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Cell Nucleus Structure & Function — Transcript

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0:02foreign
0:06what's up Ninja nerds in this video
0:08today we're going to be talking about
0:09the cell nucleus before we get started
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0:27understand this topic and follow along
0:29with me without further Ado let's talk
0:31about the cell nucleus so
0:33the nucleus we're going to talk about is
0:34the structure and the function so what I
0:36really want to do is I want to cover the
0:37components of the actual nuclear
0:39structure and it's really kind of two
0:41things you see here we have a cell and
0:42then again
0:43within the cell you have your
0:45intracellular fluid and then here you
0:47have your extracellular flu we already
0:48talked about the cell membrane how it's
0:49separating those two right we went over
0:51the membrane lipids the membrane
0:52proteins the cholesterol the glycocalic
0:54structure all that stuff
0:56well here I want you to think about this
0:58structure here surrounding the inner
1:00side so this right here is your nucleus
1:02this whole thing right here is your
1:03nucleus but there's a structure that's
1:05surrounding the inner components of the
1:07nucleus you see this this is called your
1:10nuclear envelope
1:12and we'll go over all the different
1:14components of the nuclear envelope but
1:16it's really really cool there's three
1:18components of it and we'll talk about
1:20that structure here
1:21the next one here is inside of the
1:24nucleus there is the nuclear content and
1:26we'll go over in great detail what the
1:29nuclear content is it's primarily made
1:31up of two things one is the nucleolus
1:34and one is the chromatin and we'll go
1:35over that more detail later
1:37but let's actually take some time now we
1:39know the two structural components of
1:41the nucleus is the nuclear envelope and
1:43then the next one is the nuclear content
1:45let's dive in each one nuclear envelope
1:47if we were to take this nuclear envelope
1:49here this little son of a gun right here
1:52and zoom in on it in great detail this
1:54is what we get this is our nuclear
1:56envelope and with the nuclear envelope
1:58you have this part here and this is
2:01going to be the membrane and there's two
2:03components of this membrane and I'm not
2:05kidding it's very straightforward this
2:07is the outer membrane oh man super
2:10complicated isn't it so first one is the
2:13outer
2:14membrane and again this outer membrane
2:18is made up of phospholipids it's made up
2:21of phospholipids so you're going to see
2:23the phosphate groups you're going to see
2:25the fatty acid tails you may even have
2:26some cholesterol within that
2:28the next thing here is you're going to
2:30have the inner membrane this is the
2:32inner membrane and this is going to be
2:34another really important component as
2:37well and as you see here the inner
2:40membrane contains again this
2:42phospholipid bilayer as well so here's
2:45your phosphate groups here's the fatty
2:46acid tails and there's another important
2:48component here which is called your
2:50lamina so again outer membrane is made
2:53up of a phospho
2:55lipid
2:57layer
2:59and then this one contains a phospho
3:02lipid
3:04layer
3:05and a lamina
3:08layer which is made up of these proteins
3:10called lamins very very important
3:12proteins okay
3:14and then the last thing is you have
3:16these like orange proteins which are
3:18kind of plugged in and span their
3:20integral proteins are transmembrane
3:21proteins that span the entire nuclear
3:24envelope these are called nuclear pores
3:26these are called nuclear pores so again
3:30let's go ahead and quickly recap up to
3:32this point what are we covered nuclear
3:34envelope consists of outer membrane
3:36which is a phospholipid layer inner
3:39membrane which has another
3:40phospholipolar but this Green Layer here
3:42is called the laminal layer made up of
3:43lamin proteins
3:45and then lastly here we have the nuclear
3:48pores and the nuclear pores are going to
3:49be the proteins that span the entire
3:51nuclear envelope nuclear content so now
3:54we have the nuclear envelope which is
3:56the outer membrane inner membrane
3:58nuclear pore inside is what all the
4:02juiciness right in this part here this
4:05red structure here this is called the
4:07nucleolus so it's called the nucleolus
4:10all right so the nucleolus
4:13that's this component here and then
4:15surrounding kind of all these like like
4:17squiggly lines around the edge of it is
4:19called the chromatin
4:21and we will talk next about all of these
4:25different things so now what we've done
4:27is is we've completely covered
4:29everything with the structure of the
4:30nucleus we've covered the nuclear
4:32envelope talking about outer inner and
4:34nuclear pore we then talked about
4:36nuclear content which is the nucleolus
4:38and the chromatin
4:40all cells have three things in common no
4:43matter what type of cell they are
4:45all cells have a cell membrane which
4:48separates the inside of the cell from
4:50its environment
4:52cytoplasm which is a jelly-like fluid
4:55and DNA which is the cell's genetic
4:58material
5:01there are two broad categories of cells
5:05the first category is eukaryotic cells
5:09they have organelles which include the
5:12nucleus and other special parts
5:15periodic cells are more advanced complex
5:18cells such as those found in plants and
5:21animals
5:23the second category is prokaryotic cells
5:27they don't have a nucleus or membrane
5:30enclosed organelles they do have genetic
5:33material but it's not contained within a
5:35nucleus prokaryotic cells are always one
5:39cell or unicellular organisms such as
5:42bacteria
5:46so what are organelles
5:49organelle means little organ
5:53organelles are the specialized parts of
5:55a cell that have unique jobs to perform
5:59let's start with the nucleus the control
6:02center of the cell
6:05the nucleus contains DNA or genetic
6:08material
6:09DNA dictates what the cell is going to
6:12do and how it's going to do it
6:15chromatin is the Tangled spread out form
6:17of DNA found inside the nuclear membrane
6:22when a cell is ready to divide DNA
6:25condenses into structures known as
6:28chromosomes
6:33the nucleus also contains a nucleolus
6:37which is a structure where ribosomes are
6:39made
6:41now let's dig into a little bit more
6:43detail on the functions of the nuclear
6:45envelope and then functions of the
6:46nuclear content all right my friend so
6:48now we're going to talk about the
6:49functions of the actual nuclear envelope
6:51okay so when we talk about this we're
6:53going to go through each kind of step in
6:54a little bit more detail so we know that
6:56it's made up of the outer membrane the
6:57inner membrane and we know it's also
6:58made above the again nuclear pores is
7:01there some specific functions to that
7:02yes so outer membrane is actually really
7:05cool because one of the cool things is
7:06as you can see here it's contiguous with
7:09the endoplasmic reticulum very specific
7:12one though is it's very continuous with
7:14one of the structures called the rough
7:16endoplasmic reticulum and I love this
7:18because it makes so much sense why it's
7:21continuous so here is our our chromatin
7:23what you'll learn later is that
7:25chromatin is basically DNA
7:27okay and DNA will undergo this process
7:30called
7:32transcription well you'll take DNA and
7:35convert it into mRNA so then we'll make
7:38this into what's called
7:39mRNA this is a process called
7:41transcription
7:43mRNA loves to bind to what the ribosomes
7:49so we call the structure of the rough
7:50endoplasmic reticulum because this
7:52connect kind of like these continuous
7:54tubules that are continuous with the
7:56nuclear envelope particularly the outer
7:58membrane
7:59and what it has on it is it has
8:01ribosomes
8:02and what happens is this ribosomes when
8:06they get red by the uh by the when mRNA
8:09gets read by the ribosomes what it does
8:11is is it pushes into the rough
8:14endoplasmic reticulum a protein
8:17so it pushes into the rough endoplasmic
8:20reticulum
8:21a protein Isn't that cool and then what
8:23happens is while it's in the rough
8:25endoplasmic reticulum it undergoes some
8:27specific modifications and then when
8:30it's done being modified in the rough
8:32endoplasmic reticulum it takes and says
8:34okay I'm done modifying you let me go
8:37ahead and Bud a piece of you off into
8:40this vesicle here
8:41and then what I'm going to do is is I'm
8:43going to break you off and then send you
8:45somewhere else to get further modified
8:47and that's one of the really cool
8:49concepts of the outer membrane so what I
8:52want you to remember is the outer
8:53membrane of the nuclear envelope is
8:55contiguous with the rough endoplasmic
8:58reticulum and why does it have to be in
9:00such close proximity because the DNA in
9:02the nucleus will get transcribed into
9:05mRNA mRNA will get translated on
9:07ribosomes on the rough ER which is very
9:09contiguous with the what outer membrane
9:12and then get utilized to make proteins
9:14so protein synthesis get packaged and
9:16then sent to another structure called
9:17the Golgi which we'll talk about later
9:20that's one really really cool concept of
9:22the outer membrane
9:24the second thing is the inner membrane
9:25what is the inner membrane good for and
9:27don't say absolutely nothing all right
9:29the inner membrane is really really cool
9:30so here we have the outer membrane which
9:32was contiguous with the rough
9:33endoplasmic reticulum which is an
9:35endoplasmic reticulum studded with
9:36ribosomes DNA mRNA mRNA to the ribosomes
9:40gets translated into proteins pushed
9:42into the rough ER and then modified and
9:44then sent to the Golgi the inner
9:46membrane a little bit different
9:48so one of the big things the inner
9:49membrane has this protein here called
9:51lamins all right so it's called the
9:54lamina but lamina is basically made up
9:56of
9:57lamin proteins
10:00and these lamin proteins have many many
10:03different functions what are some of
10:05them they're involved in taking this
10:07here this is DNA
10:09right DNA is basically
10:11going to be right here I'm just kind of
10:12zooming in on it when DNA undergoes a
10:15very specific process where it makes
10:17more DNA
10:18what is that called
10:20DNA replication
10:22this is important because in order for
10:24us to replicate DNA it allows for us to
10:26take one cell and make what
10:29two perfectly identical cells via
10:31mitosis so it's involved in the cell
10:33cycle in that particular way
10:35it also and then again lamins is
10:37basically the thing that's helping and
10:39assisting in this particular process so
10:41let's actually draw a green arrow our
10:42green plus signs to recognize that the
10:45lamin proteins are regulating are
10:47completely involved in this process
10:49they're also involved in these two other
10:51processes which is what
10:53taking DNA and converting it into RNA
10:56you know what this is called This is
10:58called transcription
11:00this is called transcription and there's
11:02so many different types of RNA there is
11:05what mRNA which is the most important
11:07one which will get translated by
11:08ribosomes there's TRNA which is
11:11important in protein synthesis there's
11:13our RNA which is also important in the
11:15ribosomal formation so all of this is
11:18kind of helped with lamin proteins which
11:20are on the inner membrane and the last
11:22thing is
11:24they organize
11:27the DNA
11:29and condense the DNA and we'll talk
11:31about this later so you see how all of
11:34this kind of DNA here is kind of
11:36condensed down near the Edge by the
11:38lamins the lamins help with that process
11:40they organize and then Compact and
11:42condense the DNA as well
11:44so these are the three particular
11:45functions of the inner membrane with
11:47most specifically involving the lamin
11:50proteins they're involved in DNA
11:52replication DNA transcription and
11:54organization of the DNA inside of the
11:57nucleus
11:58let's now come down to the last
11:59component of the nuclear envelope which
12:01is the nuclear pores and we've already
12:02kind of indirectly covered what they do
12:04and it's really really cool so the
12:07nuclear pores are great because inside
12:09of the nuclear envelope is the nuclear
12:12content the chromatin which is DNA and
12:14proteins and the nucleolus
12:16in order to make DNA what do you need
12:19you need ions you need nucleotides you
12:21may need some proteins right
12:23so if I want to transport things into
12:27the nucleus such as ions
12:30or such as amino acids or such as
12:33nucleotides
12:36I have to use these nuclear pores to
12:39import these particular small molecules
12:42in and so these nuclear pores can allow
12:45for import so maybe there's one example
12:47of importing specific types of molecules
12:50passively this would be a passive
12:52example they don't require any type of
12:54ATP to perform this so there's no ATP
12:57required
12:58but
12:59let's say that I want to move out large
13:02molecules such as
13:04RNA
13:06right RNA in order for me to get this
13:09big molecule RNA out I may need to
13:12utilize ATP so that's an active
13:14transport and this may be involved in
13:16export
13:18exporting the material out of the
13:21nucleus
13:23and so if I move this RNA out let's say
13:25that this is specific RNA is mRNA and I
13:29give you T RNA you know what these
13:32generally do these two go and combine
13:35with what's called
13:36ribosomes
13:38ribosomes you know ribosomes these are
13:40very very special chakras that we
13:41already talked about that are present
13:43where on the rough endoplasmic reticulum
13:45or they can be free ribosomes
13:48but generally what happens is
13:50the MRNA will interact here and then the
13:53TRNA
13:54will interact here and this will help us
13:57to synthesize proteins
13:59so this will help us to synthesize
14:01proteins
14:02and some of these proteins maybe need to
14:04be sent back in to the nucleus very very
14:08large proteins and so let's say that
14:10some of these proteins that I basically
14:11have synthesized
14:13I want to send back into the nucleus
14:16well then in order for me to be able to
14:18get these proteins back into the nucleus
14:20because maybe it's involved in some type
14:21of particular process I may need to
14:23import them again but if they're really
14:26really large so if I have to import
14:30large
14:32molecules right import small
14:37molecules it could be passive importing
14:39large molecules may require ATP to do
14:42this so it's active
14:44one of the cool reasons why this is
14:45important is because you know inside of
14:47the actual nucleus there's something
14:48called the nucleolus
14:50there's this structure here called the
14:52nucleolus and we'll talk about this in
14:54just a little bit but the nucleolus is
14:56really really important because what it
14:58contains is it contains something called
15:00rrna
15:02and it contains something called ribo
15:05zomal
15:07subunits
15:10and I think that's super cool because we
15:13actually synthesize proteins like
15:15ribosomal subunits send them back into
15:17the nucleus
15:19and then what happens is this actual DNA
15:22will make RNA guess what's the other RNA
15:24that it makes R RNA and if we combine
15:28that with the
15:30ribosomal subunits
15:33this will then kind of go into this area
15:35here
15:36called the nucleolus
15:38and then it'll help to combine it and
15:40make true ribosomes and then from there
15:42we'll send out these large proteins out
15:45of the nucleus out into the cytosol to
15:47bind onto the
15:49rough ER so that it can perform more of
15:51the actual translation process so it's a
15:54really really cool concept and again
15:55we'll recap this in a little bit but the
15:57basic component of the nuclear pores is
15:59allow for the export of things from the
16:02nucleus out into the cytosol
16:05or to allow for things to come from the
16:07cytosol into the nucleus big thing to
16:10take away from this is that if it's
16:11large molecules it requires ATP to
16:15import them or export them that's an
16:17active process and if it's small
16:19molecules like ions or small amino acids
16:21or small proteins or nucleotides that
16:24are needed and they're being imported
16:26then that is actually going to require
16:27no ATP and it's a passive process okay
16:31at this point we have covered now the
16:33functions of the nuclear envelope that
16:36being the outer inner membrane and the
16:38nuclear pores let's now move on to the
16:39functions of the nuclear content in
16:41other words going over the nucleolus a
16:43little bit more and then going over the
16:45chromatin all right my friend so now
16:47we're going to talk about the functions
16:48of the nuclear content so first thing I
16:50want to talk about is again when we talk
16:51about nuclear content we said that it's
16:52made up of Chromatin and the nucleolus
16:55just like when we said nuclear envelope
16:56was outer membrane intermembrane nuclear
16:58pores outer membrane continuous with the
17:00rough ER really involved in that kind of
17:02process where DNA in the nucleus gets
17:04converted into mRNA combines the
17:06ribosomes on the rough ER and then helps
17:07to make proteins inner membrane has
17:09lamin proteins which are involved in
17:11helping the process of DNA replication
17:13DNA transcription and organizing the DNA
17:16and the nuclear pores allow for things
17:18that are molecules or such to move in
17:22and out of the nucleus if it's large
17:24charge molecules big proteins big
17:27nucleic acids those require ATP to be
17:30imported are exported if it's small ions
17:33amino acids small proteins and
17:35nucleotides those can be imported or
17:37exported without ATP that's a passive
17:39process okay
17:41next thing is chromatin chromatin is
17:43really just made up of two particular
17:44things so if we were to actually take
17:46this chromatin inside of the nucleus
17:48it's actually going to be made up of one
17:50thing which is called histone proteins
17:52so good old histone proteins and the big
17:55thing I want you to know about histone
17:57proteins is that they are positively
17:58charged and they're technically is eight
18:01of the son of a guns eight of these
18:04different types of histone proteins
18:06with the histone proteins because
18:08they're positively charged they're going
18:10to love to interact with things that are
18:12somewhat negatively charged and what do
18:15you think is negatively charged my
18:16friends DNA so DNA is the other
18:19component here of Chromatin and DNA is
18:22this double helix and it's actually
18:24negatively charged now
18:27that is the two components of what the
18:30two components of Chromatin so one is
18:32DNA and the other one is histone
18:35proteins these make up most of it
18:38there's other small percentages of
18:39things that are involved in chromatin
18:41but these are the two primary things
18:43now when we talk about chromatin really
18:46what is the function of it so let's
18:47actually kind of dive into a little bit
18:49let's talk about what are the functions
18:51of DNA and then really what are the job
18:53of the histone proteins because we know
18:54that that's what makes a chromatin
18:56well DNA is really cool it's in the
18:58sense that I already know that I can
18:59take DNA and use specific DNA
19:01polymerases to take this DNA and make
19:05more DNA so if I want to take DNA and
19:08make more DNA which will help me in the
19:11process of replicating cells so taking
19:14one cell and then making two cells this
19:16is an important process via DNA
19:19replication so that's one of the things
19:22that I could do with DNA is I could
19:23replicate it which is important in
19:25making more cells what does this call
19:28when I take one cell and make two
19:29identical cells this is the process
19:31called mitosis and this involves so many
19:35cells of our body
19:37another concept is what if I take the
19:39DNA I take a piece of it a gene a very
19:42specific portion of it and I read it and
19:45I transcribe it and make RNA
19:47specifically with these examples is mRNA
19:50but there is other rnas right I can make
19:53mRNA I could also make another RNA
19:56called TRNA that's another example and I
20:00can make another RNA which is important
20:02in ribosomes which is called
20:04rrna what is this process called when I
20:06take DNA and make RNA this is called
20:10transcription why is transcription
20:12important
20:14transcription allows for you to take DNA
20:17to make RNA
20:19RNA which is mRNA TRNA rrna are all
20:24involved in the process of reading mRNA
20:27and making it into something called
20:29proteins and proteins are super super
20:33important because they're basically the
20:35things that keep the cells going they
20:37play a role in structure they play a
20:39role in function and so very very
20:41important process there so DNA is really
20:44cool in the sense that again you have
20:46the ability to replicate it or
20:48transcribe it to make very specific many
20:50types of proteins that play a huge role
20:53in our cells being able to survive
20:56the second thing is the histone proteins
20:58what do these things really do what do
20:59these little guys do
21:00it's actually really cool one of the
21:02concepts here is let's say here we have
21:04some histone proteins right so it's an
21:05octomer there's eight of these histone
21:07proteins kind of locked in here so the
21:09eight of these histone proteins that are
21:10kind of locked in here what happens is
21:12DNA will wrap
21:15around
21:17this actual
21:19histone proteins twice
21:22Isn't that cool so they'll wrap around
21:24these histone proteins
21:26twice
21:27and what that does is
21:30that allows for these kinds of DNA to
21:33get condensed so what we call this is
21:35really whenever these are kind of
21:37wrapped around the the DNA is wrapped
21:39around the histone proteins we call this
21:41a nucleosome
21:43nucleosome and what happens is you can
21:45take DNA you know how long DNA is it's
21:47two meters long imagine trying to fit
21:50two meters of this stringy DNA into a
21:52nucleus you can't do that normally so
21:55the histone proteins will condense
21:58the DNA
21:59look how it condenses the DNA to make it
22:02fit into the actual nucleus and that's
22:05important because we need the DNA to
22:06condense in order for us to undergo the
22:08process of mitosis
22:11because we don't want to have DNA being
22:12super loose and stringy because then it
22:14can actually cause lots of breaks and
22:16damage to the DNA and that's why we know
22:17one of the best examples of condensing
22:19of the DNA is you know an example of
22:21that is especially during mitosis
22:24we take the DNA and we compact it into
22:27this thing called a chromosome that's
22:30all DNA in there but a chromosome is
22:33going to be one of the best examples of
22:35condensed DNA DNA wrapped around histone
22:39proteins to really allow for it to fit
22:41properly in this nucleus and allow for
22:43it to easily be passed on from one cell
22:45to the next without breaking strands or
22:47messing up the DNA really really cool
22:50another function of the histone proteins
22:52is that they play a role in regulating
22:55they play a role in regulating
22:58they regulate
23:00genes
23:02they play a role in gene expression so
23:04imagine here
23:05there's a particular Gene right here
23:07that I want to read and I want to read
23:11it and I want to be able to make
23:12something called mRNA from it that's
23:14really what I want to do I want to be
23:15able to read it and make mRNA so
23:17transcription
23:18these histone proteins if you put
23:21certain things on them it will help them
23:24to maybe tighten the DNA up or loosen
23:26the DNA so in other words if the DNA is
23:28tight can I actually read that kind of
23:31Gene no if the DNA is looser will I be
23:33able to easily read that DNA and make an
23:35RNA yes
23:36so here's the thing
23:38if I were to add on a methyl group so
23:41I'm going to add on what's called a
23:42methyl group I'm going to do something
23:44called methylation methylation is the
23:47stop sign to the gene now look what I'm
23:49going to do
23:50I'm going to condense this DNA to where
23:53I can't read the Gene and what this is
23:55going to do is if I have this methyl
23:57group here so imagine here I add a
23:59methyl group
24:01onto I'm just going to represent it with
24:03this dot here here's the methyl group on
24:05these histone proteins they will
24:06condense the DNA so when they condense
24:09the DNA we actually say it's really hard
24:12to be able to provide transcription so
24:15we will inhibit
24:17transcription you will not make
24:20any RNA
24:22this type of DNA that's condensed we
24:24give it a very specific name right we
24:26call this heterochromatin
24:28hetero
24:30chromatin I want you to remember highly
24:32condensed for heterochromatin highly
24:34condensed
24:35and this is usually due to
24:38histone methylation
24:41and the other situation if I add a
24:43acetyl group all right so usually this
24:45is kind of like this kind of structure
24:46here I'm adding some type of carboxy
24:48group with like a methyl Groupon this is
24:50called
24:51acetylation
24:54acetylation okay so I'm adding some type
24:57of carboxy group with like a methyl
24:58group on it so here I'm going to draw
25:00this one like this
25:02I have these acetyl groups that are
25:04added on to the histone proteins believe
25:07it or not it allows the histone proteins
25:09to then separate the DNA strands and
25:12open up the genes
25:14so now this Gene is super opened up
25:18and since it's opened up now the actual
25:21gene expression is in play so this will
25:24stimulate transcription and if I
25:26stimulate transcription guess what I'm
25:28going to make from this DNA I'm going to
25:30make RNA
25:32and that is a really cool concept so it
25:34doesn't condense the DNA instead what
25:36does it do
25:37it actually loosens
25:40if you will the DNA you know we call
25:43that when you loosen the DNA
25:45it's called euchromatin so it's called U
25:50chromatin and the way that I remember
25:52this one
25:53is expressed DNA so highly condensed DNA
25:58Express DNA methylation shuts down
26:01transcription acetylation stimulates
26:04transcription acetally a methylation
26:06will cause heterochromatin acetylation
26:09will cause U chromatin that's the big
26:11things that I want you guys to take away
26:12from the chromatin function
26:15let's now talk about the next aspect
26:18here which is the nucleolus
26:19so the nucleolus is the other component
26:22we talked about chromatin being the DNA
26:23and the histone proteins
26:25and what they do DNA replication
26:27transcription talk about chromatin for
26:29the condensation we also taught I mean
26:31histones for the condensation of DNA and
26:33then we also talked about it for gene
26:34expression the nucleolus is really cool
26:36and what I want you to remember big big
26:38thing is nucleus is the site of
26:40rrna and ribosomal synthesis let me
26:44explain
26:45okay
26:46from this DNA I'm going to make two RNA
26:49molecules
26:51all right all right we'll say three
26:53we're going to make RNA okay
26:56one of these is called R RNA and that
26:59goes over here to this nucleolocyte
27:01we'll also make TRNA
27:04and mRNA and these will go out of the
27:09nucleus via the nuclear pores
27:11so here I'm going to have mRNA
27:15and I'm going to have
27:16TRNA
27:19these will then go
27:21and actually interact with a ribosome so
27:25here is going to be a ribosome and
27:26ribosomes can be free meaning they're
27:29circulating in the cytosol or they can
27:31be bound to the rough endoplasmic
27:32reticulum
27:33the MRNA will bind with the ribosome
27:36and the TRNA which we'll talk about
27:39later will carry a very specific type of
27:41amino acid and from this they will
27:44synthesize what
27:46proteins so from this the whole goal is
27:49to synthesize proteins with the MRNA and
27:52the TRNA okay so here's going to be our
27:55protein one thing I left out though
27:58is that there's one more RNA so this is
28:00TRNA which carries the amino acid the
28:03codon I was at the anticodon mRNA
28:06carries a specific code the codon but
28:08there's another molecule in the actual
28:10ribosome called
28:12R RNA the nucleolus is actually what
28:15synthesizes the ribosomal subunit and
28:18the rrna
28:20but how does it do that we're almost
28:22there so let's say we're making these
28:23proteins and just for the simplicity's
28:25sake let's say that it's ribosomal
28:27proteins so let's actually make this red
28:30here's my ribosomal proteins or my
28:33subunits okay
28:35where do these have to go well where the
28:37rrna is where's the rrna
28:40it's in the nucleolus
28:42so what I'm going to do is I'm going to
28:43take these ribosomal subunits
28:50and I'm going to bring it in
28:51and I'm going to combine the rrna
28:55and the what's this right here let's
28:57actually just show them in Vivo here
29:00here's going to be our
29:02ribosomal subunits
29:05I'm going to import them into the
29:07nucleus combine these two and when I
29:10combine these two I'm going to make
29:11ribosomes
29:12and guess what I'm gonna do
29:14now that I have these two I'm going to
29:16combine them together and I'm going to
29:18ship out of this nucleus via exporting
29:21via the nuclear pore I'm going to send
29:23out
29:24my ribosomes here's my ribosomal subunit
29:27here's my ribosomal subunit and guess
29:29what's kind of incorporated into the
29:31structure
29:32the r RNA
29:34that's a really cool thing and then that
29:37will then kind of go and help you to
29:38make more of these which will help you
29:40to make more proteins so really the
29:42nucleolus
29:43is really the site of taking R so if we
29:46were to really take this nucleolus and
29:47zoom in on what happens here's my rrna
29:50here is my ribosomal
29:55subunits
29:58the RNA comes from the DNA the ribosomal
30:02subunus comes from the protein that was
30:03made via mRNA TRNA and a prior ribosome
30:07that had rrna and proteins in it and
30:10then from this I will synthesize more of
30:12these
30:13so it just keeps manufacturing more
30:17of these ribosomes that will either
30:20become free ribosomes
30:22or
30:24will become ribosomes that bind onto the
30:26rough endoplasmic reticulum so the
30:29nucleolus is the site of ribosomal
30:31synthesis where rrna comes from the DNA
30:35and the DNA makes mRNA and TRNA which
30:37helps to underminate translation making
30:39more ribosomal subunits sends it back
30:41into the nucleus and combines with the
30:43RNA makes ribosomes and sends them out
30:45via export Isn't that cool I think it's
30:48pretty cool but that is the concept
30:50there for the nucleus and that finishes
30:51the video on the nucleus structure and
30:53function I hope it made sense I hope
30:54that you guys liked it as always until
30:56next time
31:01[Music]

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