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Centrosome and Centriole

welcome back friends welcome to another

video from somos biology in this video

tutorial we're going to talk about the

structure and function of centrosome and

centrioles okay so let's look at it

centrosome I already draw the structure

of centrosome centrosome is a structure

consisting of two things one is the

centrioles another one is the PCM or PD

sensual material now centrioles are

nothing but the barrel-like structures

made with microtubules now the question

is what are microtubules microtubules

are the structure of cytoskeleton that

are made with of tubulin proteins tbling

dimers you know there are different

types of tubulin proteins like alpha chi

moving peach are tubulin so those

tubules are combined to get the tools to

make a chain or once those tubules are

polymerized like a chain it will form

microtubules

so such microtubules are organized with

each other arranged with each other like

a barrel shape and you will form what is

known as central in the sensual we have

such two barrels present in a 90 degree

angle with each other now this is the

sensual part now the sensual is

surrounded by a dense material the

material composition is just like the

cytosolic composition but it is a little

bit more dense

now that why it is more dense because it

contains so many different protein

molecules in that area what kind of

proteins proteins examples gamma tubulin

lining very centering so these are the

examples of protein that are found you

know all these proteins like gamma t

building 9 in paris centering they found

in this PCM because they help the

microtubules to grow that means they

help in the organization of those

tubulin dimers with each other to make

the microtubules present so if you look

at look at the structure you know in the

PCM we have those protein particles

denoted with this red dot and not only

that we also have a position from where

the microtubules originated so this

black

lines represents the microtubules

radiating from the centrosome structure

and you know if you look at here they

are simply polymerization reactions one

after another so if I draw the structure

it will be like like say alpha and beta

tubulin and then again alpha beta alpha

beta so once tubulin dimers are attached

one after another it is following what

is known as a microtubule this is called

the microtubule now here you see the

microtubules coming out from the central

section and the microtubules you see two

different regions for that because

microtubules are polar they have a

negative end and a positive end now

negative end are minus any means

where from where the microtubules get

dissociated while positive ends means

from where the microtubules get

associated so new tubulin dimers start

with from the plus end and the

dissociation of the tribunes start from

the mind send this is the idea of

microtubules that are originated now the

function of centrosome and centrioles is

to produce microtubules and why

microtubules production you know to

guide these microtubules to interact

with the centromere region kinetochore

region of the chromosomes during the

cell division because in during the cell

division process we need to separate the

sister chromatids from each other in the

mitosis cell division and that thing is

controlled and regulated by the

microtubules and the production of

microtubules is controlled by

centrosomes

now this centrosomes and sensual this

whole idea is very common only for

animal cells because in course of plant

cells and fungi we don't see centrosomes

much and actually not at all

animal cells contain centrosome and

think real structures or this process of

cell division now the question is if

plant cell don't have this centrosomes

and central structure then how could

they divide now the answer for that is

if pretend what turns out that they

don't have central zones but they have a

similar structure known as Mt

Oh see the full form microtubule

organizing Center now MTA OSI is very

similar like the central zone but they

are lacking this sort of central zone

peril or sensual barrel microtubule

barrel-like structure what in turn they

have there

but this region where they have some

proteins which are responsible for the

arrangement and polymerization of

microtubules polymerization of tubulin

molecules to make microtubules that is

the idea now the structure of central CP

going deeper as I told you they are

present in a 90 degree angle and the

structure is like the barrel if you look

at the barrel this this barrel is made

up with you know cartwheel model we call

them as a cartwheel model what is

carving model is that if you take this

triplet normally normally this barreling

this barrel there are nine microtubules

present nine such microtubules arranged

three four five six seven eight nine

they're arranged if I do the cross

section nine such microtubules are

arranged and all those microtubules are

consisting of three two beauties three

tip you leaves every one contains three

T buildings with each of it just like

that let's say these are the 30 billion

setters with each other and I take it as

a unit and I could each unit there so

it's a it's a nine microtubule triplet

that represent triplet means three such

same molecules are attached with each

other so nine such triplets are present

and attached with each other and they

are attached by interactions in between

and they also have a central pair it's

not it sort of triplets the duplet that

the central pair will interact with the

help of proteins known as spokes so it

looks like a wheel it's known as the

cart wheel model so this is the

cross-section if you look this is the

cross-section and this is how it looks

like so this structure is only found in

animals about the centrioles and

centrioles present in the 90 degree

angle now the question is how they help

in the cell division you know in the

cell division process this centrosomes

are present in one place of the same one

only one centrioles is one centrosome is

present per cell

now before cell division that is before

the chromosomal segregation that is the

inner phase you know even before the

metaphase during the inter phase of cell

division the centrosomes divide and make

itself twice so from one centrosome two

centrosomes are developed why because

for the separation of the crew

see pie if ideas that explain about how

chromosomes are separated it will be

more clear for you to understand so let

us say these are the chromosomes which

are already being duplicated and

microtubule organizing centers or

centrosomes whatever you know whatever

you think of they are present in this

area let's say like that and

microtubules are originated from them so

it will try to grab this chromosomes in

the kinetochore region that is the idea

right see if we want to grab to the

kinetochore region if so this is the

black thread once is attached then you

will drag them in the opposite

directions for that the the sister

chromatids get separated from each other

now for this whole process they also

need some other motor proteins to to

help in this dragging there are other

proteins out there like kindness in in

timing but in this case in this case of

the separation they also so in that case

you know you need two centrosomes to be

present in the opposite pole of the cell

for this segregation to occur properly

but we know the cell has one centrioles

so they need to divide the centrosome so

they in the interface in the interphase

cells divide their centrosome sense

dividing the centaurum into two

different parts so from one centrosome

it makes two centrosomes okay but they

are joined this this area of central

servers are not separated till now but

just before this segregation like like

the late made up is cell cycle late

metaphase that means in the metaphase

you know the chromosomes are aligned in

the center the region of the cell called

the metaphase plate now at that time

this portions of the mother sensual

mother sensual is essential that

represent earlier the parent one the

mother sensual and this is known as a

daughter sensual so then during that

process this mother central gets

separated from the daughter centrosome

so then then the mother centrosome when

daughter centrum slowly start to migrate

to the opposite poles they will migrate

to the opposite poles so as

a migrated to the opposite poles and

they are attached with the chromosome

with the kinetochore region then they

will start the separation now after the

separation is properly complete what

what structure we can achieve we will

see that this chromosomes are separated

and after the chromosomes are separated

then there will be situ kindnesses which

will be the division of the cytosol and

the separation of the cell into two

daughter cells so that is the idea of

cell division and for that reason we

need two different centrosomes in the

opposite poles now the question is in

case of plants if they if you don't have

this we have them toc doing the same job

now the question another question is

that this the presence of the

centrosomes are not that vital or

necessary for the for the process of

cell division for the survival for an

organism now what we do even in some

cell division process even if we delete

even if we destroy the centrosome

structure still we saw there is no much

difference in the cell division process

no much delay in the cell different cell

division processes that tells us one

important thing that this process of the

presence of centrosomes are not that

vital for the cell division but the

presence of microtubules are definitely

vital the presence of microtubules is

much required definitely required by any

means if there is a microtubule

organizing Center formed in the cell

that will definitely help the cell to

divide but it's it not always necessary

that you should have centrosomes in the

cell so that is the idea of centrosomes

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