Welcome back, to the lecture series on Bioenergetics
of Life Processes.
So, we have finished first 2 weeks and we
have talked little bit about or sufficient
enough of thermodynamics parameters; which
comes handy while we talk about, some of the
transformation of molecules and we have a
brief introduction about photosynthesis and
chemosynthesis.
So, today we are starting the 3rd week where,
these 2 weeks 3rd in the 4th week we will
be dealing with 4 different kind of energy
conversion processes where, thrust area will
be on the 4 topics what we will be dealing
with we will deal with photosynthesis the
light reaction and the dark reaction we will
deal with the process of generation of ATP
in the mitochondria the second energy harvesting
or energy utilization system and the governing
principle, which is dictating both this chloroplasts
and mitochondria is the chemiosmotic hypothesis
and the synthesis of ATP.
So, this all this process will go hand in
hand it is not that, will be standalone except
we will talk about the role of mitochondria
and role of chloroplast separately.
So, to start with our 3rd week and the first
lecture of a 3rd week as we have already talked
now, we are not talking about chemical synthesis
we are talking about photosynthesis light
dependent synthesis and in between we will
always have the comparative pictures of chemical
synthesis coming into play.
So, to start off with the perennial source
of energy is the sun.
So, we need it some way or other to trap the
sunlight and use that, solar energy to conduct
or do some useful work.
So, in nutshell if I had to put it photosynthesis
is a process where, the solar energy is being
used the energy of the photons is being is
being used to do some useful work using all
the natural ingredients.
So, the photosynthesis the raw material for
photosynthesis probably one of the most elegant
and one of the most genius move of nature
it uses carbon dioxide and water to start
off it’s photosynthetic machinery, but here
having said that, carbon dioxide in water
I must say the second component water this
component come much later into the play of
photosynthesis because, water as a matter
of fact act as a source of electron what does
that mean?
So, what essentially photosynthesis does in
nutshell if I if you have to see a photosynthesis,
photosynthesis is a process where, carbon
dioxide from nature is being taken up by plants
and it is converted into carbohydrates.
So, once CO2 is transforming into carbohydrate
you are adding a lot of hydrogen into it ok.
Now, that process of conversion of carbon
dioxide to carbohydrate is a reduction reaction.
In other word you are adding a lot of electron
into the carbon moiety.
So, that reduction reaction requires a supply
of electron from somewhere, which will govern
the system ok.
So, essentially in the process where, CO2
is getting self assemble to a much more larger
much more energy rich molecule, which is carbohydrate
requires an extra piece of energy, in that
in terms of it needs electron to make this
process happen and this electron source is
the first electron source in this game is
the water molecule.
But, if you replace water with another molecule,
which can be a source of electron you can
always conduct this process as a matter of
fact there where, times and even there is
situations where, even H2S can do that H2
H2S ok, it is the same thing as splitting
both the molecules.
So, let us start getting down all the points
what we are going to deal with.
So, this is our ok, So, this is our week 3,
lecture 1 and in overall this is lecture 11.
So, what we will be dealing with is this is
our perennial source of energy, which is involved
in photosynthesis ok.
Then we will talk about which happens in an
organelle called chloroplast organelle, which
is present inside the plant cells and it is
believed that, billions of years ago or maybe
millions of years ago this organelle parasitized
into the plant cell and become part of it
ok.
Then this is the first level of this is the
energy harvesting part, what we will be dealing
with 
energy harvesting 
next inside the cell, what we will be talking
about.
So, I am just putting it this 
double membranous structure what I am drawing
is the structure of the cell and here, you
have the structure of the chloroplast inside
the cell.
So, this is what we are talking about is the
cell and then, you have another organelle
which is close by to it, which is your mitochondria
ok, which is the powerhouse of the cell , powerhouse
of the cell and this process generates lot
of energy rich molecules in the form of ATP
and ADP, GTP the most critical one is the
ATP ok.
So, these are the 
generation of energy rich molecules 
in the form of GTP, ATP and ADP and critical
one is the ATP what we will be dealing with
and the interest ok.
So, the semi-permeable membrane of the cell
and this is governed by a hypothesis, which
was given by Peter Mitchell for ATP synthesis
it is called chemi osmotic hypothesis.
So, these are the 4 aspects what truly governs,
what we talk about the bioenergetics of life
tear the chloroplasts, tear the mitochondria
and this is your ATP generation and governing
dynamics is the chemi osmotic hypothesis and
earlier to that prior to that, was the world
of chemosynthesis, which still survive and
we will talk a little bit in between as we
will go through.
So, as will be going.
So, this is the overall framework what we
are going to deal in the next remaining classes
of the course or in the lectures is the chloroplast,
mitochondria, generation of ATP and the governing
dynamics a chemi osmotic hypothesis.
To start off with if we look at the reaction
of the photosynthesis just let me start out
here, if you see the reaction of photosynthesis
the reaction of photosynthesis is something
like this.
As I told you H2O plus CO2 a simple reaction
in presence of light making CH2O, which is
a carbohydrate plus oxygen this is your carbohydrate
and this is the byproduct, which is gas which
is the oxygen.
So, as some people say this is one of the
deceptively simple reaction as a matter of
fact it is funny that, nature is deceptively
simple it does things in such a simple way
that, it take mankind centuries to understand
what trick nature has done?
I mean if you look at it it is really straightforward
you have CO2 and you have another product,
which is fairly reduced now, the first question
which strike always strike in your mind, that
this oxygen which is liberated and it is strike
everybody all those who have worked in that,
area it always strike this oxygen is this
oxygen coming from carbon dioxide or is this
oxygen coming from water.
Because, if it is coming from water; that
means, if this is true if this situation is
true then, this is a situation where, water
is getting split splitting of water and if
water is getting a split if nature can split
water somewhere or other; that means, if we
could understand how nature split that water
then, from here one of the byproduct, which
mankind tries as a source of clean energy
is hydrogen see how everything is linked to
each other?
So, if some way or other while looking at
the simple reaction if somewhere or other
if this oxygen is being evolved by water,
that it means water is getting split some
way or other.
So, that brings us purple from bioenergy interested
in understanding people from chemistry, people
from physics, people from energy studies,
people from engineering, biology by engineers
they all are keen to understand as you move
through you realize, that is the oxygen which
is coming from water everybody is keen to
understand how nature does it?
And what do we know I am just giving you the
framework what we know nature does it in one
of the again deceptively simple way by something
called manganese cluster, which is part of
photosynthetic machinery.
To the best of our knowledge, what we know
about manganese cluster is it consists of
4 manganese iron sitting at different oxidation
state and somewhere, or other it can entrap
the water molecule in between it and could
you know like a zipper can split it up unzip
it 
and this hydrogen what is being liberated,
is that reducing force which essentially reduces
carbon dioxide to carbohydrate, that is what
I was trying to tell you?
So, if you look at the simplest reaction this
is essentially reduction of course, the assumption
that, oxygen is getting liberated from water.
So, though it is a deceptively simple reaction,
but this reaction has inspired generations
and it will inspire generations to explore
further understanding the whole thing at the
angstrom level and the challenge will be to
engineers structures engineer something like
manganese cluster, which can split water because,
if the day mankind can mimic this whole machinery
it can hit upon the food problem energy problem.
Look at that 2 things they need food and energy,
that is what govern our life these are the
2-important thing and if you look at this
reaction it actually generates both of them
food in terms of carbohydrate energy in terms
of so many reducing agent, which it is producing
which is.
So, that is why people have devoted their
life in understanding photosynthesis from
different perspectives from by an organic
perspective from biologists pers perspective,
from chemists perspective, from cyntha synthetic
inorganic chemist perspective, from engineers
perspective because, this deceptively simple
reaction makes all the difference.
Now, what is the role of light we have not
talked about, it there are 5 elements what
I have drawn here, 1 so water, 2 is carbon
dioxide, 3 is light, 4th is carbohydrate,
5th one as a byproduct, which is oxygen and
I told you that if you replace this H2S H2
with H2S then, to the same thing could happen
this may get split up and you still can produce
hydrogen, which could be used as a source
of energy as a source of very clean energy
ok.
So, with this background I will close in this
lecture and the next lecture we will go to
the next phase of it.
So, try to appreciate this simple reaction
what all could be done?
It is the dream, which is important for you
to appreciate that; this is how the whole
energetics rolls through.
Thank you.
