Interphase: G1, S, G2 phase- cell cycle and cell division, Biology, Class 11 Video Lecture

hello friends this video on cell cycle
and cell division part 5 is brought to
you by example calm no more fear from
exam so what is interphase as I said
this is that phase during which the cell
prepares itself so that it can divide
later so this interface is as already
distance divided into 3 parts that is g1
s and g2 so these 3 stages together
comprise the interphase stage now in
this stage we have cells like this this
is one cell and this is another cell so
you have separate cells individual cells
which get matured prepares itself for
the cell division now we will discuss
about this phase in detail so this is
also known as the resting phase resting
phase in the sense that the cell is not
dividing so it is taking rest so that
where the dividing stage comes it can be
active to divide so it is divided into
three phases g1 that is gap 1 or first
graph phase s that the synthesis phase
and g2 that is gap 2 or second gap phase
so let us talk about g1 that is first
gap please so as it says gap that means
it is a break like when work really hard
you need a break in between so that
means this is also a break phase or a
gap phase so this phase in this phase
the same is metabolically active when I
say metabolically active what do I mean
I mean to see that the cell is active to
carry out metabolism metabolic samar all
the life process is taking place inside
our body we have talked about metabolism
in our previous lesson right all the
different type of chemical reactions
taking place inside our body for
respiration digestion excretion they all
fall under metabolic reaction and all
these things together which help in
sustaining life is known as metabolic so
in this stage
is metabolically active so all the
processes are taking place inside the
cell and the cell in continues to grow
so this phase occurs prior to
duplication of DNA now the cell has to
grow at least to some extent so that it
can duplicate its DNA or it can copy its
DNA so this is how it looks like let us
suppose if this is the cell we have a
nuclear membrane because now we are
talking about eukaryotic cell so here
this dotted structure which you say see
that is nothing but that nuclear
membrane this structure which you see at
the centre that is nothing but nucleolus
and these thread-like structures which
you see they are nothing but the
chromatin threads and these chromatin
threads will little condensed to form
the chromosomes we are all familiar with
these terms by now if not please let for
the lesson on cell so that you get to
know about each part of the cell in
detail so now right now the cell is
metabolically active and it is growing
so the cell grows and reaches maturity
now as well this phase comes this is the
first step as well as if you see it
comes after the last step of the cell
cycle what is the last step of the cell
cycle that is cytokinesis that is the
cytoplasm divides and daughter cells are
formed now the daughter cells are
nothing but the newly formed cells the
newly formed cells immediately cannot
divide any they need to grow they need
to make sure so this is the stage where
they grow and mature in order to grow or
mature what has to happen so many
metabolic activities need to take place
so these metabolic activities happens
here now during this phase the cell also
increases in Mass in preparation for
cell division because the is a simple
logic suppose if you if a small boy
wants to fight with a big boy he needs
to have lot of energy so in order to get
that energy what he tries to really
tries to eat well drink
so that he you regained some weight he
has some energy to fight similarly here
the cell needs to increase its mass to
prepare itself for the sent division so
this is g1 phase or the first gap fields
so here the cell does nothing no cell
division method ensures that all
metabolic reactions will take place
inside the cell and the cell will
gradually become mature so that all the
cell organelles are there in the cells
and the cell can go ahead now the next
phase that is the S phase which is also
known as synthesis phase synthesis means
to manufacture something to prepare
something now this is a very important
phase because it is in this phase that
DNA synthesis take is and you know how
important DNA is dealing is nothing but
the genetic material now if we want cell
to divide then the cell should have
multiple copies of DNA so that each of
them can be distributed to each daughter
cell very true right so that's the same
thing that copying of DNA or duplication
of DNA takes place in the synthesis
cells synthesis phase so this is how the
cell looks like again as I mentioned
before
so here DNA replication take place so
where is DNA in this cell can you tell
me you all know that ok so inside the
nucleus you have these thread-like
structures so these are nothing but the
chromatin threads and the chromatin
threads later become chromosomes and DNA
is present inside the chromosome so the
structure of the chromosome if you have
forgotten it loops upward like this and
you have genes arranged like this
correct so this gene has nothing but DNA
so DNA is present here so DNA
replication take place so that so here
you see they replicated DNA shown by
blue colored thread like structures now
to the D the process of DNA hopping
begins here now if in most of the cells
there is a narrow window of time during
which DNA synthesis occurs so this step
is not a very office lot of very long
duration it
short time and in that short time the
DNA quickly gets replicated so it is not
only the DNA replication which is
important it is also important that some
other important parts which participate
in cell division should also be
correctly hate it and one such part is
the centrioles Center your small
structures which are present within the
centrosome the centrioles occur in pairs
so these centrioles also duplicate so
you get one more pair of centrioles why
because see when you want the cell to
divide into two if this cell gets
divided to two you need to give the
genetic material to both of them you
need to give the centrioles to both of
them
now while sensual skidoo placated is
also because sensuous play a very
important role in the process of mitosis
and meiosis
so that is why also they need to be
raped duplicated we will see what role
it plays there so the sentence also get
duplicated now it is now to see that if
a cell is not a large enough for you if
it is not healthy enough in that is the
cell cycle stops here to prevent further
injury because let us suppose if the DNA
is not being replicated properly then
that is a problem because the correct
dear exact copy of the DNA should be
formed now if the cell is not healthy
enough to do that replication or if the
environmental conditions are not good
enough to make that replication possible
in that case the cell cycle will stop at
the S phase it will not proceed to the
next phase that is it will not proceed
to the g2 phase because if the DNA
replication is not proper even if you
forcefully make it move to do two phase
and it is off it is not going to be of
any use because you don't have all the
things that are needed for the same to
split into two house so it is very very
important that DNA duplication happens
in a very correct
now in order to check whether the G DNA
duplication happened in the right way or
not we have the next space that is
called a g2 phase or the second gap
phase here what happens is the beam is
checked by enzymes for mistakes and then
repaired as I said since DNA is getting
copied now it all happens that suppose
you miss your school for one day so what
do you do you miss the roads which your
teacher gave so what do you do you take
your friend's notebook and then you
start copying whatever was whatever
notes was given by a teacher now there
is a possibility that during comping the
notes you might make some mistakes and
copy now if you make some mistakes and
copying that is going to harm you that
is going to affect you because you are
walking into the wrong way so now the
same thing might happen here when the
DNA is getting copied there might be
some mistakes in the process of copying
so somebody needs to check if the
copying has been done correctly because
if this is the when when the cell
division actually takes place one
daughter cell will carry one DNA so the
daughter cell we get the copy DNA might
not function in the right way if that
copy DNA is not exactly the same as the
original DNA that is why it is very
important to test if the DNA has been
copied correctly therefore this step has
to come after synthesis phase because in
the synthesis phase the DNA is copied so
only after that you can check if it was
copied correctly or not so this is how
the DNA gets copy
let us suppose if this is your original
DNA and this is the copy DNA so you have
to make sure that the sequence of them
nucleotides here is exactly the same for
example I will give you a small example
it is suppose this is your original DNA
and this is the copy DNA so and
originality and if you see it both of
them looks like almost the same but not
exactly the same if you see here this
ocean has this but here you do not have
this so these kind of small changes mind
to be there and that is what needs to be
in this piece so that is the purpose of
this field now when you talk about the
gap phases whether it is g1 or g2 these
phases are less dramatic when compared
to the synthesis phase or the mitotic
phase which we will talk later now of
course it is very obvious that the
mitotic phase is going to be very
dramatic because the actual process of
cell division will take place there so
obviously that is going to be very
dramatic a lot of drama will happen a
lot of new cells will be formed
similarly the synthesis phase also if
you see DNA or being database which is a
very important step actual replication
is happening that is a gear also a
dramatic phase but if you see g1 nothing
as such happens it is just the normal
metabolic activities which keep on
happening inside the same similarly if
you look at g2 again here nothing
special happens it is just that the copy
DNA is just checked so anything new is
forming or nothing new is happening so
these two things is there and that is
why they are known as gap phases because
they are kind of break or they are kind
of resting phase however this is a very
important things because this series of
chains need to be performed to see if
the cell is actually ready for the cell
division so in this phase protein
synthesis also takes place because
proteins are something as you all know
the importance of proteins by now after
we have studied biomolecules so proteins
are needed for every activity that
happens in a cell so when you are going
to start and something like any division
you should have enough proteins
synthesized inside so that preparation
or for probe protein synthesis also
takes place in this g2 phase now when
you compare all these three phases of
the interphase it is seen that in most
of the cells G 1 that is the first gap
phase is the longest time of the cell
cycle so G 1 is the phase in which the
cells spend most of its time of its
entire life and that is the time which
is spent in undergoing the metabolic
activity growing and get
matured so that is the phase when the
cell spends most of its time so I hope
the concept of interphase is clear so
the cell is now getting prepared
so first what to do it will just grow
and mature can just undergo all the
metabolic activities that is g1 next to
synthesis where which is very very
important where it will copy or
replicate its duplicate its DNA so that
it can give one copy to each daughter
cell and the third phase is g2 where the
DNA is checked so that it has been
correctly copied or not and also
proteins and pencils will take things on
the set so that the cell is all set for
the same dilution to take place so now
if you if you want to quickly review how
protein synthesis used to take place you
can just have a look at this this was
the DNA which contained with stored the
genetic information so this DNA was
started by M RNA that is the messenger
RNA where transcription took place and
this messenger RNA then took it out of
the nucleus and took it to the ribosome
where the genes but where the protein
synthesis and how proteins are
synthesized the sequence of the
nucleotides actually helped to build the
amino acids and those are minor acids
together form the proteins so that is
our protein synthesis used to take case
so in this phase also the cell growth
continues the cell still continues to
grow so that process happens at its own
field at its own pace 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