✔️ The Nitrogen Cycle Explained | A-Level Biology Tutorial | AQA
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✔️ The Nitrogen Cycle Explained | A-Level Biology Tutorial | AQA


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

56 thoughts on “✔️ The Nitrogen Cycle Explained | A-Level Biology Tutorial | AQA

  1. Thank you so much, this video helped me out a lot. Just wanted to let you know that you make great videos and tutorials, and to be quite honest, you videos are underappreciated. Keep up the great work 🙂

  2. Immobilization? Might want to add this process from NO3 (Nitrate) to soil biota. Here is the doc I refer students to in lab: http://cceonondaga.org/resources/nitrogen-basics-the-nitrogen-cycle

  3. Well done! Very useful video! It would be even more useful if you put English subtitles or if you enabled other users to do them. Thank you for your work 🙂

  4. (When you didnt know that the nitrogen cycle existed)
    Huh… I thought the water cycle was hard in kindergarten…

  5. Hey if any one is doing May June next month hit me up if you pass this😅😅….. just wana see if I'm not the only one who finds this hard

  6. Subscribe to this channel with ONE-CLICK: https://www.youtube.com/channel/UCb1bDd6OobkGkv2L23oa44g?sub_confirmation=1
    View the full course at http://tailoredtutors.co.uk

  7. do we actually need to know the names of bacteria ?
    also is symbiotic relationship the same as mutualistic? and where would miccorhizae fit in ?
    Thank you

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