Nitrogen Cycle

Question 1

Nitrogen fixation

Answer 1

Nitrogen gas in the air is fixed by nitrogen fixing bacteria (free living or mutualistic)
It is converted to ammonia then ammonium ions

Question 2

Nitrification

Answer 2

Nitrifying bacteria covert ammonium ions to nitrite then nitrate in an oxidation reaction
(Taken in by plants through roots and used to make proteins, DNA etc.

Question 3

Ammonification

Answer 3

Saprobionts break down proteins in dead plants and animals (into amino acids then ammonium)
They release enzymes (extracellular digestion) to break down proteins, and then absorb the products by diffusion
This is called saprobiotic nutrition

Question 4

Denitrification

Answer 4

By anaerobic denitrifying bacteria

Concert nitrate to nitrogen gas

Question 5

Ploughing

Answer 5

Increases oxygen in the soil
Nitrifying bacteria, saprophytic bacteria and nitrogen fixing bacteria respire aerobically (use oxygen, releases carbon dioxide)

Question 6

Mycorrhizae

Answer 6

Help a plant to take up water and inorganic ions through the roots of the plant