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GCSE Biology · key term
A soluble nitrogen compound that plants absorb from soil through their roots and use to make amino acids and proteins.
Used by Edexcel
Specification 9.15 · Paper 2
Revise: Nitrogen CycleMost of the nitrogen around them is nitrogen gas in the air, but plants cannot use this gas directly. Instead, their roots take up nitrogen-containing mineral ions, particularly nitrates, dissolved in soil water. The nitrogen cycle explains how nitrogen changes form and moves between the air, soil and living organisms, making nitrates available again after plants use them.
Distinguish nitrogen fixation from nitrification: fixation brings atmospheric nitrogen into the cycle; nitrification produces nitrates from ammonium compounds in soil.
Denitrifying bacteria remove nitrates from soil by converting them to nitrogen gas; they do not make nitrates available for plant uptake.
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