Nitrogen Cycle

Question 1

What is nitrogen?

Answer 1

Nitrogen (N) is present in biological molecules such as amino acids, proteins, and nucleic acids.

Question 2

What is Nitrogen present in?

Answer 2

In its inorganic form, nitrogen is present as nitrogen gas in the atmosphere (N2), ammonia (NH3), ammonium ions (NH,*), nitrates (NOz), and nitrites (NO2).

Question 3

What is Fungi - mycorrhizae?

Answer 3

Fungi - mycorrhizae facilitate the uptake of water and inorganic ions in plants.

Question 4

How many types of nitrifying - fixing bacteria is there?

Answer 4

Nitrogen-fixing bacteria - two types:
- ammonification by free-living bacteria in soil (e.g., Azotobacter)
- mutualistic with plants (e.g., Rhizobium is the bacteria associated with legumes)

Question 5

How is nitrifying bacteria reduced to ammonia?

Answer 5

• Nitrifying bacteria - oxidise ammonium ions to nitrites in the soil (e.g., Nitrosomonas) and nitrites to nitrates (e.g., Nitrobacter).

Question 6

How is denitrifying bacteria reduced to ammonia?

Answer 6

Denitrifying bacteria - anaerobically reduce nitrates and release nitrogen gas (e.g., Pseudomonas denitrificans).