L8 : Cell Membrane - Cell Biology, Science, Class 8 Video Lecture

hello friends this video on cell path
eight is brought to you by exam feel
calm no more fear from exam so now it is
first discuss cell membrane so what does
stand in it now first of all cell
membrane is also known as class for
membranes these two terms are often used
interchangeably so please do not get
confused cell membrane and plasma
membrane mean the same thing so it is
also called cell membrane and it is a
thing there you keep living outermost
covering of cell so the primary why we
have the cell membrane so the primary
function is definitely protection
because it is like a covering it is like
the boundary of your house so why do you
give a boundary to your house because
you want to protect your house so in a
very similar way this is also a thin
covering but it is living it is not a
dead membrane so this cells which form
the milk and the boundary of the cell is
also living now how do we define
something is living and something is
nonliving something which is living will
undergo the various metabolic activities
for example restoration will have a lot
some of activities will keep on
happening which shows that it is living
it provides shape to the cell that is
another important function of the cell
membrane
now we why we were talking about the
shape of cells I told you that different
cells have different shapes some are
spherical size along with some a spindle
shape some of them even change their
shape now who decides the shape of the
cell it is decided by the cell membrane
because the way the boundary is the way
the shape of the cell will be so if I
say that the boundary is going to be
like this then this is how the shape of
the same will be if the boundary is like
this then this is how the shape will be
if the boundary is like this again the
shape will be like so boundary decides
the shape of the cell it also ensures
protection to the same because of course
it is the boundary so it will only allow
it will not allow any part of
inside the cell it will selectively
allow only the necessary particles to
get inside the same so we will talk
about that property of cell membrane
also so here as I have mentioned before
this is the cell membrane and this cell
membrane keeps each cell distinct on
impact from other cells so you see if
this cell membrane it actually is
protecting this cell right so it is
keeping this cell separate from all
these dead so these are also sent all of
them are separated from each other due
to the presence of cell membrane so here
in plant cell this is your cell membrane
or plasma membrane it is a selectively
permeable membrane now I want to be
moved mean by selectively permeable
membrane but label means something which
allows substances to pass through it
that is what permeable so if a
particular wall allows particles to pass
through it then it is permeable if it
does not allow then it is non permeable
now what is the meaning of selectively
permeable that means it is very
selective in allowing particles to pass
through it it allows certain particles
to pass through it but it doesn't allow
certain particles to pass through it so
that is why it is selectively permeable
so it is something like your security
guards so your security guards which are
present in that may be you are standing
at the gate of your house they might be
selectively permeable because they allow
people who are your friends to enter
your house but they do not allow
strangers so that means they allow some
people they do not allow some people so
similarly plasma membrane is also
selectively permeable so let us discuss
the selectively permeable nature of the
plasma membrane in little more detail
so now what governs the movement of
substances in and out of the cell
because this is the boundary
membrane is the boundary so it has to
decide which particles should go out of
the cell and which particle should enter
this it because it should not happen
then derived particles are going out and
the wrong particles are coming in so how
will it decide now there are two
processes which take place and with
these two processes exchange of
substances happen between the cell and
the external environment so one process
is diffusion one is diffusion it is the
gaseous exchange between cells as well
as cell and its external environment so
that means when would gaseous want to be
exchanged between two cells now there
can induce analysis one cell this is
another cell so this is the cell
membrane of one send this is the cell
membrane of another cell
so now particles might be exchanged
between these two cells that is one
scenario there is another scenario this
is one cell and the particle mind gets
exchanged between the cell and external
environment so who will decide whether
the particle can move on or the particle
can come in so that will be decided by
the cell membrane so the process by
which this exchange happens that is
going to fusion so conclusion is
applicable only for exchange of gases
like oxygen or carbon dioxide they might
with exchanged between two cells or
between one cell and its external
environment and that process is one
diffusion another process is osmosis
which governs the exchange of water so
what are the exchange between cells as
well as cell and its external
environment so whenever it is about
movement of gases then the process is
diffusion whenever it is about movement
of water then the process is all sources
now what happens in diffusion and
osmosis is the movement of particles
whether it is gases or it is water it
happens from a region of higher
concentration
towards a region of lower concentration
that means let us suppose this is cell
one and this is sending okay now we are
for now let us assume that the
concentration of oxygen is high in selma
and the concentration of oxygen is low
in cell tone so how will the movement of
oxygen take place so oxygen will always
move from region of higher concentration
towards region of lower concentration so
oxygen will move from cell one to send
to so very similarly if the
concentration of water is more in one
than into the movement of water will
also take place from region of higher
concentration to region of lower
concentration so in both these processes
whether you talk about diffusion or
gauss horses movement takes place from
region of higher concentration towards
region of lower concentration so this is
the basic principle of diffusion and
osmosis so let us talk about diffusion
first here movement of gases like carbon
dioxide and oxygen from region of higher
concentration towards a region of lower
concentration so let us take this
example that is suppose this is a cell
now so let us consider the scenario in
the first scenario we have just one cell
so here we will see the interaction
between the cell and the surrounding so
this is cell and this is the surrounding
and here in the second scenario we have
cell one and cell two so there are two
cents
now in this case let us suppose that is
the concentration of carbon dioxide
is more in the surroundings and here the
concentration is all in cell 1
so what will be the direction of
movement of carbon dioxide from
surroundings to send because it moves
from I get concentration towards lower
concentration similarly in this case
here also carbon dioxide will move from
cell 1 cell 2
so this is how diffusion takes place in
through the cell membrane now let us
suppose if it is vice versa if the
concentration of carbon dioxide is rule
inside the seasoning to move out to the
surroundings here also if it is more
insane to then if it move from cell to
cell in one let us now talk in a similar
way about osmosis so it is going to be
the same concept just that instead of
gases here we have water so here a
movement of water will take place from
the region of higher concentration
towards an eg a lower one so in the same
thing you have a cell here and here you
have cell one and cell 2 if the
concentration of water is or outside
then if the movement will take place
from outside to inside so in this case
what will happen the cell will spell it
out because more water is a clean inside
the cell so it will start reading up in
this case what will happen send one will
start shrinking xl2 will start reading
one but if it is just the opposite that
is simply saying that the concentration
is more inside misstep or its end - then
water will start moving out of the cell
here and water balloon frozen - to cell
1 so whichever cell is gaining water
will swell up and whichever cell is
using water will shrink so with these
concepts and by let us see the behavior
of a cell with different types of
solution so let us suppose if the cell
is put in a solution which is a hypo
donning solution want to be mean by IQ
toning solution that means the
concentration of water change water
concentration in the solution is highly
respect means inside the cell water
concentration is less then it suppose
this is the hypotonic solution where
water concentration is more and this is
the same so water concentration is more
in this case where water concentration
is more outside so that means water will
move from outside to inside as a result
the cell will start speeding up
so whenever a cell is put in a
hypertonic solution what happens to the
same the same suelze similarly if it is
just the opposite that is if you put it
in hypertonic solution that means a
solution where water concentration is
less than that inside the cell now
hi-pro hypo means less hyper means goal
so hypertonic solution means water
concentration is more inside the cell
okay so here if you see this case what
will happen
so here the concentration is less so
that means water will move from inside
to outside saying this is the cell will
gradually shrink because the cell is
losing water so this is how it will
behave now if we take an isotonic
solution I'm so insane that means the
concentration of water in the solution
is same as the concentration of water in
the cell so who would silence the
concentration is the same so in this
case there will be no movement at all so
water will either move outside or with
it will enter inside so then stain the
ligand as it is there will be no sparing
or shrinkage so based on this we got to
know that plasma membrane or said memory
performs two important function one is
it provides shape to this day second it
allows certain particles only to pass
through
now let us look at the structure of
plasma membrane what is the class of
membrane made up of when it is made up
of lipids and proteins now you might ask
what are lipids lipids are organic
substances that has carbon containing
substances which argue soluble in water
so lipids are you can think they're
gluten solidity facts because facts are
also insoluble in water so lipids are
also insoluble in water so lipids and
proteins they are the constituents of
them plasma membrane so it can be seen
through an electron microscope so you
really mean a powerful microscope to
look at the structure of the plasma
membranes here you see this boiling
planet boundary is the plasma membrane
but when you look at it through an
electron microscope you can actually see
that it contains two layers of lipids so
this thin line which we normally see is
not a thin line actually has two layers
of lipids so when you see it with a very
powerful microscope only then you will
be able to see so because of this it is
hard you have a simple bilayer structure
because it has two layers of limits and
then where the proteins located the
proteins are embedded in these lipid
layers so let us quickly look at the
lipid bilayer structure so this is how
it will look like this is one layer of
lipid this is one layer of lipid so
these are the two layers of lipids so
his I hit bits now I do not want to get
into the detail of the lipid bilayer
structure because we would step on these
in your higher classes but it is you are
inclusive about it you can refer to the
reuse of cell of
eleven so these are the two layers of
lipid and the protein molecules are
embedded somewhere here's the protein
oily foods will be invaded in this
bilayer structure so this is a
continuous by layer of liquid molecules
and this is why it is also known as the
fluid mosaic structure so that is also
another name of this morning it is also
called fluid whose a structure now here
I think this much of information is
enough about cell membrane and rest of
the details we will discuss in higher
class so proteins are embedded in
continuous bilayer of lipid molecules as
I said just now so these are two layers
of lipids and these structures are the
proteins thank you please visit
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