Structure of cell- Plasma membrane - Fundamental Unit of Life, Force & Laws of Motion, Science, Class 9 Video Lecture

hello friends this video on the
fundamental unit of life part 5 is
brought to you by exam feel calm no move
here from exam the mouth starts our next
topic that is the structure of sin now
let us see how actually was the
structure of a cell observed or how can
we even now observe the structure of a
cell so let us try to experiment with a
sample of onion peel right so watch your
kitchen take an onion and just cut out
the feel of it so you take the peel of
the onion and please it until them
microscope in your science lab right so
what happens when you observe that onion
peel with the help of the microscope you
see a structure like this a structure
similar to this right so you see these
kind of a structure so looking at the
structure three important components of
the cell are observed so what are the
different components you see the each of
these small roots which are enclosed by
walls are known as says so this is 1 2 3
4 5 6 7 8 so these are all cells right
in the onion P now if you see each of
these cells have this wall which
encloses the cell so this wall is known
as the plasma membrane so this covering
of the cell is known as plasma membrane
right now inside the cell you have
something which fills the space inside
the cell so that is a fluid like
structure which is known as cytoplasm
plasm always refer to some fluid in
structure right so this is known as
cytoplasm and you would also see that
inside every cell you have a dot like
structure somewhat like this so in every
cell in this picture to sort very clear
it in every cell
but inside every cell you have a dark
structure comparatively darker than the
rest of the same length then the rest of
the cycle
you have a relatively damper structure
that is known as the nucleus of the set
so these are the three major or the
three most prominent structures of the
cell so broadly cells structure is
divided into these three parts cytoplasm
nucleus and plasma membrane other than
these you have the different components
of the cell known as the cell organelles
cell organelles are the different
components which are present inside the
cell somewhere in the cytoplasm right so
we will talk about this in cell organ
organelles after we discussed these
three important constituents of cell
right so when I talk of the structural
organization of a cell what are the
components which I spoke about plasma
membrane which I just told you the outer
covering right the next one is the cell
wall so that cell wall is an additional
covering which is present only in plant
cells then you have the nucleus you have
the cytoplasm and then you have the
different cell organelles right so now
we will start with plasma membrane right
as I mentioned first we will complete
these three important constituents that
is plasma membrane nucleus and cytoplasm
after that we will talk about each of
the cell organelles so let us see what
does a plasma membrane plasma membrane
is also known as cell membrane so
sometimes you see that many of the
textbooks will use the word cell
membrane instead of plasma membrane so
it is a thin delicate living outermost
covering of a cell so it is a thin
covering it is very delicate not very
rigid and hard and it is living it is
not a dead covering it is living it has
life so it is a thick dedicate living
outermost covering of them said it
ensures protection of the set obviously
I mean it is like a wall for example
when I stay inside a room I feel
protected because I am surrounded with
on all sides by one's right similarly
the cell protection is ensured by the
outer covering that is
plasma membrane when we look at the
microscopic view of the onion beam we
can see the plasma membrane very
prominently so discovering of the empty
spaces
so these doubling of the empty spaces
are nothing but plasma membrane right
okay now when I look at this cell what
is this what does this picture this is
nothing but an animal cell an animal
cell looks like this so what are these
so many things which are present inside
the same these are the different cell
organelles we talk about each of the
organelles one by one so right now I am
talking about the plasma membrane so
this is my plasma membrane right okay it
is a selectively permeable membrane so
that's interesting to know what is
selectively permeable what do I mean by
selectively permeable when I say quickly
permeable fully permeable means that the
membrane allows everything to pass in
and pass out so that means anything can
move in and out of that membrane so that
is known as fully permeable membrane
when Isis selectively permeable that
means it selectively allows certain
things to move in and move out at the
same time there are certain things which
it does not allow so it selectively
allows things to move in or out across
the membrane so we will discuss in
detail about this selectively permeable
membrane how is plasma membrane a
selectively permeable membrane let us
understand this fat so when I talk about
selectively permeable membrane we are
actually going to talk about movement of
substances in and out of the cell
because plasma membrane acts as a
boundary of the cell so whenever an
object wants to come inside the cell or
whenever an object wants to go out of
the cell it has to cross the plasma
membrane so here we will see how plasma
membrane allows things to pass through
them to pass through it now let me there
are two processes involved for the
movement of substances across the cell
is diffusion and the other one is
osmosis so what is diffusion diffusion
is gaseous exchange between cells as
well as cell and its external
environment diffusion means or orders
the world the fusion as such means it
means movement of gases from the region
of high concentration towards a region
of lower concentration for example it is
suppose there is some gas say oxygen so
it is suppose you have two different
medium let us suppose this is region one
this is region 2 so let us suppose here
the concentration of oxygen is higher
and here the concentration of oxygen is
less so what we have an oxygen will
start flowing from region one to region
two so it will start flowing from region
of higher concentration towards region
of lower concentration so this process
is known as diffusion so diffusion is
one of the moves by which plasma
membrane allows gases to move across it
so gaseous exchange between cells let us
suppose if there are two cells routes
between concentration of gases so the
gas will move from the cell with higher
concentration towards the same with
lower concentration or it returns
between the cell and its external
environment there also it will follow
the same rule it will move from higher
concentration towards lower
concentration and what does osmosis it
is water exchange between sense as well
as cell and its external environment so
the process remains the same just that
for gaseous exchange we use the term
diffusion and for water exchange we use
the current osmosis
so plasma membrane is a selectively
permeable membrane that means it will
not always allow anything to move from
any side to any side
it will only allow gases or water to
move from the region of higher
concentration towards the region of
lower concentration right so we will
talk about it in a few more detail so
let us first talk about diffusion so
what is diffusion movement of gases like
carbon dioxide and oxygen from a region
of higher concentration
towards a region of lower
saturation from high to low right let us
look at this Sonali let us suppose this
is that in the first scenario we have
the animal self so this is the cell and
in the surrounding it is external
environment now let us suppose that the
concentration of carbon dioxide is more
in the surroundings and that he in this
scenario the concentration of carbon
dioxide is gold in this step so in this
case what will happen carbon dioxide
will flow from region of higher
concentration to oxygen or lower
concentration so this ad or the blue
arrow shows us the direction of
diffusion in which direction co2 will
diffuse right so in this case the the
plasma membrane will allow the carbon
dioxide to move only along this
direction right now if it happens the
other way around
let us suppose that the concentration of
carbon dioxide is more inside the same
so therefore in this case in the first
example let us suppose the concentration
of carbon dioxide is more inside the
cell as compared to the surroundings in
that case carbon dioxide will start
diffusing
out that means it will start moving out
of the same similarly in this case if
the concentration of carbon dioxide is
greater in this thing so the carbon
dioxide will flow from this cell walls
this set right so this is the process of
diffusion similarly let us talk about
osmosis osmosis also the same thing will
happen but the just that institute of
gases will have water so movement of
water from a region of higher
concentration towards a region of lower
one so here also let me take a similar
example suppose the concentration of
water in the surrounding is more so what
will happen water will start entering
inside the cell correct similarly in
this case also when the concentration of
water is more here so what we will start
entering words in this region
similarly if it is the other way around
that means the concentration of water
inside the cell is more in that case
water will start moving out of the same
in this case also water will start
moving out of this sin and it will start
angling this same right okay now this
movement happens what is the cause of
this movement the basic cause of this
movement is the difference in
concentration that means if we have both
these cells with same amount of water in
that case what will happen
no osmosis will take place because both
of them are at them same concentration
nobody is at a higher concentration and
diffusion or osmosis will take place
only if there is a difference of in
concentration so that the gases are
watering and grew from reaching a higher
concentration what's lower concentration
right okay now let us look at the
behavior of a cell with different
solution so what we will see it is
suppose we take an animal cell and dip
it inside some liquid so how does it
behave how does the behavior of cells
changes if the type of the liquid
changes so let us first look at the
behavior with a hypertonic solution now
what does a hypertonic solution
hypertonic solution is a solution where
the water concentration in the solution
is higher than that inside the cell
right so that means the concentration of
water in the solution is more than that
inside the cell let us suppose if this
is my hypotonic solution so any solution
can have some water it when I say salt
solution that means well mixed with
water when I say so with sugar solution
that means sugar sugar mixed with water
select it is some solution where the
concentration of water is more as
compared to the cell so even inside the
cell you have more check you also have
water in the solution so when is a
hypotonic solution that means the water
concentration in the solution is again
right so in this case what will happen
flow of water will take place from which
direction to which direction as for the
principle of awesome
us water they move from higher
concentration towards lower
concentration now this is outside this
higher concentration and inside the Sen
is lower concentration right so how will
the water flow the water will flow from
outside to inside of the same now as
water
keep moving inside the cell what happens
the cell swells up right because you are
putting more and want more water inside
the cell it is like a balloon as you put
more and more water inside the balloon
what happens the balloon starts swelling
up so similarly when a cell is placed in
a hypertonic solution a water enters
inside the same as a result the cell
increases in size or the cell spend
summers whereas on the other hand when
it is a hypertonic solution that means
the water concentration in the solution
is lesser than that inside the cell
right so in this case what will happen
the concentration of water inside the
cell is more and outside is less so
water will flow from inside this and
towards outside right so this is how
water will move and as a result the cell
will decrease in size right so in this
case the cell will contract it and say a
balloon which has water inside if you
start taking the water out of the bed
what will happen the balloon will
decrease in size all right so the same
thing happens here in case of a
hypertonic solution now please remember
this when I say hypertonic solution hypo
means the word hypo means less that
means the concentration of water inside
the cell is less now let us talk about
isotonic solution what does isotonic
solution it means the water
concentration in the solution is same as
that inside the cell inside the cell and
outside the cell the water concentration
is the same so in this case what will
happen since there is no difference in
concentration there will be no flow of
water at all right
because osmosis will take place only
when
is a gradient in concentration whenever
there is a difference in concentration
so here there is no difference in
concentration so water will not so the
net result is that water will not flow
at all
correct okay now let us talk about the
structure of a plasma membrane now when
I stop talked about the structure of a
plasma membrane I am talking about only
this portion of the cell right so a
plasma membrane is made up of lipids and
proteins so now you must you are all
aware of what is protein you you would
have most of the times seen or more
masking you to have lots of pulses
because they have more proteins right so
you are aware of what proteins are but
what are lipids okay so he didn't talk
about lipids also they are related to
their some fat like structures all right
so we will talk about lipids quickly so
for now you understand that plasma
membrane is made up of lipids and
proteins the structure of the plasma
membrane can be seen only through an
electron microscope which has a very
good efficiency because the structure of
the in fact you cannot see a cell with
your naked eye right even because in the
cell so when I talk about the structure
of a plasma membrane
you obviously need an even better
microscope right the structure of plasma
membrane is often known as lipid bilayer
structure so we will talk about the
lipid bilayer structure in little more
detail okay so for now let us see what
are the bits because first we should
understand lipids in order to understand
the lipid bilayer structure so what are
lipids these are naturally occurring
organic substances which are insoluble
in water as I mentioned they are
something some fat like structures but
they are not fat see if its are
different from fats so these are
insoluble in water they are organic
substances water organic substances
substances which contain carbon so they
are carbon containing substances
in soluble in water now what are the
different functions that lipids perform
their help in energy storage they help
in cell membrane instruction which we
are talking about now they are also very
much useful in nanotechnology
do you know what is nano to Ponte you
would avoid many of your seniors we'll
be talking about these days
nanotechnology has got great value so
why I am going to do my engineering and
nanotechnology right so you have more
things like that so what is
nanotechnology this stick this is a
technology where you have where you deal
with extremely minut things right so we
are not going to talk about all these
things right now what I wanted to tell
you is I just wanted you to introduce
with lipids so what are lipids these are
organic substances insoluble in water
they help in energy storage they help in
cell membrane construction and also in
nanotechnology there are basically two
types of lipids nonpolar lipids and
polar lipids when I said nonpolar lipids
please and hydrophobic for big means
fear phobia you deferred right phobia
this this fellow has a great phobia for
ghosts that means he has fear for hosts
so hydrophobic hydrogen's water so
something which has fear from water that
is water hated so these nonpolar lipids
are water hater they do not want to
mingle with water whereas wet what are
polar lipids : if it's a hydrophilic I
fulfill it means water lover so these
are the two categories of lipids here we
will not talk about the structure of
nipples and we will not talk about their
examples in jeans at all because you
will learn in detail about lipids in
your organic chemistry in class 11 so
for now you should just know that what
are lipids so that I can talk about the
structure of the plasma membrane so
lipids there are certain categories of
lipids which have both hydrophobic as
well as hydrophilic end that means
hydrophobic a means one in heats water
the
the end loves water so these kind of
lipids are known as amphipathic lipids
and feelings more so it is both
hydrophobic and both and as well as
hydrophilic so such lipids are known as
and free parking lipids now when I talk
about the cell membrane structure we
will actually talk about the amphipathic
lipids that means the lipids which have
both hydrophobic end as well as
hydrophilic end let us look at some of
the examples of lipids for example
cholesterol a free fatty acids so you
have heard about cholesterol and fatty
acids in our day to day life we use
these terms for example we see that
butter has a lot of cholesterol so your
cholesterol level will increase so well
let's show us what exactly fat but it is
a struct it is an organic substance
which is insoluble in water as I
mentioned right so the spoiler also
helps to store energy but so these are
some of the examples of lipids so now
that and now let us try to understand
how the lipid bilayer structure is
constructed as I said the plasma
membrane is made up of lipids and
proteins right so how are the lipids
present here as and I also mentioned
that the lipids will share actually
needs of this plasma membrane and am
feedback pratik lipids that means they
have hydrophilic and as well as
hydrophobic and now here I in this
picture you can see this kind of
structures right now this stale
represents the hydrophobic end and this
head represents the hydrophilic end
right so here you can see that there are
so many lipids arranged in such a
fashion that their hydrophilic ends are
all together and this region represents
the hydrophobic region so the Olympics
are arranged in such a fashion that
these one n represents the hydrophilic
and so the hydrophilic end forms one
layer after that there is the region
which is hydrophobic region because all
of these lipids hydrophobic ends is
geared similarly all of these lipids
hydrophobic end is here so this forms
the hydrophobic region and again on this
end you will have the hydrophilic end
right so these are the alphabetic lipids
and all the sample fatik lipids are
embedded the protein molecules that
means on this you will have protein
molecules present like this so these are
nothing but the protein molecules which
are embedded on the lipid structure and
this is how a plasma membranes lipid
bilayer structure looks like why is it
known as a lipid bilayer because there
are two layers of lipids if you see this
is one layer and this is another layer
but basically how it is it is like two
layer of lipids their hydrophobic ends
add towards each other therefore there
is a hydrophobic region in between right
so I clear with the structure of the
plasma membrane okay so now proteins are
embedded in continuous bilayer of lipid
molecules so this was the bilayer of
lipid molecules and on this you have
proteins embedded in this fashion so
these are the proteins right okay so now
let us look at the structure as a whole
see this is how the structure will look
like these are the proteins these blue
colored structures are the proteins now
there are different types of proteins
again integral protein very federal
court protein so we are not going to
discuss about all those things now but
for now you should just understand the
basic structure of the plasma membrane
so plasma membrane is the outermost
covering it is made up of proteins and
lipids lipids there are two layers of
lipids which is known as the lipid
bilayer so the lipid bilayer in arranged
is arranged in such a fashion that all
the amphi all the hydrophilic ends are
together that these are the heads of the
lipid that is them I am super
hydrophilic ends and all the Hydra
Oh Big M sorry game together here you
can see these are the hydrophilic heads
so they are often called hydrophilic
heads and the other side is often called
hydrophobic tails X as a result this
region is shown as the hydrophobic
region and in this lipid bilayer are
invaded the protein molecules that is
why we see that the plasma membrane is
made up of lipids and proteins right so
we are clear with the structure of the
plasma membrane now let us look at the
function of the plasma membrane the very
first function is the protection of the
cell as I told you that it is an outer
covering of the cell and it ensures that
the cell remains protected inside
movement of substances in and out of the
cell is governed by the plasma membrane
that means it is the plasma membrane who
decides what all substances can move
across it and in which direction now
these substances include gases as well
as water by the processes of diffusion
osmosis because the plasma membrane will
decide whether the concentration is
higher or lesser on which end so which
your object is allowed to move from
website to website so the plasma
membrane has to decide flexibility
enables cell to invert food and other
materials from surroundings so this is
another new function here that is the
plasma membrane is so flexible that it
allows a cell to engulf food and other
materials from surroundings let us look
at an example the a best example for
this is amoeba so this is my amoeba now
because of the flexibility of the plasma
membrane as I told you before also the
amoeba does not have a fixed shape so
the plasma membrane here changes itself
and accordingly the shape of amoeba also
changes so the plasma membrane of an
amoeba is extremely flexible right now
how this flexibility helps any back to
engulf food or to intake food look at
this example this is this and this
process of angle
in foon because with the flexibility of
the plasma membrane this process is
known as endocytosis so this is known as
endocytosis right so what happens in
this process let us suppose this is the
ameba and this is some this this blue
colored object is some food material let
us say now what happens this amoeba will
change shape in this fashion so when it
changes in this shape in this fashion
the food month will be lengthened inside
this gap now as soon as the food oil
enters inside the gap then even again
changes its shape in this fashion so
that is how it helps to compete for food
so here the food was outside now the
food is inside amoeba right so the
because of the flexibility of the plasma
membrane amoeba can intake whom and this
process is known as endocytosis right so
this was another very nice function of
the plasma membrane right okay so we
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