A2 Biology (OCR)- The Nitrogen Cycle

Just made a diagram (it's not completely clear, sorry, I didn't realise the writing would be so small :S) and a powerpoint explaining the different areas of the nitrogen cycle in all the depth you'll need to know for your A2 exam. :)

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The Nitrogen cycle…read more

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The importance of nitrogen
Nitrogen is a key component of the metabolism
of living creatures. It is needed to make proteins
and nucleic acids.
It is the most abundant gas on the planet, but it is
very unreactive, so plants cannot use it directly
as a gas. First, it must be `fixed', in the form of
Ammonium ions (NH4+) or Nitrogen ions (NO3+).…read more

Slide 4

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Fixation of Nitrogen
This can happen in a number of ways:
1. The Haber process
2. Lightning strikes (these 2 only account for
about 10% of lightning fixation)
3. Nitrogen fixing bacteria.…read more

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Nitrogen fixing bacteria
Many of these live freely in the soil, and fix N2
which is in the air in the soil, and use it to make
amino acids.
Some bacteria, such as Rhizobium, live in the
root nodules of leguminous plants (such as bean
and pea plants). They have a mutualistic
relationship with the plant: i.e. They give the
plant fixed nitrogen, and the plant gives them
glucose.…read more

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Animals and decomposition
The nitrogen that is available in plants gets
digested by primary consumers. These animals
eventually die, and the valuable nutrients and
fixed nitrogen still in their system is broken
down and digested by bacteria and fungi.…read more

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There are some scientific errors within this powerpoint:

  • Nitrogen gas is fixed into ammonium ions or NITRATE ions (NO3-)
  • In denitrification, nitrate ions are converted back into NITROGEN gas (not oxygen), and nitrous oxide

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