Cell Biology | Cell Structure & Function

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

have these motor proteins which are

constantly utilizing atp to beat and

create this movement here cilia is good

in our respiratory tract because it

helps to clear out mucus it's also in

the fallopian tubes you know when you

have to move the o or the oocyte or the

ovum in this case if it's fertilized you

have to move it towards the uterus we

need those things and microtubules make

up the base of that cilia flagella in

order for the sperm to be able to move

towards the oocyte or the in this case

the secondary oocyte it needs to have

that type of motion and again

microtubules make up the base of the

flagella and utilize these dynein

proteins to create that whipping motion

so now we have an idea what these

microtubules do hi ninja so in this

video we covered the structure and

function of the cell it was a long one

but i hope it made sense and i truly

hope that you guys enjoyed it and i hope

you guys learned a lot if you guys

follow through this entire process of

how i study prepare draw and then go

through the lecture i hope that you guys

were able to come up with a similar

process and i hope it helped all right

nigerians as always we thank you love

you and until next time

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you