Welcome back to the third lecture of the third
week of bioenergetics of life processes.
So, in the last class we talked about the
structure of the chloroplast knight, told
you that where possibly chloroplast may have
parasitized the transition from anaerobic
to the aerobic world and possibly somewhere
out there, those organelle which were getting
extinct somewhere or other encapsulated themselves
in an surrounding and some way or other we
really do not know how that possibly have
happened, but that is what at least with the
intellectual ability of mankind we as a race
contemplate.
So, coming back to the structure of the chloroplast,
so this is what we what we talked about?
The chloroplast has 3 different kinds of membranes
the inner membranes.
So, if you look at it the inner membrane.
The outer membrane and the thylakoid membrane
and we talked about 3 different kind of spaces;
the space between the inner and the outer
membrane between this green and the yellow,
then you have a space the stroma, which is
the space and then you have the thylakoid
space which is between the thylakoid membrane
So, today let us let us resume our week 3;
lecture 3 and in sum total this is lecture
13.
So, if you look at the chloroplast, so chloroplast
acid; the thylakoid membrane contains the
look the energy transducing machinery.
So, it is out here the thylakoid membrane
which has the TM or thylakoid membrane.
This contains the energy transducing machine
machinery energy transducing machinery and
which is essentially these are the point which
light harvesting proteins 
light harvesting proteins, then you have the
reaction centers or x is the reaction centers
then you have electron transport chain electron
transport chains and you have ATP Synthase.
So, now if I have to put it together, so this
is where light harvesting we talked about,
this is where how this is translated into
the reaction center and this is where the
whole flow of electron is happening and then
the synthesis ATP Synthase.
So, which is and this is governed by again
there chemi osmotic hypothcsis.
So, if you look back where we started the
show for this week.
We talked about the photosynthesis talked
about the chloroplast and the generation of
energy rich molecule out here, which is now
let us fit in ATP Synthase 
governed by chemi osmotic hypothcsis and another
system which is mitochondria which is non
light dependent and it does it in a different
way and we will talk about it.
So, this is when in the global scheme of things
false.
So, that is why I did not introduce slowly
I wanted to come and now 80 percentage when
you talk about in the chloroplast it is in
that thylakoid membrane where it is located.
So, it is in the thylakoid membrane where
ATP Synthase is present ok.
So, and if you really look at the chloroplast
they have nearly equal amount of lipids and
protein and the lipid composition is highly
distinctive, about 40 percent of the total
lipids are galacto lipids and 4 percent are
sulpho lipids and what are the significance
we really do not know so very well and 10
percent are phospholipids and which has nearly
equal amount of almost equal amount of lipids
and proteins, that is what makes up the thylakoid
membrane and thylakoid membrane like the inner
mitochondrial membrane is impermeable to most
of the molecules.
So, if you look at this thylakoid membrane
this is very similar to the cell membrane
which is semi permeable.
So, if you go back to the first week lectures,
when we talked about like let me see if I
could really take you back there when I talked
about.
Making of the membrane template for complex
synthesis and self assembly of making these
kinds of membranes which are formed, so possibly
these membranes now this is where it was.
These kind of membranes have learnt to be
semi permeable or selectively permeable.
So, how they learn this is another very interesting
story ok, but this fundamental concept.
If you recollect when I told you that all
these membranes are semi permeable in nature
and they are asymmetric in nature, and now
I am adding 1 more thing; they are made up
of lipids and proteins and with some form
of carbohydrates.
So, now talking about thylakoid membrane,
now let us come back and again start where
we were.
So, it consists of equal amount of lipids
and proteins and the lipids are either galacto
lipids, salpho lipids and phospho lipids,
at different composition where you have 40
percent of the lipids are galactolipids , salpholipids
are around 4 percent and 10 percent are phosphor
lipids.
thylakoid membrane the inner mitochondria
marine is impermeable to most of the molecules
and iron; the outer membrane of the chloroplast
like that of mitochondria is highly permeable
to small molecules, which is we are talking
about this outer membrane is permeable to
small molecules and ions; the stroma contains
soluble enzymes; this is the stroma, this
is a region which contain all sorts of soluble;
and when we talk about soluble we are talking
about water soluble, soluble enzymes ok.
That utilized NADPH and that utilize the NADPH
and ATP synthesized by the thylakoid membrane.
So, what these enzymes are doing is that these
solubilized enzymes.
So, the stroma contains soluble enzymes that
utilize the NADPH and ATP at the stroma, the
soluble enzymes are utilizing this NADPH and
the ATP in order to convert the CO 2 into
sugar, this is where the conversion of CO
2 to sugar is happening which is the reduction
reaction and the chloroplasts contain it is
own DNA and it is own machinery for applicating
and expressing it.
However chloroplast like mitochondria are
autonomous are not autonomous they also contain
many protein encoded by the nuclear DNA.
So, somewhere or at some point or other after
getting parasitized these organelle chloroplast
or mitochondria.
So, this is again other organelle what we
will be dealing with about I mentioned once
again mitochondria, these 2 are believed to
have parasitized the 
bigger or some other cell.
So, now though they have their own DNA or
own genetic material, both mitochondria and
the chloroplasts ; it is once again this is
empty DNA which is the mitochondrial DNA and
chl DNA is the chloroplast DNA though they
have their own DNA, but interestingly and
the code they code us and it is that their
DNA which is responsible for the replications
and everything, all their division is carried
out by their own DNA.
Yet they are not 
competent enough to have a autonomous existence,
they cannot survive independently that is
the cost they have paid by parasitizing themselves
into another host.
So, they lost their ability to have an independent
existence unlike possibly they used to have
at some point in distant past ok.
So, now having said this about the chloroplast
now let us move on to the basic reactions
of discovery of the basic reactions of photosynthesis
ok.
Discovery of 
the basic reactions of photosynthesis, so
if you look at most of the basic equations
of photosynthesis could have been written
at the end of 18th century, the production
of oxygen in photosynthesis was discovered
in 780 by Joseph Priestley.
So, Joseph Priestley basically he found that
the plants could restore air which has not
been injured by the burning of candles, basically
a simple experiment they did that whatever
is coming out from the plant and he basically
could help the life to survive ok.
So, Priestle has this classic experiment where
you have say for example, you have a plant
in a chamber where you have a green plant
growing and this is connected to 
that is bell jar where you have an animal
surviving ok
So, essentially the plant is giving every
oxygen and this oxygen is helping this animal
to survive, now if you burn this so basically
he found that the plants could restore here,
which has been injured by the burning of candles
he placed a sprig of mint in an invert inverted
glass jar in a vessel of water and found several
days later that, the air wound either extinguish
a candle nor was it all inconvenient to a
mouse which was put there ok.
So, similarly you can in a burn a candle out
there and it would not get extinguished.
So, this was the first discovery in the photosynthesis
that oxygen is evolved in photosynthesis,
now going by going back to that deceptively
simple reaction where it all started.
In the light of this if you look at this reaction
everything will make sense that oxygen evolution
ok.
So, this was the first of the very foremost
discovery of photosynthesis the evolution
of oxygen ok.
The next major contribution to the elucidation
of photosynthesis was made by Jean Ingen House
who was a Dutchman.
So, basically based on Priestley experiment
he went further and what it did is that he
figured out.
So, according to his own language he discovered
that the role of light in photosynthesis.
So, basically the person who discovered that
for synthesis can only happen in the presence
of light.
So, this was Jean Ingen House discovery that
it is not only that it is producing oxygen
for this process to happen you need light.
So, this was the second distinct contribution
and followed by that there was another guy
called Jean Seng Bier his distinctive contribution
was to show that the fixed air namely CO2
is taken up in photosynthesis.
So, basically the third name which comes into
play is Jean Seng Bier, who showed that CO2
is used in the process of a carbon dioxide
fixation or in photosynthesis.
So, now we have dealt with 3 different things,
so this gentleman showed the role of light
Priestley showed devolution of oxygen Jean
Seng Bier states, that it is the carbon dioxide
which is involved in it these are the 3 major
contribution which was made in the very early
between 1700 and 1800 centuries.
So, I will close in here in the next class
we will move on to the role of the chlorophyll
molecules ok.
Thank you.
