Edexcel IGCSE Biology · Spec 4.11B
The Nitrogen Cycle
The nitrogen cycle and the roles of the different types of bacteria within it.
Biology revision video
The Nitrogen Cycle
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Spec 4.11B
What you need to know
- Explain why organisms need nitrogen
- Explain the roles of microorganisms in the cycle
- Describe the complete nitrogen cycle
Active recall
Quick check
Answer each question before opening the answer.
What do nitrogen-fixing and denitrifying bacteria do?
Nitrogen-fixing bacteria convert nitrogen gas into nitrogen compounds/nitrates; denitrifying bacteria convert nitrates back into nitrogen gas.
What is the role of decomposers in the nitrogen cycle?
They break down proteins and urea, releasing ammonium compounds (which nitrifying bacteria turn into nitrates).
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