane so if you look here you see like these little red dots with like little you know fingers hanging out

this is a part of what's called our phospholipid bilayer so when we talk about the cell membrane there's a bunch

of different structures that are involved within the cell membrane and they obviously carry out a very

important function so what are the different components of the cell membrane the first component

here is these little red little thingies what are these little red thingies these are called this is a part of your

phospholipid bilayer so you have two components of it if we kind of zoom out on this little guy

you have these two components this head component of this phospholipid bilayer is actually the phospholipid

and what you need to know about this is that this is polar what does that mean polar means it's water soluble so it's

the hydrophilic portion it can interact with water because it has lots of negative charges

on it the other component here is the little tail this tail these are fatty acids and

fatty acids are really saturated with hydrogen and so because of that they are very non-polar

hydrophobic don't like to interact with water because they have no real negative or slight changes in charge

that's the important thing here so we have this on both sides on the inner cell surface you would have this

phospholipid kind of portion pointing inwards on the outer side you would have it pointing outwards and then you have

the tails pointing in towards one another the next thing is you see this little

green structure which is kind of lodged between these phospholipid

this green structure here is called cholesterol now you're like like what the heck why

is cholesterol coming oh and they even add on here where could that cholesterol come from the smooth er

we packaged it sent it to the golgi and then incorporate it into the membrane we're putting things together ninja

nerds but the cholesterol is also incorporated in there and the cholesterol is important because

it controls like fluidity okay so it controls fluidity all right so again to recap this whole idea of

cholesterol with fluidity again it's just important to remember that the amount of cholesterol if you wanted to

think about like this the amount of cholesterol in the cell membrane the more of it you have

the less space there's going to be between the phospholipids so there's less fluidity so more cholesterol less

fluidity and the less cholesterol you have here the more space there's going to be between the phospholipids and so

there's going to be more fluidity so less cholesterol more fluidity so that's an important concept with that

the next component of the cell membrane so we have the cholesterol we have the phospholipid bilayer the next big

component here is the proteins so the next one that you're going to have here is these little proteins

and these proteins here my pink marker here these proteins there's different types

of proteins there's what's called integral proteins and peripheral proteins

and what is really really important for these proteins is that they have various different functions they can act as

transporters they can act as little enzymes they can act as linker proteins between other cells so they have a lot

of different components a lot of different functions to them but again there is integral proteins and

peripheral proteins the big thing i want you to take away from this

of the cell membrane is that it basically acts as a barrier i mean i know that sounds super obvious

but it is a barrier it's a selectively permeable barrier and only allows for particular types of diffusion that we'll

get into later but there is what's called simple diffusion

right there's what's called facilitated diffusion

and then there's different types of what's called vesicular transport

and all of these types of processes are involving the cell membrane so in other words moving things from outside the

cell to inside the cell we have particular types of processes that we'll have to go into more detail about

but again big thing i want you to take away from the cell membrane is these different components and how it acts as

a barrier for particular types of transport processes all right let's move on to the lysosomes

all right so the next structure here is going to be our lysosomes our beautiful little lysosomes now these are very very

cool kind of organelles

now what lysosomes are important is they're like these little spherical organelles

and they contain very interesting little enzymes inside of them and these enzymes are called hydrolytic

enzymes and really the simplest way of describing these hydrolytic enzymes is

you have different types you have proteases which means that they break down

proteins you have nucleases which means that they break down nucleic acids you have lipases which means they break down

lipids and you have glucosidases which means they break down

carbohydrates so all of these hydrolytic enzymes are located within these little organelles

so why is that important any macromolecules that you bring into

the cell whether that be from a white blood cell undergoing what's called phagocytosis whether that be you

actually undergoing an endocytosis process from uh it's called clathrin-coated mediated endocytosis

that whole process when you're bringing something in you're bringing in particle matter

and these lysosomes are responsible for using these enzymes to break down macromolecules such as proteins nucleic

acids lipids and carbohydrates that's all they do so that's important thing to remember from these hydrolytic enzymes

is they're going to be responsible for doing what these all

break down macromolecules they break down macromolecules their respective

macromolecules as we already said okay that's one thing that i really want you to remember the second thing

you know when organelles are getting worn down maybe our mitochondria it's just it's had a rough day maybe the

cytoskeleton's starting to get all jacked up maybe our ribosomes have just they've pooped out and they're done

when these organelles have reached the end of their kind of let's say functional capacity we don't want to

keep them anymore we want to recycle them we want to break out with the old in with the new so what happens is these

lysosomes you'll actually take and package let's say that the ribosomes are done they're

tired they're pooped out i'm going to form a little vesicle around these ribosomes and then what i'm going to do

is i'm going to send it to the lysosome and what did i say that the ribosomes are made up of proteins and rna

so what do you think which enzymes are going to start breaking down this ribosome if you bring it to this

lysosome the proteases and the nucleases and it'll start breaking down the actual organelle what is that called autophagy

so another important thing that you have to remember is that this is one thing breaking down

macromolecules the second thing is it undergoes auto phagy

of organelles ba-boom last thing

let's say that a cell has actually been severely damaged you've really damaged this cell the

point of the cell is at living and surviving anymore is that it's it's not going to happen

you know what i'm going to do i'm going to just have these lysosomes bust open

and i'm going to have all of these enzymes proteases nucleases lipase glucosidases guess what they're going to

do they're going to break down all the macromolecule components of the cell what is that called that's called

autolysis so that's the next thing to remember is autolysis of

damaged cells okay so cells that even if they are damaged and you want to repair them

there's no point of even repairing them at that point it's time to just start all over these things will just bust

open and release their enzymes and start breaking down the cell this is the functions of the lysosomes

they're little angry little buggers aren't they all right next one pretty cool ones

these are actually kind of one of my favorite organelles and these are called peroxisomes

so peroxisomes these are also spherical kind of like little organelles

and they contain a lot of different enzymes but by far one of the most interesting enzymes that they contain

is there's two of them one is called catalase and the other one is called oxidase

they have other enzymes okay they have like other like metabolic enzymes we're going to title

them as that because it can be kind of confusing if you get into more detail than that but these are

the big enzymes so the first one i want you to remember is the catalases oxidases and then other metabolic

enzymes why am i kind of telling you all of these things

well the catalase in the oxidase is important for free radicals you know whenever a cell

normally obtains oxygen that oxygen can get sometimes converted into what's called a superoxide anion

then that superoxide anti can get converted into hydrogen peroxide and then that hydrogen peroxide can get

converted into what's called a hydroxyl radical these things right here from here to

here all of these molecules are free radicals very dangerous little suckers can bind onto proteins and nucleic acids

and cell membrane and just jack the cell up we don't want these things to accumulate

the particular one that loves to accumulate though in these peroxisomes because of what's called fatty acid

metabolism is hydrogen peroxide it really likes to accumulate in there so what happens is

these peroxisomes have lots of this catalase enzyme and what they do is they take this

hydrogen peroxide and use that catalase enzyme to convert this into

water and oxygen which is not that's not that dangerous right that's

what we want so that's one of the beautiful things be thankful for these suckers these little

peroxisomes they're not they're constantly breaking down this hydrogen peroxide which is a potential free

radical and making water and oxygen that's one thing you know it's important for fatty acid metabolism so they

contain little enzymes here particularly catalysts you know catalase not only is important for these free

radicals but it also can break down fatty acids the first step in fatty acid metabolism so it plays around what's

called fatty acid oxidation without going into too much detail there's actually two types alpha

and beta and really all this is is there's diff what's that called branch chain alpha breaks down what's called

branch chain fatty acids and then beta breaks down it's called very long chain fatty acids but either

way you're breaking down these fatty acids into what's called acetyl-coa molecules

then not only can it break down fatty acids but it can actually break down the fatty

acids into acetyl coa and then we can use those acetyl-coa molecules to make lipids

so we can actually make it can make lipids and there's a very particular type of

lipid and cholesterol and you know cholesterol is important

because this is also important for making different types of hormones steroid hormones and bile acids

but this is the one i want to focus on for a second the lipid that it makes is very

important within the white matter of the brain called plasmalogin

and this plasmalogin is a very particular type of lipid that is important for

the white matter so it's an important component of the myelin

within the white matter so you can have an idea that if there's an issue with the peroxisomes and they can't actually

synthesize plasmalogen what happens to the white matter there may be a decrease in white matter production and that may

lead to some injuries to the actual nervous system the last thing i want you to remember

is that there's also a teensy bit of alcohol metabolism so it also can break

down ethanol there's a tiny little enzyme that catalase enzyme again coming into

play not only with the fatty acids but also with the ethanol metabolism it can also break down ethanol so these

are some of the functions of the peroxisomes very very important type of little organelle now that we've covered

that one let's go into the mitochondria all right ninja so the next organelle that we're going to talk about here is

our mitochondria now the mitochondria is a very cool enzyme i'm sorry a very cool organelle

and this thing is commonly just broken down into like the simplest way of explaining it

everybody always knows this it's the powerhouse of the cell it's the the site of atp synthesis yes that is true but

we're going to explain about how it actually does that atp synthesis but before we do that again let's kind of

highlight some of the components of this mitochondria if you look at the mitochondria of an

outer membrane so this is the outer membrane and it's important to remember that the outer membrane is a smooth

membrane and also it has a very high

permeability there's a lot of transport proteins on the outer membrane if you look here you have this little

folded membrane here on the inside that is called the inner membrane

and usually on most cells we call this inner membrane the folding chris stay we call it the chris day of the inner

membrane now this inner membrane has less

permeability it's less permeable to the transport of different types of molecules going in and out of it okay so

that's the basics inside of the mitochondria you have this structure in here called the

mitochondrial matrix and this is where a lot of the metabolic reactions are occurring and it's also

where the mitochondrial dna is found all right so we have an idea of the structure of the mitochondria the next

thing is the function so it's obviously the site of

atp synthesis but if we were to just take it just a little step further

when we make atp we make it in two primary ways one is called oxidative phosphorylation the other one is called

substrate phosphorylation the mitochondria has little proteins on its inner membrane

that are very important and then a component of what's called the electron transport chain

so atp synthesis on the mitochondria in the mitochondria occurs via the electron transport chain

and this type of atp synthesis is called oxidative phosphorylation

okay and that's carried out by this electron transport chain

the other thing that's important with the mitochondria is that there's a lot of

metabolic reactions that occur here a lot of metabolic reactions what are some of these metabolic

reactions that occur within the mitochondria well some of them

as we know the krebs cycle that's an easy one right so the krebs cycle occurs here where you have a lot of different

intermediates that are involved whenever acetyl-coa gets converted into the entire complete structure right where

you have the acetyl-coa and then the isocitrate citrate alpha-ketoglutarate all that

stuff there that's a part of this metabolic reaction the other one

is you have heme synthesis so you're making the heme component of different types of uh

chrome different types of pigment molecules that are part of the electron transport

chain as well as synthesis of heme for hemoglobin or myoglobin the other one is the urea cycle occurs

here so the urea cycle is another big one where you're taking different types of molecules like

ammonia and turning it into urea the other one is called gluconeogenesis where you're taking

things like amino acids and glycerol and odd chain fatty acids and converting it into

glucose a new glucose molecule and the last thing that can occur here is what's called

ketogenesis where you're making ketone bodies from acetyl coa

so these are some of the metabolic pathways that occur within the mitochondria one other thing to remember

is i already told you about this but in the mitochondria it has its own little dna

so we'll put this up here this is called mitochondrial dna and this actually comes from the mother

okay so this is actually going to be dna that comes from the mother and this dna can actually make tiny little proteins

that can be involved in some of these metabolic reactions on its own all right so the next structure here is going to

be our ribosomes this is the next organelle now ribosomes we have already kind of alluded to these already so

we're going to have a pretty quick run through these but obviously we know that these ribosomes let's kind of talk a

little bit about their structure there's two components of the ribosome so you have this large ribosomal subunit so

this is the large subunit and usually they always like to say this

in eukaryotic cells this is your 60s ribosomes s means vedburg unit

but again large subunit and then the other one is called your small ribosomal

subunit and in eukaryotic cells this is a 40s or 40s vedburg unit of the ribosome again

kind of a very non-essential thing to remember but again big thing to remember is that there's two units a small

subunit and a large subunit the next thing that we have to remember ribosomes are made up of what two things

we already talked about this rrna and proteins

so that's the next thing the next thing is that ribosomes can be found in two places we already know one

it could be found on the rough endoplasmic reticulum whenever ribosomes are bound to the rough

endoplasmic reticulum we call these i know it's super obvious but it's called membrane

bound ribosomes okay so membrane-bound ribosomes but if these are just kind of

in the cytosol freely circulating then they are called cytosolic ribosomes or free ribosomes

the reason why we should understand the difference between these two is that if you guys remember

the ribosomes that were on the actual rough endoplasmic reticulum what happened what do ribosomes do i guess

that's the big question to ask let's actually write that down first what do ribosomes do

they take mrna and another structure called trna and make proteins so they're basically a

site of protein synthesis right and we also give this a

particular name called translation so whenever you're taking things like

mrna and making proteins well what happens is if you have

ribosomes that are bound to the rough er what are those proteins going to become remember what we said

those will become proteins that'll be a part of lysosomes those would be proteins that'll become a part of the

membrane like integral or peripheral proteins or they'll be proteins that we're going to excrete out of the cell

cytosolic ribosomes those are just going to be making little enzymes different types of proteins inside the

cell that will not leave the cell so that is important so these are going to be making cytosolic proteins

and i know that sounds obviously kind of pretty pretty straightforward but again it's something worth mentioning these

are making cytosolic proteins like different types of enzymes that are involved in a lot of your metabolic

pathways that occur in the cytosol okay so that's important so that gives us the importance of ribosomes what they uh

what their structure is and what they do now let's finish off with the cytoskeleton all right ninja so now we

got to talk about the cytoskeleton now obviously when we talk about the cytoskeleton the cytoskeleton we're only

showing in this kind of one point here but if you really were to show the way the cytoskeleton looks it would it would

make this board look disastrous because there would just be lines and fibers all over the entire cell

and that's an important thing to remember that even though we're showing this in kind of like a static zoomed in

view of these cytoskeletal elements remember they are scattered all around the cell that's an important thing to

remember okay when we talk about the cytoskeleton

there are three different structures of the cytoskeleton the first one that i want us to talk

about is called your micro filaments your microfilaments and sometimes to be honest with you we

just refer to this as actin okay and i know you guys have heard of actin if you guys have watched our

videos before you've heard this term actin it's one of the proteins that are commonly used in

muscle contraction right so that's an important thing to remember but when you look at actin there's these

little monomers of actin and they all come together and make this long polymer of actin and you get

multiple strands of it big thing i want you to remember with this actin structure

first thing when we talk about function you know when you have a muscle cell there's another protein that actin binds

with to cause contraction and relaxation what is that protein myosin so whenever you have actin

and myosin particularly in a contractile type of cell what can this do this can lead to muscle contraction and

relaxation so this is going to be a protein that can be involved in muscle contraction

that is a very important thing to remember so one thing i want you to remember with

the microfilaments are actin is that if it's associated with myosin it can be involved in contraction

the second thing you know in a cell if we were to have like a for example there's a process

called cytokinesis when a cell is undergoing mitosis you if you imagine here let's say that

here i had to a cell that was going to become two cells so here we had one cell that's becoming

two cells right around the central portion here you form this little constriction ring

right this little constriction ring around this point here these actin filaments form that

constriction ring and eventually squeeze it to the point where guess what happens you butt off from one cell

to daughter cells so it's important for the cytokinesis part of mitosis so cytokinesis

of mitosis so it forms a little constriction ring

around that which helps to split the cells apart the other thing it's important for

you know white blood cells if you take a white blood cell let's imagine here i have a white blood

cell and i want to move a white blood cell from the blood

i mean from the blood and have it leave and go out into the tissues well here's a vessel and you know the vessels lined

with what's called endothelial cells right well what happens is that this actual

white blood cell wants to be able to squeeze through those actual capillaries what is that called

diabetes in order for it to do that it needs to be able to change the shape

of the cell what do we say cytoskeletal elements do they help to control cell shape structure all that good stuff so

what happens is the actins polymerize in such a way that it allows for this cell to kind of

create a particular shape so all the actin molecules will come at this point and create like this little shape where

the white blood cell can squeeze out of the cell so what is that called

diapedesis diapedesis of

white blood cells and let's take this one more step let's say you have a white blood cell okay

and here's a little pathogen out here here's a little pathogen and i want to take this pathogen in

in order for me to do that i need to create these little like things called pseudopods

and what happens is i create these like little arms or little extensions that come out here to

surround that pathogen the actin molecules need to come in and

help to create these little arms that'll basically wrap around the pathogen and bring it in what is that called

phagocytosis so it's also involved in phagocytosis of white blood cells babushka we did it

all right next one the next one is the intermediate

filaments the inter mediate filaments

the intermediate filaments are a very interesting type of structure and one of the things that we need to

know about these intermediate filaments is that they are primarily very tough high tensile not very much movement they

don't give they don't have a lot of give to them so why that is important is let's say

that we take here a cell here is a another cell okay we have two cells and then you know

around the cell there's a lot of protein network out here what is this called all this

protein network that sits outside of the cell this is called your extracellular matrix it's made up of collagen and

elastin and a bunch of different types of proteins we know that right well what happens is we take this

protein here let's actually draw it in another color here let's use this blue here

this protein here let's say here we have one end of it it can connect to

from the cell can connect the cell to the extracellular matrix that's one thing it

can do so it can help to hold the cell and anchor it to the extracellular matrix

the other thing here is maybe i have another protein here another protein here in these cells

these can connect cell to cell

so they help to anchor and hold the cells to each other and then let's add another thing in here

you know these little organelles remember i told you that if you imagine the cytoskeleton

they're all over this cell imagine here i draw an organelle a mitochondria

or you know the nucleus whatever here's our nucleus

right these cytoskeletal elements are also going to be bound

to these organelles so it helps to anchor the actual cell to the extracellular mantra matrix anchor

cell to cell and anchor the organelles inside of the cell so they're not just kind of like [ __ ] floating around

everywhere right so that is the function of the intermediate filaments so three functions

is an anchor if you will and it anchors what things

one is cell to cell two is cell

to the extracellular matrix and three is sell to different organelles

we done did it okay so the last component here the last part is this microtubules these are very

very cool cytoskeletal elements okay and what i really want you to remember

about microtubules okay is they're made up of two different types of protein units so i drew these

in different colors a pink protein maybe that represents what's called alpha tubulin

and pretty straightforward right and then with my blue marker here another little dot here is called beta

tubulin these things come together and form these little filaments

and then like 13 filaments come together and eventually form this entire microtubular structure

why this is important is very very interesting so microtubules one of the really big function here

is that it provides what's called intra cellular transport

okay now it's a it seems odd but on these microtubules you have these little proteins imagine here you have like a

little protein here okay and these proteins there's two different

types of them there's what's called dynein and another one which is called

kinesin and these are called motor proteins and what these motor proteins can do is

they can bind on to organelles they can bind on to different vesicles which maybe have proteins or lipids or things

that you're moving towards the cell membrane are bringing in to the cell these are transporting them throughout

the cell to different places that they need to go to that is very important so again it's

acting as the the railway right or the railroad system by which you're transporting different

substances by having to use these motor proteins big thing to take away from this

this isn't there's no free lunch on this this requires atp to drive this process this is an atp

dependent process for this intracellular motor protein transport the second thing that's important for is

cell division you know whenever a cell is going through

the mitosis phase there is this phase where you have the chromosomes

like this right and they're all lined up okay

and metaphase well at that point here the centromere there's little proteins on the side

called the kinetochore what happens is these microtubules they click in to that kinetochore

and what happens is as they start to break down they depolymerize it separates these chromosomes into the two

separate sister chromatids so again big thing microtubules connect to the kinetochore where the centromere is the

center part of the chromosome and separate them into sister chromatids so that's the other important thing is cell

division particularly separating separates

the chromatids okay the third thing here is it is important for cellular extensions

cell extensions and what i mean by these extensions is

there's two big structures they form the base of these structures

and you form what's called the cilia which is a very important structure and you form what's called flagella

these are structures that again you have motor proteins like dyneins and things like that that are

incorporated into this these uh cellular extensions but what happens is these cilia and flagella they create a

beating like motion or twisting like motion and what that helps for is that if you