Plasma Membrane: Fluid Mosaic Model, function Video Lecture - NEET

hello friends this video on sell the
unit of life part 10 is brought to you
by exam four calm no more fear from exam
now the structure of plasma membrane the
widely accepted structure of plasma
membrane is given the name of fluid
mosaic model now you might be wondering
why such a fancy name for the structure
of plasma membrane fluid mosaic model so
we will talk about it and then we get to
know by this name this model was
postulated by two scientists named
singer antony carlson and they described
this model as protein icebergs in the
sea of lipids so lipids all around and
then that proteins are present here and
there so that is how they described it
so if you have a sea and in that sea you
have icebergs which are like quite big
and they are either on the surface of
the sea or inside the sea
similar is the case here proteins can be
either inside or on the surface of the
lipids so this is how the structure is
the structure which I explained you just
now so in this case proteins are neither
confined only to the surface nor do they
form continuous layers so that is one
speciality of how proteins are
distributed here so you cannot see that
okay they have default continuous layers
on the surface no sometimes some of them
are on the surface whereas some of them
are inside some of them are partially
buried so proteins are a randomly
distributed so they are basically
distributed in a mosaic fashion mosaic
you know right you would have heard of
this doing mosaic on the floor what is
that just it is like random distribution
of those colored stones on the floor let
us go to mosaic so here also proteins
are distributed randomly neither on the
surface nor completely below the surface
so that's why proteins are distributed
like in a mosaic pattern that is why the
term mosaic
now why is the term fluid now fluid is
because of the fluidity of the membrane
now this a plasma membrane which you see
it is not static here the lipid
molecules which you see all these lipid
molecules are linked to one another by
bonds which are very very weak Yassin if
the bond is very weak then they can move
laterally let us suppose if you have two
objects which are tied by a very thin
thread and you if you have the same two
objects tied by a thick rod in which
case the possibility of the objects
being moved is more suppose now if wind
blows what will happen this thin thread
might get carried away by the wind so
these objects might move but this thick
rod will not be carried away by the wind
so this will not move so if the bond
between the lipid molecules is really
really weak in that case there is a
possibility that the lipid molecules can
move laterally and that is what happens
here in this membrane also since the
bond joining the lipid molecules are
very weak then what the membrane is not
static and it moves laterally now
mobility is more and it is generally
observed that the mobility is even more
in membranes which have lesser
cholesterol it is not only the lipid
molecules which can move it has been
found that the proteins can also move
but much lesser than the lipids so the
movement in the protein molecules are
not that evident but yes the lipid
molecules do move because of that this
membrane has a fluid nature what is
fluid anything that can flow this fluid
now since the lipid molecules can move
this I mean this side also you have
lipid this side also you have
the bets and they all can move laterally
so if everything is moving you will feel
as if it is flowing and that is why it
has said to be a fluid mosaic model
fluid because the lipid molecules can
move laterally due to the weak bonds
mosaic because the proteins are arranged
in a mosaic pattern that is why is the
name fluid mosaic model so this
arrangement or this structure of plasma
membrane is popularly accepted and
popularly known as fluid mosaic model
now as I just discussed structure of the
plasma membrane is not static fluidity
of the membrane is present so membrane
has a fluid nature now I also give you
certain instances which will help you to
understand it better that yes like when
I say for the first time that the plasma
membrane can move it
it sounds little weird because you might
be thinking it is the boundary of a cell
how can it move a boundary is generally
don't move but when I give you some of
the instances or some of the activities
or functions of the cell which actually
gives a hint that the membrane is has a
fluidity
so fluidity of the membrane is important
for cell growth when I talk about cell
growth what happens the cell grows in
size now let us suppose if this is a
cell so that the cell grows in size like
this like this so what is happening
basically this cell membrane is also in
getting enlarged to accommodate the
bigger size of the same right you're
getting my point so that means there is
some amount of flexibility with the same
brain which is allowing it to
accommodate a larger cell that is
possible because of the fluidity of the
membrane because the membrane is able to
move laterally so it is able to adjust
the bigger size of the cell similarly
you talk about sent division what
happens in center vision when the cell
divides these plasma membranes need to
expand and quanta
during the cell movements involved in
cell division that is also possible
because of the fluidity of membrane
secretion so flow of materials through
the plasma membrane is indicative of the
fluidity of membrane now since the
membrane is like slightly movable
satisfying it becomes easy to for
materials to pass through it and also to
secrete substances formation of cell
junctions if you want to connect to
cells let us suppose this is one cell
this is another cell if you want both of
them to join there has to be some
flexibility from both the plasma
membranes and that is possible because
of the fluidity of the membrane so these
are some of the properties which favor
the fact that plasma membrane is fluidic
in nature to some extent so this was all
about the fluid mosaic model now that we
have completely understood the semi
permeable behavior of classify membrane
as well as the structure of plasma
membrane let us quickly look at the
functions which the plasma membrane
perform so the first and foremost
function is protection of the same this
membrane being the boundary has to
protect the same movement of substances
in and out of the cell when I say
substances it can be gases by diffusion
or water by osmosis and this movement
can also happen by active transport as
well as passive transport so depending
upon the need flexibility enables cell
to engulf food and other materials from
surroundings as I said since the
membrane is quite flexible the membrane
can move so movement of the membrane
also helps to engulf food for example if
you think of amoeba what happens in case
of amoeba the shape of the body is
irregular and it does not have a fixed
shape so you can change its shape let us
suppose let us suppose this blue colored
thing which you see here that is a food
material and this is the amoeba so what
it does it changes its shape as you can
see
here so what is changing it is not only
about what is changing but the boundary
is also changing the plasma membrane is
also changing and gradually changes its
shape in such a way that the food
material which was earlier outside has
come in as come inside so it has
engulfed the food material and this
became possible due to the flexible
plasma membrane now this process in my
bi is known as endocytosis so plasma
membrane these are some additional
functions which are performed by the
plasma membrane but the basic function
of plasma membrane is to ensure
protection of the cell and how does it
ensure protection of the cell by
becoming selectively permeable it does
not allow anything and everything to
pass across it so with this we will end
our discussion on plasma membrane I hope
the concept of plasma membrane or cell
membrane is now clear to you this plasma
membrane is found in all types of cells
whether it is plant cells or animal
cells in fact when we will talk about
prokaryotes they are also you see plasma
membrane is present so with this we'll
end our discussion on plasma membrane
thank you please visit www.payoor.com
to watch more videos attempt free online
test
get free study material find tutors and
mentors thank you once again