Nitrification & Denitrification Video Lecture | Biology for Grade 11

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with this we ended our discussion on
nitrogen fixation
so in nitrogen fixation we studied how
the atmospheric dinitrogen gas gets
converted into ammonia by different
means
biologically industrially and
atmospherically now we will talk about
another process of the nitrogen cycle
that is nitrification so what does
nitrification it is a process that
converts ammonia to nitrite and then to
nitrate so in the previous process that
is a nitrogen fixation B you saw that
atmospheric dinitrogen gas got converted
into ammonia so here the ammonia will
get further converted into nitrites and
nitrates
well the question is why do we need to
convert it into nitrites and nitrates so
we will see that very soon now this
process is also carried out by
prokaryotes when I say prokaryotes the
organisms without membrane bound
organelles mostly bacteria fall under
prokaryotes it is an aerobic process
that is it needs oxygen so now in the
previous process that is the nitrogen
fixation you saw that atmospheric
nitrogen gas got converted into ammonia
so this was nitrogen fixation right now
this ammonia will further get converted
into nitrites so this is nitrite and
this nitrite will further get converted
into nitrate so this process this entire
process is known as ninety vacation now
the question is why do we want to
convert them into nitrites and nitrates
that is because many plants I mean
basically I am
actually converting nitrogen because
this atmospheric nitrogen cannot be
utilized by plants or animals
now ammonia can be utilized by many of
them now nitrate is again a better form
or a usable form of nitrogen so there
are many plants which then utilize
nitrate now ammonia cannot be directly
converted into nitrate that is why
formation of nitrite is an intermediate
step so not the process of nitrification
consists of two steps step one where
ammonia gets converted to nitrite
step two by nitrite gets them go to to
nitrate so this entire process is known
as nitrification and it happens in
presence of oxygen
now this nitrite as I said can be
utilized by the plants this can be
utilized right okay now let us look at
the exact process what are the reactions
that take place in nitrification so the
first step as I said is oxidation of
ammonia to nitrite so what is ammonia
ammonia is nh3 and what is nitrate that
is no.2 hands so this is nitrite so what
happens in this step
this is ammonia ammonia gets oxidized
that is oxygen is added to it to form n
H 2o h plus h2o so on one step of
oxidation n h2o which that is hydroxyl
amine respond and water is raised
now this hydroxyl amine again from
nitrite and four electrons so conversion
of ammonia to nitrite in itself is a
two-step process
so if you see this is step one and this
is step two so what happens here the
microbes which are involved with the
microorganisms which
does this one conversion they are known
as ammonia oxidizers because they
oxidize ammonia they add oxygen to
ammonia so they are called ammonia
oxidizers intermediate products which
are formed as hydroxyl amine so hydroxyl
amine NH 2 O H is the intermediate
product which is formed so when I say
intermediate product I mean to say that
it if if there would have been only one
reaction where you started with ammonia
and you ended with nitrite in that case
there was no intermediate product but in
this case first you get hydroxyl amine
and then hydroxyl amine when again
hydrolyzed it gives nitrite so what are
the enzymes involved we have ammonia
modo oxygenase and hydroxyl amine oxido
reductase so for the first reaction the
enzyme which is involved is the first
enzyme this one II won so this is the
enzyme which is involved in the first
reaction where ammonia gets converted
into hydroxyl amine and the second
enzyme which is involved in the
oxidation and reduction of hydroxyl
amine that is this one hydroxyl amine
oxido reductase right so this is the
first step of nitrification in this
process small amount of energy is
generated not a veil Yuja mount of
energy so let us look at the step two in
step two nitrate will be oxidized to
form nitrate so what would be the
reaction here here no2 minus will be
oxidized to form no.3 minus some balance
the reaction so this would be your
reaction you start with nitrite just
oxidize it and you will get nitrate so
here the microbes which are involved or
which carry out this process are known
as nitrite oxidizing bacteria because of
their function because they actually act
oxidized nitrite and in the previous
step they used to oxidize ammonia so
they were quite ammonia oxidizers
if you talk about intermediate products
no intermediate products are form here
because it is a single step process
small amount of energy is generated so
in both
step step one and step two small energy
was generated so we can say that in the
entire process of nitrification a very
small amount of energy is generated so
that was all about nitrification let us
talk about the third process that is
denitrification so what does
denitrification the name itself is like
just the opposite of nitrification so
that was nitrification that is
denitrification and actually it is the
opposite process of nitrification so a
process that converts nitrate into
nitrogen gas so in the previous process
we converted ammonia to nitrate now we
are going to convert nitrate back to the
nitrogen gas and release it back to the
atmosphere so that is denitrification so
it returns nitrogen to atmosphere so in
nitrogen fixation we started from the
nitrogen gas present in atmosphere and
here we are giving back the same
nitrogen gas to the atmosphere so in the
first process that is nitrogen fixation
we saw that that was very nitrogen was
converted into ammonia by the process of
nitrogen fixation right then we saw that
this ammonia got converted to nitrate
and the nitrite got converted to nitrate
by a process called nitrification so now
in denitrification we will see that this
nitrite will get converted back into
atmospheric nitrogen so this process is
going to be denitrification so you see
now you can actually see that it is
forming a cycle it is forming a cycle
kind of a structure you started from
here and then you went through all these
and then you are coming back here it is
a cycle and this is how nitrogen cycle
is formed this process is also carried
out mostly by prokaryotes however some
you
it's also kind of this process it is an
anaerobic process so since it is just
the opposite process process of
nitrification so nitrification what did
we do we oxidized the ammonium that is
what we do so here we are not do that
we'll just do the opposite thing
so that is therefore it doesn't need
oxygen so it is an aerobic process so
let us look at so let us look at the
process so let us see what exactly is
the reaction that takes place during
this denitrification process so it
starts with nitrite and this nitrite
gets converted into nitrate the nitrate
gets converted into nitrate because
nitrite was the intermediate product by
form formation also during the process
of nitrification also nitrite was an
intermediate product so now when it is
going the reverse way then also nitrate
for first ones nitrite and from nitrite
nitrogen oxides are formed and this in
turn forms the nitrogen gas so here you
see a lot of intermediate products are
formed because gases are formed then I
oxide of nitrogen are formed so this is
the process of denitrification
so here the intermediate products are
gases like n 2 O and M o now another
important thing here is these gases
mostly this n 2 O this gas is considered
as a greenhouse gas what does the
greenhouse gas a gas which reacts with
ozone and contribute to the greenhouse
effect
so it causes air pollution so this gas
causes air pollution so that means this
process has some negative effects on the
environment so that means that is the
disadvantage of this denitrification
process so that is the disadvantage that
it contributes to air pollution however
there is an advantage also it plays a
very important role in the wastewater
management now you might ask why because
increased water they might have a lot of
nitrites and if
nitrates and if you have too much of
nitrates and water there are chances
that algal bloom might develop on that
water so in order to prevent that this
process removes unwanted nitrates from
the wings to water therefore it reduces
the chances of undesirable consequences
for example it reduces the chances of
algal blooms and on that so that means
it plays a very important role in
wastewater management thank you please
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