Intracellular Organelles- The Centrosome

welcome to this tutorial where we are

going to be taking a quick look at an

intracellular structure we have called

our centrosome and centrioles that go

along with it so before we even start we

can say that our centrosome is an

organelle within the cell despite it not

being confined by its own lipid bilayer

so we have our cell here with its

nucleus and the cytoplasm outside of our

nucleus now what is our centrosome and

where are we going to find it within the

cell well we're going to find it in the

cytoplasm and I'll just put it up on the

screen here so this is going to be our

centrosome here well this is actually

going to be two centrosomes and what

they do within your cell is organized

your microtubules which is part of your

cytoskeleton of the cell and they're

also going to be where you construct

microtubules so organization and

construction and we can think of our

cytoskeleton simply as cell skeleton or

what's giving the cell its structure and

form now if we zoomed into these

centrosomes that are within our cell

we're going to find that it will look

something like this

so it's this fairly odd-looking

star-shaped like structure that there

are two of grouped together and we call

the individual units of the centrosome

centrioles so each one of those

star-like structures is called a

centriole I'll just write that here so

we have two centrioles that make up our

centrosome and they're going to be

arranged at right angles to each other

and this right angle formation has to do

with how our centrosomes are created but

we don't really need to focus on that

right now we just need to know the basic

function of our central zone

centrioles so just know that they're

arranged at right angles to each other

and that we have two centrioles within

our centrosome now before we get too

carried away with what the centrosome

does let's focus quickly on what the

structure is so our individual

centrioles are going to be composed of

nine Triplets of microtubules and when I

say triplets what I mean is a grouping

of three so we can see here that we have

three microtubules per triplet in this

star formation of this centriole so we

know so far that our centrosome is going

to be responsible for organizing and

generating the new microtubules of our

cytoskeleton but we don't know what else

it does and for us to talk about that we

need to discuss our cell cycle so if I

bring up this diagram here of our cell

cycle with its different phases so I'll

just put in our g1 phase our first

growth phase our g2 phase and our M

mitotic phase the first thing we need to

know is that usually within the cell we

only have one centrosome so I'll remove

that second one I put there for the

moment within the cell so we've only got

one centrosome most of the time within

our cell but when it comes to the S

phase of the cell cycle we're going to

replicate our centrosome and we

replicate it from the existing

centrosome now remember that S phase is

the same time that we're replicating our

DNA as well now if we're replicating it

from the pre-existing that means just

like our whole cell we're going to have

a mother and daughter centriole and from

there is where we'll create our second

centrosome which we'll talk about when

we talk about the centrosome cycle so

we're past that point now in the S phase

of our cell cycle where we replicate

centrosome and we have to and when we

have two centrosomes within our cell

it means we're preparing for cell

division or the mitotic phase so we have

our two centrosomes now and when it

comes to your mitotic phase your two

centrosomes that you now have within the

cell are going to be responsible for a

huge part of mitosis which is the

formation of the mitotic spindle and in

our mitosis tutorials we will talk about

the mitotic spindle a lot more but the

last thing I want you to be aware of

although I've mentioned it already is

the anchoring and generating role of new

microtubules that are centrosomes have

and if we were to look at our cell under

an electron microscope we would see that

our cytoskeletal microtubules are

extending out from the centrosome with a

very dense population right near the

nucleus and this is their location where

we will find our centrosomes so we can

see all of those microtubules are

becoming very dense toward the nucleus

and the centrosome so now we know all

the basics about our centrosome and

centrioles and can develop a deeper

understanding of what will be happening

when we begin to discuss mitosis and as

always I hope this video has been

helpful to you thanks for watching and

I'll see you again soon