Understanding the Structure and Function of the Cell Nucleus

foreign what's up Ninja nerds in this video today we're going to be talking about

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with me without further Ado let's talk about the cell nucleus so the nucleus we're going to talk about is

the structure and the function so what I really want to do is I want to cover the components of the actual nuclear

structure and it's really kind of two things you see here we have a cell and then again

within the cell you have your intracellular fluid and then here you have your extracellular flu we already

talked about the cell membrane how it's separating those two right we went over the membrane lipids the membrane

proteins the cholesterol the glycocalic structure all that stuff well here I want you to think about this

structure here surrounding the inner side so this right here is your nucleus this whole thing right here is your

nucleus but there's a structure that's surrounding the inner components of the nucleus you see this this is called your

nuclear envelope and we'll go over all the different components of the nuclear envelope but

it's really really cool there's three components of it and we'll talk about that structure here

the next one here is inside of the nucleus there is the nuclear content and we'll go over in great detail what the

nuclear content is it's primarily made up of two things one is the nucleolus and one is the chromatin and we'll go

over that more detail later but let's actually take some time now we know the two structural components of

the nucleus is the nuclear envelope and then the next one is the nuclear content let's dive in each one nuclear envelope

if we were to take this nuclear envelope here this little son of a gun right here and zoom in on it in great detail this

is what we get this is our nuclear envelope and with the nuclear envelope you have this part here and this is

going to be the membrane and there's two components of this membrane and I'm not kidding it's very straightforward this

is the outer membrane oh man super complicated isn't it so first one is the outer

membrane and again this outer membrane is made up of phospholipids it's made up of phospholipids so you're going to see

the phosphate groups you're going to see the fatty acid tails you may even have some cholesterol within that

the next thing here is you're going to have the inner membrane this is the inner membrane and this is going to be

another really important component as well and as you see here the inner membrane contains again this

phospholipid bilayer as well so here's your phosphate groups here's the fatty acid tails and there's another important

component here which is called your lamina so again outer membrane is made up of a phospho

lipid layer and then this one contains a phospho

lipid layer and a lamina

layer which is made up of these proteins called lamins very very important proteins okay

and then the last thing is you have these like orange proteins which are kind of plugged in and span their

integral proteins are transmembrane proteins that span the entire nuclear envelope these are called nuclear pores

these are called nuclear pores so again let's go ahead and quickly recap up to this point what are we covered nuclear

envelope consists of outer membrane which is a phospholipid layer inner membrane which has another

phospholipolar but this Green Layer here is called the laminal layer made up of lamin proteins

and then lastly here we have the nuclear pores and the nuclear pores are going to be the proteins that span the entire

nuclear envelope nuclear content so now we have the nuclear envelope which is the outer membrane inner membrane

nuclear pore inside is what all the juiciness right in this part here this red structure here this is called the

nucleolus so it's called the nucleolus all right so the nucleolus that's this component here and then

surrounding kind of all these like like squiggly lines around the edge of it is called the chromatin

and we will talk next about all of these different things so now what we've done is is we've completely covered

everything with the structure of the nucleus we've covered the nuclear envelope talking about outer inner and

nuclear pore we then talked about nuclear content which is the nucleolus and the chromatin

all cells have three things in common no matter what type of cell they are all cells have a cell membrane which

separates the inside of the cell from its environment cytoplasm which is a jelly-like fluid

and DNA which is the cell's genetic material there are two broad categories of cells

the first category is eukaryotic cells they have organelles which include the nucleus and other special parts

periodic cells are more advanced complex cells such as those found in plants and animals

the second category is prokaryotic cells they don't have a nucleus or membrane enclosed organelles they do have genetic

material but it's not contained within a nucleus prokaryotic cells are always one cell or unicellular organisms such as

bacteria so what are organelles organelle means little organ

organelles are the specialized parts of a cell that have unique jobs to perform let's start with the nucleus the control

center of the cell the nucleus contains DNA or genetic material

DNA dictates what the cell is going to do and how it's going to do it chromatin is the Tangled spread out form

of DNA found inside the nuclear membrane when a cell is ready to divide DNA condenses into structures known as

chromosomes the nucleus also contains a nucleolus which is a structure where ribosomes are

made now let's dig into a little bit more detail on the functions of the nuclear

envelope and then functions of the nuclear content all right my friend so now we're going to talk about the

functions of the actual nuclear envelope okay so when we talk about this we're going to go through each kind of step in

a little bit more detail so we know that it's made up of the outer membrane the inner membrane and we know it's also

made above the again nuclear pores is there some specific functions to that yes so outer membrane is actually really

cool because one of the cool things is as you can see here it's contiguous with the endoplasmic reticulum very specific

one though is it's very continuous with one of the structures called the rough endoplasmic reticulum and I love this

because it makes so much sense why it's continuous so here is our our chromatin what you'll learn later is that

chromatin is basically DNA okay and DNA will undergo this process called

transcription well you'll take DNA and convert it into mRNA so then we'll make this into what's called

mRNA this is a process called transcription mRNA loves to bind to what the ribosomes

so we call the structure of the rough endoplasmic reticulum because this connect kind of like these continuous

tubules that are continuous with the nuclear envelope particularly the outer membrane

and what it has on it is it has ribosomes and what happens is this ribosomes when

they get red by the uh by the when mRNA gets read by the ribosomes what it does is is it pushes into the rough

endoplasmic reticulum a protein so it pushes into the rough endoplasmic reticulum

a protein Isn't that cool and then what happens is while it's in the rough endoplasmic reticulum it undergoes some

specific modifications and then when it's done being modified in the rough endoplasmic reticulum it takes and says

okay I'm done modifying you let me go ahead and Bud a piece of you off into this vesicle here

and then what I'm going to do is is I'm going to break you off and then send you somewhere else to get further modified

and that's one of the really cool concepts of the outer membrane so what I want you to remember is the outer

membrane of the nuclear envelope is contiguous with the rough endoplasmic reticulum and why does it have to be in

such close proximity because the DNA in the nucleus will get transcribed into mRNA mRNA will get translated on

ribosomes on the rough ER which is very contiguous with the what outer membrane and then get utilized to make proteins

so protein synthesis get packaged and then sent to another structure called the Golgi which we'll talk about later

that's one really really cool concept of the outer membrane the second thing is the inner membrane

what is the inner membrane good for and don't say absolutely nothing all right the inner membrane is really really cool

so here we have the outer membrane which was contiguous with the rough endoplasmic reticulum which is an

endoplasmic reticulum studded with ribosomes DNA mRNA mRNA to the ribosomes gets translated into proteins pushed

into the rough ER and then modified and then sent to the Golgi the inner membrane a little bit different

so one of the big things the inner membrane has this protein here called lamins all right so it's called the

lamina but lamina is basically made up of lamin proteins

and these lamin proteins have many many different functions what are some of them they're involved in taking this

here this is DNA right DNA is basically going to be right here I'm just kind of

zooming in on it when DNA undergoes a very specific process where it makes more DNA

what is that called DNA replication this is important because in order for

us to replicate DNA it allows for us to take one cell and make what two perfectly identical cells via

mitosis so it's involved in the cell cycle in that particular way it also and then again lamins is

basically the thing that's helping and assisting in this particular process so let's actually draw a green arrow our

green plus signs to recognize that the lamin proteins are regulating are completely involved in this process

they're also involved in these two other processes which is what taking DNA and converting it into RNA

you know what this is called This is called transcription this is called transcription and there's

so many different types of RNA there is what mRNA which is the most important one which will get translated by

ribosomes there's TRNA which is important in protein synthesis there's our RNA which is also important in the

ribosomal formation so all of this is kind of helped with lamin proteins which are on the inner membrane and the last

thing is they organize the DNA

and condense the DNA and we'll talk about this later so you see how all of this kind of DNA here is kind of

condensed down near the Edge by the lamins the lamins help with that process they organize and then Compact and

condense the DNA as well so these are the three particular functions of the inner membrane with

most specifically involving the lamin proteins they're involved in DNA replication DNA transcription and

organization of the DNA inside of the nucleus let's now come down to the last

component of the nuclear envelope which is the nuclear pores and we've already kind of indirectly covered what they do

and it's really really cool so the nuclear pores are great because inside of the nuclear envelope is the nuclear

content the chromatin which is DNA and proteins and the nucleolus in order to make DNA what do you need

you need ions you need nucleotides you may need some proteins right so if I want to transport things into

the nucleus such as ions or such as amino acids or such as nucleotides

I have to use these nuclear pores to import these particular small molecules in and so these nuclear pores can allow

for import so maybe there's one example of importing specific types of molecules passively this would be a passive

example they don't require any type of ATP to perform this so there's no ATP required

but let's say that I want to move out large molecules such as

RNA right RNA in order for me to get this big molecule RNA out I may need to

utilize ATP so that's an active transport and this may be involved in export

exporting the material out of the nucleus and so if I move this RNA out let's say

that this is specific RNA is mRNA and I give you T RNA you know what these generally do these two go and combine

with what's called ribosomes ribosomes you know ribosomes these are

very very special chakras that we already talked about that are present where on the rough endoplasmic reticulum

or they can be free ribosomes but generally what happens is the MRNA will interact here and then the

TRNA will interact here and this will help us to synthesize proteins

so this will help us to synthesize proteins and some of these proteins maybe need to

be sent back in to the nucleus very very large proteins and so let's say that some of these proteins that I basically

have synthesized I want to send back into the nucleus well then in order for me to be able to

get these proteins back into the nucleus because maybe it's involved in some type of particular process I may need to

import them again but if they're really really large so if I have to import large

molecules right import small molecules it could be passive importing large molecules may require ATP to do

this so it's active one of the cool reasons why this is important is because you know inside of

the actual nucleus there's something called the nucleolus there's this structure here called the

nucleolus and we'll talk about this in just a little bit but the nucleolus is really really important because what it

contains is it contains something called rrna and it contains something called ribo

zomal subunits and I think that's super cool because we

actually synthesize proteins like ribosomal subunits send them back into the nucleus

and then what happens is this actual DNA will make RNA guess what's the other RNA that it makes R RNA and if we combine

that with the ribosomal subunits this will then kind of go into this area

here called the nucleolus and then it'll help to combine it and

make true ribosomes and then from there we'll send out these large proteins out of the nucleus out into the cytosol to

bind onto the rough ER so that it can perform more of the actual translation process so it's a

really really cool concept and again we'll recap this in a little bit but the basic component of the nuclear pores is

allow for the export of things from the nucleus out into the cytosol or to allow for things to come from the

cytosol into the nucleus big thing to take away from this is that if it's large molecules it requires ATP to

import them or export them that's an active process and if it's small molecules like ions or small amino acids

or small proteins or nucleotides that are needed and they're being imported then that is actually going to require

no ATP and it's a passive process okay at this point we have covered now the functions of the nuclear envelope that

being the outer inner membrane and the nuclear pores let's now move on to the functions of the nuclear content in

other words going over the nucleolus a little bit more and then going over the chromatin all right my friend so now

we're going to talk about the functions of the nuclear content so first thing I want to talk about is again when we talk

about nuclear content we said that it's made up of Chromatin and the nucleolus just like when we said nuclear envelope

was outer membrane intermembrane nuclear pores outer membrane continuous with the rough ER really involved in that kind of

process where DNA in the nucleus gets converted into mRNA combines the ribosomes on the rough ER and then helps

to make proteins inner membrane has lamin proteins which are involved in helping the process of DNA replication

DNA transcription and organizing the DNA and the nuclear pores allow for things that are molecules or such to move in

and out of the nucleus if it's large charge molecules big proteins big nucleic acids those require ATP to be

imported are exported if it's small ions amino acids small proteins and nucleotides those can be imported or

exported without ATP that's a passive process okay next thing is chromatin chromatin is

really just made up of two particular things so if we were to actually take this chromatin inside of the nucleus

it's actually going to be made up of one thing which is called histone proteins so good old histone proteins and the big

thing I want you to know about histone proteins is that they are positively charged and they're technically is eight

of the son of a guns eight of these different types of histone proteins with the histone proteins because

they're positively charged they're going to love to interact with things that are somewhat negatively charged and what do

you think is negatively charged my friends DNA so DNA is the other component here of Chromatin and DNA is

this double helix and it's actually negatively charged now that is the two components of what the

two components of Chromatin so one is DNA and the other one is histone proteins these make up most of it

there's other small percentages of things that are involved in chromatin but these are the two primary things

now when we talk about chromatin really what is the function of it so let's actually kind of dive into a little bit

let's talk about what are the functions of DNA and then really what are the job of the histone proteins because we know

that that's what makes a chromatin well DNA is really cool it's in the sense that I already know that I can

take DNA and use specific DNA polymerases to take this DNA and make more DNA so if I want to take DNA and

make more DNA which will help me in the process of replicating cells so taking one cell and then making two cells this

is an important process via DNA replication so that's one of the things that I could do with DNA is I could

replicate it which is important in making more cells what does this call when I take one cell and make two

identical cells this is the process called mitosis and this involves so many cells of our body

another concept is what if I take the DNA I take a piece of it a gene a very specific portion of it and I read it and

I transcribe it and make RNA specifically with these examples is mRNA but there is other rnas right I can make

mRNA I could also make another RNA called TRNA that's another example and I can make another RNA which is important

in ribosomes which is called rrna what is this process called when I take DNA and make RNA this is called

transcription why is transcription important transcription allows for you to take DNA

to make RNA RNA which is mRNA TRNA rrna are all involved in the process of reading mRNA

and making it into something called proteins and proteins are super super important because they're basically the

things that keep the cells going they play a role in structure they play a role in function and so very very

important process there so DNA is really cool in the sense that again you have the ability to replicate it or

transcribe it to make very specific many types of proteins that play a huge role in our cells being able to survive

the second thing is the histone proteins what do these things really do what do these little guys do

it's actually really cool one of the concepts here is let's say here we have some histone proteins right so it's an

octomer there's eight of these histone proteins kind of locked in here so the eight of these histone proteins that are

kind of locked in here what happens is DNA will wrap around

this actual histone proteins twice Isn't that cool so they'll wrap around

these histone proteins twice and what that does is

that allows for these kinds of DNA to get condensed so what we call this is really whenever these are kind of

wrapped around the the DNA is wrapped around the histone proteins we call this a nucleosome

nucleosome and what happens is you can take DNA you know how long DNA is it's two meters long imagine trying to fit

two meters of this stringy DNA into a nucleus you can't do that normally so the histone proteins will condense

the DNA look how it condenses the DNA to make it fit into the actual nucleus and that's

important because we need the DNA to condense in order for us to undergo the process of mitosis

because we don't want to have DNA being super loose and stringy because then it can actually cause lots of breaks and

damage to the DNA and that's why we know one of the best examples of condensing of the DNA is you know an example of

that is especially during mitosis we take the DNA and we compact it into this thing called a chromosome that's

all DNA in there but a chromosome is going to be one of the best examples of condensed DNA DNA wrapped around histone

proteins to really allow for it to fit properly in this nucleus and allow for it to easily be passed on from one cell

to the next without breaking strands or messing up the DNA really really cool another function of the histone proteins

is that they play a role in regulating they play a role in regulating they regulate

genes they play a role in gene expression so imagine here

there's a particular Gene right here that I want to read and I want to read it and I want to be able to make

something called mRNA from it that's really what I want to do I want to be able to read it and make mRNA so

transcription these histone proteins if you put certain things on them it will help them

to maybe tighten the DNA up or loosen the DNA so in other words if the DNA is tight can I actually read that kind of

Gene no if the DNA is looser will I be able to easily read that DNA and make an RNA yes

so here's the thing if I were to add on a methyl group so I'm going to add on what's called a

methyl group I'm going to do something called methylation methylation is the stop sign to the gene now look what I'm

going to do I'm going to condense this DNA to where I can't read the Gene and what this is

going to do is if I have this methyl group here so imagine here I add a methyl group

onto I'm just going to represent it with this dot here here's the methyl group on these histone proteins they will

condense the DNA so when they condense the DNA we actually say it's really hard to be able to provide transcription so

we will inhibit transcription you will not make any RNA

this type of DNA that's condensed we give it a very specific name right we call this heterochromatin

hetero chromatin I want you to remember highly condensed for heterochromatin highly

condensed and this is usually due to histone methylation

and the other situation if I add a acetyl group all right so usually this is kind of like this kind of structure

here I'm adding some type of carboxy group with like a methyl Groupon this is called

acetylation acetylation okay so I'm adding some type of carboxy group with like a methyl

group on it so here I'm going to draw this one like this I have these acetyl groups that are

added on to the histone proteins believe it or not it allows the histone proteins to then separate the DNA strands and

open up the genes so now this Gene is super opened up and since it's opened up now the actual

gene expression is in play so this will stimulate transcription and if I stimulate transcription guess what I'm

going to make from this DNA I'm going to make RNA and that is a really cool concept so it

doesn't condense the DNA instead what does it do it actually loosens

if you will the DNA you know we call that when you loosen the DNA it's called euchromatin so it's called U

chromatin and the way that I remember this one is expressed DNA so highly condensed DNA

Express DNA methylation shuts down transcription acetylation stimulates transcription acetally a methylation

will cause heterochromatin acetylation will cause U chromatin that's the big things that I want you guys to take away

from the chromatin function let's now talk about the next aspect here which is the nucleolus

so the nucleolus is the other component we talked about chromatin being the DNA and the histone proteins

and what they do DNA replication transcription talk about chromatin for the condensation we also taught I mean

histones for the condensation of DNA and then we also talked about it for gene expression the nucleolus is really cool

and what I want you to remember big big thing is nucleus is the site of rrna and ribosomal synthesis let me

explain okay from this DNA I'm going to make two RNA

molecules all right all right we'll say three we're going to make RNA okay

one of these is called R RNA and that goes over here to this nucleolocyte we'll also make TRNA

and mRNA and these will go out of the nucleus via the nuclear pores so here I'm going to have mRNA

and I'm going to have TRNA these will then go

and actually interact with a ribosome so here is going to be a ribosome and ribosomes can be free meaning they're

circulating in the cytosol or they can be bound to the rough endoplasmic reticulum

the MRNA will bind with the ribosome and the TRNA which we'll talk about later will carry a very specific type of

amino acid and from this they will synthesize what proteins so from this the whole goal is

to synthesize proteins with the MRNA and the TRNA okay so here's going to be our protein one thing I left out though

is that there's one more RNA so this is TRNA which carries the amino acid the codon I was at the anticodon mRNA

carries a specific code the codon but there's another molecule in the actual ribosome called

R RNA the nucleolus is actually what synthesizes the ribosomal subunit and the rrna

but how does it do that we're almost there so let's say we're making these proteins and just for the simplicity's

sake let's say that it's ribosomal proteins so let's actually make this red here's my ribosomal proteins or my

subunits okay where do these have to go well where the rrna is where's the rrna

it's in the nucleolus so what I'm going to do is I'm going to take these ribosomal subunits

and I'm going to bring it in and I'm going to combine the rrna and the what's this right here let's

actually just show them in Vivo here here's going to be our ribosomal subunits

I'm going to import them into the nucleus combine these two and when I combine these two I'm going to make

ribosomes and guess what I'm gonna do now that I have these two I'm going to

combine them together and I'm going to ship out of this nucleus via exporting via the nuclear pore I'm going to send

out my ribosomes here's my ribosomal subunit here's my ribosomal subunit and guess

what's kind of incorporated into the structure the r RNA

that's a really cool thing and then that will then kind of go and help you to make more of these which will help you

to make more proteins so really the nucleolus is really the site of taking R so if we

were to really take this nucleolus and zoom in on what happens here's my rrna here is my ribosomal

subunits the RNA comes from the DNA the ribosomal subunus comes from the protein that was

made via mRNA TRNA and a prior ribosome that had rrna and proteins in it and then from this I will synthesize more of

these so it just keeps manufacturing more of these ribosomes that will either

become free ribosomes or will become ribosomes that bind onto the

rough endoplasmic reticulum so the nucleolus is the site of ribosomal synthesis where rrna comes from the DNA

and the DNA makes mRNA and TRNA which helps to underminate translation making more ribosomal subunits sends it back

into the nucleus and combines with the RNA makes ribosomes and sends them out via export Isn't that cool I think it's

pretty cool but that is the concept there for the nucleus and that finishes the video on the nucleus structure and

function I hope it made sense I hope that you guys liked it as always until next time

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