Electron transport chain : NADH, FADH2 - Respiration in plants, Biology, Class 11 Video Lecture

hello friends this video on respiration
in plants part 13 is brought to you by
exam for your calm no more fear from
exam so now we will first talk about the
NADH pathway so if one pathway is clear
to you then it will be easy to
understand the other pathway also so let
us look at the NADH pathway so let's see
what happens so when we are talking
about NADH pathway our starting material
is going to be NADH 2 so here we will
see how the energy in nadh 2 is utilized
to synthesize ATP ok so what happens
here is NADH produced during Krebs cycle
that was produced when I say during
Krebs cycle event I mean all the steps
till kreb cycle so whatever event H is
produce till now it binds to complex one
so where is my complex one this is
complex one so it is binding to the
first complex ok now electrons are
transferred to coenzyme q that does
ubiquinone which is present between
complex one and complex 3 so here you
can see ubiquinone so this electron will
get transferred to this and this is a
mobile carrier so it will carry the
electron to complex 3 so the electrons
will be transferred to complex 3 so from
there it will be picked up by cytochrome
C which is present on the outer side of
the membrane
and sin now this cytochrome C is again a
mobile carrier and it will transfer the
electron too complex for so now that
electrons have reached complex for now
one simple question that might have
struck your mind from where are these
electrons coming now's the simple answer
is the electrons are coming from NADH to
so when the NADH 2 is broken it breaks
into nad plus and h plus R a it forms
nad plus and h plus so basically each
NADH 2 molecule will give two electrons
and one hydrogen ion or proton to the it
will really is these two things now when
it releases all these things the
hydrogen ion will move out as you can
see here the hydrogen out iron will move
out of this membrane so if this is your
email membrane this space is the inter
membrane space so hydrogen ions are
moving out to the inter membrane space
but the two electrons are getting
carried over to this chain so the
electrons are basically coming from NADH
to now NADH to being a high-energy
molecule the electrons which are coming
are also high-energy electrons and that
is why it is moving down the potential
plane hit because it wants to attain
lesser energy and more stability so
finally the electrons are transferred to
complex for now what happens oxygen is
present here and this oxygen is the
final electron acceptor so till now none
of the complexes were actually absorbing
the electrons they were just passing on
the electrons to the next complex but
now oxygen will bind with that electron
pair and with a proton which is present
in the matrix to form water so that is
how oxygen will form water and now you
do not have those electrons now if
oxygen would have not been there there
would have been nobody to accept this
electrons in that case there would have
been too many electrons getting
accumulated inside right and in that
case the proton gradient would have not
been created now here as this process
takes place what is happening the
electrons are getting transferred and
finally getting accepted by oxygen to
form water molecule at the same time
this hydrogen ions at each step because
every time an NADH is coming to bind
with complex one hydrogen ions are
pushed into the intermembrane space so
that is how the concentration of
hydrogen ions in the intermembrane space
is increasing there are too many
hydrogen ions in this region when
compared to the matrix so as a result a
potential gradient is so as a result of
this entire movement of electrons in the
NADH pathway what happens is a proton
gradient is developed that is the proton
concentration in the intermembrane space
increases as compared to the proton
concentration in the matrix and due to
this development of proton gradient ATP
synthesis takes place now any the
synthesis H is that we will see a little
later so here let us quickly review the
process how proton gradient develops
first these two electrons are
transferred from NADH to complex one now
as these electrons are transferred
coupled with this as the pumping of
hydrogen ions from the matrix to the
intermembrane space so as soon as the
electrons are transferred to complex one
hydrogen ions are also pumped into the
intermembrane space now these two
electrons are then transferred through
points and few to complex 3 then you
cytochrome C and finally to complex for
their after those electrons are taken in
by the oxygen to form water now due to
the accumulation of hydrogen ions in the
intermembrane space a proton gradient is
developed and this proton gradient
is responsible for the synthesis of ATP
so this is about the NADH pathway in a
similar way fadh2 pathway also works the
only difference is in the starting point
so here what happens is there is no role
of complex one so complex one is not at
all involved here so here complex two is
involved so if you see fadh2 is produced
during the thread cycle right so here
from the Krebs cycle
fadh2 is produced and then it is passed
on to this complex two so if you look at
the step 6 of the Krebs cycle you can
actually see context - on x2 is present
in the step 6 of Krebs cycle that is
succinate dehydrogenase so that is your
complex 2 so from here it passes on to
the coenzyme q and then the same process
follows from coenzyme q it moves on to
complex 3 from Bach X 3 it is padded to
cytochrome C from cytochrome C it moves
on to complex 4 so in that process
remains the same just that in case of
NADH pathway complex 1 is involved in
case of fadh2 pathway complex 2 is
involved so he again once the electrons
reach complex code the same thing will
happen oxygen will come into picture it
will combine with the electron pair to
form water molecule and as a result of
this process hydrogen ions will get
accumulated in the intermembrane space
and as a result a proton gradient will
be developed so please understand how
proton gradient is getting them done
because that is the most important part
here so once the photon proton gradient
is developed after that the ATP
synthesis process is simple because in
our previous lesson when we were talking
about photosynthesis we spoke about the
chemiosmotic hypothesis so we used on
that kami osmotic hypo
only ATP gets synthesized so the proton
gradient development when I see a proton
gradient is developed what I mean is
this is the membrane which I am talking
about right so outside this membrane
that is in this inter membrane space the
concentration of the protons increases
so too many protons get accumulated here
and as a result the concentration is
very high in this space and the
concentration is quite low in this space
so because of this proton gradient ATP
synthesis will take place by
chemiosmotic hypothesis now let us
quickly see what is thank you please
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