Understanding the Structure and Function of the Cell: A Comprehensive Overview
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Introduction
Welcome to an in-depth exploration of the structure and function of the cell! In this article, we will cover the key components of the cell, their unique structures, and the vital roles they play in the cellular environment. Understanding cell biology is crucial for grasping how various life processes are interconnected, so let’s dive in!
The Nucleus: The Brain of the Cell
The nucleus is often referred to as the brain of the cell due to its role in regulating cellular activities and housing genetic material. Let’s break down its key components:
Nuclear Envelope
- Structure: The nuclear envelope consists of two membranes: an outer and an inner layer.
- Function: The outer layer is studded with ribosomes and facilitates the transport of mRNA from the nucleus to the cytoplasm through nuclear pores.
Nuclear Pores
- Description: These are protein complexes that span the nuclear envelope.
- Function: They regulate the exchange of materials such as ions, proteins, and RNA between the nucleus and the cytoplasm.
The Nucleolus
- Function: It is responsible for synthesizing ribosomal RNA (rRNA) and assembling ribosomes from rRNA and proteins, which are then sent to the cytoplasm.
Chromatin
- Composition: Chromatin consists of DNA and histone proteins.
- Types: There are two forms of chromatin: euchromatin (loosely packed, active in transcription) and heterochromatin (densely packed, inactive).
- Roles: It is crucial for the processes of DNA replication and transcription.
The Endoplasmic Reticulum (ER)
The endoplasmic reticulum is a membranous network involved in a multitude of functions within the cell.
Rough Endoplasmic Reticulum (Rough ER)
- Description: The rough ER has ribosomes on its surface, giving it a rough appearance.
- Functions:
- Protein Synthesis: The rough ER synthesizes proteins destined for secretion, incorporation into the cell membrane, or for lysosomes.
- Protein Folding: It also assists in the proper folding of proteins and post-translational modifications such as glycosylation.
Smooth Endoplasmic Reticulum (Smooth ER)
- Description: Smooth ER lacks ribosomes.
- Functions:
- Lipid Synthesis: It synthesizes lipids, including phospholipids and cholesterol, which are essential for membrane integrity.
- Detoxification: The smooth ER metabolizes drugs and toxins, especially in liver cells.
- Calcium Storage: It plays a role in storing calcium ions, particularly in muscle cells, aiding muscle contraction.
The Golgi Apparatus: The Shipping Center
The Golgi apparatus plays a critical role in modifying, sorting, and packaging proteins and lipids from the ER for delivery to their intended destinations.
- Cis and Trans Face: The golgi has a cis face (receiving side) and a trans face (shipping side), facilitating the movement of vesicles.
- Functions:
- Modification: Further modifies proteins through glycosylation.
- Packaging: Packages proteins into vesicles for transport to lysosomes, the cell membrane, or secretion outside the cell.
Mitochondria: The Powerhouse of the Cell
Often referred to as the powerhouse of the cell, mitochondria are essential for energy production.
- Structure: Mitochondria have a double-membrane structure with an inner membrane that folds into cristae, increasing surface area for enzymatic reactions.
- Functions:
- ATP Production: ATP is produced primarily through oxidative phosphorylation, utilizing the electron transport chain.
- Metabolic Pathways: Mitochondria are involved in the Krebs cycle, fatty acid oxidation, and other metabolic pathways.
The Cytoskeleton: The Cell's Framework
The cytoskeleton provides structural support and aids in cellular movement. It consists of three main types of fibers:
Microfilaments
- Composition: Primarily made of actin.
- Functions:
- Muscle contraction in interaction with myosin.
- Facilitating cell shape change (e.g., during cytokinesis).
Intermediate Filaments
- Function: Provide structural stability and resist mechanical stress, anchoring organelles in place.
Microtubules
- Composition: Made from alpha and beta tubulin.
- Functions:
- Intracellular transport via motor proteins (dynein and kinesin).
- Cell division, aiding in the separation of chromosomes during mitosis.
- Formation of cilia and flagella for cell motility.
Lysosomes: The Cell's Cleanup Crew
Lysosomes contain hydrolytic enzymes responsible for breaking down waste materials and cellular debris.
- Functions:
- Macromolecule Breakdown: Enzymes like proteases and lipases break down unwanted biomolecules.
- Autophagy: Involved in recycling cellular components.
- Autolysis: Can release enzymes in damaged cells to facilitate self-digestion.
Peroxisomes: The Detoxifiers
Peroxisomes contain enzymes that detoxify harmful substances and help metabolize fatty acids.
- Key Enzymes: Include catalase and oxidase, which convert hydrogen peroxide into water and oxygen, preventing oxidative stress.
Conclusion
In summary, the cell is a complex and dynamic unit that relies on the interaction of various organelles, each with specific structures and functions. Understanding these components is essential for grasping how life operates at a microscopic level. From the nucleus directing cellular activities to lysosomes managing waste, each part plays a crucial role in maintaining cellular health and functionality. Thank you for exploring the fascinating world of cell structure and function with us!
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
please continue to support us by hitting that like button commenting down in the comment section and please subscribe all
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
the nucleus now what we have to talk about with the nucleus is a couple different components of the nucleus what
you can see you see this kind of like blue membrane that's double layered here so you have an outer layer
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
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
pores so what are these called nuclear pores and the whole purpose is it's honestly pretty straightforward right if
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
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
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
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
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
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
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
and that is called transcription and then also you need to know that there's different types of rna what are the
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
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
called mrna and that mrna then binds with a ribosome here's our ribosome a little like red
taking the rna and making proteins well what happens is that ribosome it's going to start synthesizing and making
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
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
and get incorporated into the different organelles like the membranes of organelles or the cell membrane
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
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
like cosylation and there's a particular type we'll go into this more in more detail but for the most part it is
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
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
kind of gone through this process of synthesizing it folding it and then glycosylating it it then has to package
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
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
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
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
we're going to have the smoothie r take the precursor molecules perform the lipid synthesis process with the enzymes
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
so you know whenever your liver your liver has a very high concentration of these enzymes because that's our detox
and what your liver does is is it undergoes a process called biotransformation or xenobiotic
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
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
is that this actual smooth endoplasmic reticulum is also important for glucose 6-phosphate metabolism so it's also
endoplasmic reticulum it's in in a lot of different organs but you know organs that contain lots and lots and lots of
sarcoplasmic reticulum these can store lots of calcium and you know there's little pumps that
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
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
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
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
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
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
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
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
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
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
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
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 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
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
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
and they contain very interesting little enzymes inside of them and these enzymes are called hydrolytic
proteins you have nucleases which means that they break down nucleic acids you have lipases which means they break down
carbohydrates so all of these hydrolytic enzymes are located within these little organelles
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
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
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
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
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
and they contain a lot of different enzymes but by far one of the most interesting enzymes that they contain
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
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
here all of these molecules are free radicals very dangerous little suckers can bind onto proteins and nucleic acids
the particular one that loves to accumulate though in these peroxisomes because of what's called fatty acid
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
because this is also important for making different types of hormones steroid hormones and bile acids
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
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
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
permeability there's a lot of transport proteins on the outer membrane if you look here you have this little
and usually on most cells we call this inner membrane the folding chris stay we call it the chris day of the inner
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
when we make atp we make it in two primary ways one is called oxidative phosphorylation the other one is called
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
metabolic reactions that occur here a lot of metabolic reactions what are some of these metabolic
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
is you have heme synthesis so you're making the heme component of different types of uh
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
so these are some of the metabolic pathways that occur within the mitochondria one other thing to remember
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
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
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
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
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
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
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
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
constriction ring and eventually squeeze it to the point where guess what happens you butt off from one cell
you know white blood cells if you take a white blood cell let's imagine here i have a white 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
white blood cell wants to be able to squeeze through those actual capillaries what is that called
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
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
and what happens is i create these like little arms or little extensions that come out here to
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