this is the nitrogen cycle universally hated questions can be quite complicated
this is really not as bad as most teachers make it out to be okay so I'm
going to start with a series of four boxes connected by arrows on the top
this is going to be the direction of flow pretty much and it should all make
a little bit more sense so let me draw the boxes first so far so good
these are squares are going to represent inorganic so if you don't know what that
means it means not containing carbon the inorganic forms of nitrogen that flows
through ecosystems I'm going to start here with the letter A easy to remember
the difficult thing often about these questions and exams is that they will
always give you a different diagram and it's always going to look slightly
different every textbooks going to represent it differently I would have
your version ie my version in your head crystal clear
you'll see there's not like this one and know what's what in terms of C sometimes
they're going to skip it sometimes they're going to change the
layout but if you are confident of what's wearing your head then you can
remap the question so that it makes sense to you and I always start here
with a so this is ammonium ions and ammonium ions as I said the direction of
flow is going to be in this direction ammonium ions are going to be
transformed into nitrite this is an eye and what I usually do is write this
underneath with a number one because it comes first because the next thing that
comes after this is pretty similar and you're gonna have to spell them
correctly because they are very easily confused as nitrate and usually I put in
here late so nitrate comes after nitrite we start with a at the beginning
alphabet nitrites nitrates and then the evil form that we do not
is nitrogen gas in the atmosphere so this is very unreactive in that it's
almost impossible for things to use I
might even put a little nasty cross in there because that's not what we want
that's not mr. Foreman action that biological things want nitrogen in okay
so what do we want nitrogen in well the easiest form of nitrogen to absorb the
plants are nitrates so plants are going to absorb these things so this is gonna
be plants and you need to know which kind of compounds contain nitrogen in
plants what any living thing is going to have nitrogen containing compounds in a
couple of fours I'm just going to put them in green so see if you can guess
what they are think test yourself they are proteins or
amino acids you can also have DNA or RNA so these is often the inference of the
question is about what do the biological ramifications of this mean in plants or
animals so I'm doing a circle around this circles are going to be organic
life forms and living things basically organic forms of nitrogen well these are
I'm going to put this arrow in black actually because this is not an arrow
that you need to know in terms of you're going to need to know the names of which
of these it all going to have a name in fact this one is just absorption not the
most important this one is going to be animals how do animals get their
nitrogen well they eat plants and where are the nitrogenous compounds in animals
well all living things I'm going to repeat this a lot of times protein and
DNA again animals are living they're going to go in a round circle okay so
what happens to the nitrogen compounds from animals and plants when they die or
maybe they excrete we just these things well they're going to be broken down by
decomposers or Sephirah by on source a probiotic bacteria microorganisms so
disaffected label for the stages afterwards so I'm going to call these
decomposes and I'm going to add a little note to
that fat probiotic micronus microbes where do they have their
nitrogenous compounds well you guessed it proteins and DNA and are they living
yes they are they go in a round bubble okay
so we're more or less done and then we need to conjoin the end of the cycle and
they're going to add a few other little bits and pieces as well but from here we
go back to ammonium and there's a few other bits and pieces but effectively
the cycle but we're most interested in is living things we want to do this as
much as possible or if when animal we want to do this as much as possible so
one of the names of these stages the names of these stages are this one we
are the process of making ammonia so this is ammonification specification the
process of making ammonia pretty straightforward
these two both have the same name these are nitrification and this one so this
not forgetting because it's the process of making sort of good nitrogen useful
nitrogen so nitrites and nitrates are soluble they can be absorbed by plants
and they can do useful fun stuff with them like to make proteins this stage
here we're converting it back into a form of nitrogen that we don't want the
nitrogen in the atmosphere and so we call this the nitrification we're
removing nitrogen from the biological system and the last stage that we need
to learn about during this stage almost two more I'm lying to you we're going to
we're going to go from nitrogen gas in the atmosphere straight into plants but
not everything can do this whenever we're taking nitrogen gas and converting
into a soluble form so apply something that a plant can use we're going to call
that nitrogen fixation
we're fixing it we're taking it from a useless form and putting it fixing it
into a good form now this is done generally speaking by bacteria in a meat
mystic relationship with Lake goo- plants so legumes is the French word
vegetables as an example of legumes are going to be pea plants lentils beans
things that vegetarians eat to get lots of protein why do they have lots protein
because they can do this they can take nitrogen out of the air they I have a
higher ratio of nitrogen in them so they have higher amount of proteins and this
is generally done by bacteria in the root nodules something else that I'm
going to put in here about denitrification the way that they tend
to ask this in exam questions this is nearly always under anaerobic conditions
and the way that question is usually asked is to do with how aerated the
soils or how waterlogged the soil is
that's how that question is usually asked and the last state that you need
to know about is called separable tick nutrition and well is it going to be a
key term this is digestion or decay of dead organic matter by extracellular
enzymes
okay so what is extra cellular enzymes or x-rays outside of the cell so these
these micro naeun's basically booze out their enzymes onto the substances the
enzymes catalyze reactions hydrolyze them break them down into simple
molecules which can then be absorbed through the membrane and this is how
they do their digestion so a quick summary remember you start with a you go
to nitrites because you could put an eye in it the second eye it can be a one
then it goes into nitrates this is nitrification making useful
nitrogen soluble it can be absorbed by plants where two plants animals and all
living things have their nitrogen in proteins and DNA basically this process
is evil denitrification it's removing nitrogen from the biological system it's
under anaerobic conditions and it's usually waterlogged soils there are a
magic group of bacteria that live in association with legumes legume plants
which can fix nitrogen nitrogen fixation and convert the nitrogen gas they
actually convert it into ammonium ions and then they do some fancy chemistry
but in terms of what you need to know its nitrogen fixation and it's done by
bacteria in association with legumes how does it get recycled back into ammonium
well superb antic nutrition is basically digestion and decay by extracellular
enzymes and this process is ammonification okay so we've done Arthur
Murray but there's one more thing that you need to know and as the names of the
bacteria which do a couple of these processes not all of them so here this
bacteria that does this is called nitrosomonas Lytro so you're just gonna
have to learn these but there is a little bit of a trick that we can use to
remember these so nitrosomonas has more letters in it than this one this is
nitrobacter
so we're going from long in to short and then this one here nitrogen fixation is
done by where am I going to squeeze him in it's going to be done by rhizobian so
rhizome or mycorrhizae is something you going to study probably as well a
rhizome means like root so these these live in the roots that's
a little bit of a clue in there and then the last stage that there's actually one
that I'm going to add on for you lucky extra people and it's another form
of nitrogen fixation and this one with nitrogen fixation because we're going
from nitrogen gas into ammonia nitrogen fixation is done by a Zota bacter these
are bacteria that live in the soil they do exactly the same as the Rhizobium but
they don't do it in association with leguminous plants
okay so that is the full detail there's not huge amount of writing on that page
I suggest you write this out as a skeleton so just the boxes and the
arrows no writing photocopy it I might even get somebody
to do that nicely and scan it and send it to me so then you guys can print it
out ten times it'll take you two minutes to fill that in once you get good at it
and you will not forget it and then again the key is just mapping the
diagram they give you in the exam - the one you've got clear in your head so
that you know what's happening each step of the way