Nitrogen Cycle

Question 1

Steps

Answer 1

-Nitrogen fixation
- Assimilation
- Ammonification
- Nitrification
- Denitrification

Question 2

Nitrogen fixation

Answer 2

atmospheric: N2 and O2 present in atmosphere converted to NO2 by lightning
biological: saprobionts convert N to NH3/nitrates in root nodules
- symbiotic relationship

Question 3

Assimilation

Answer 3

Plants absorb N2 containing substances through roots
- ions used to make amino acids, nucleic acids etc.
- eventually die and turn to organic matter

Question 4

Ammonification

Answer 4

• saprobionts break down organic matter
• firstly break down proteins using protease
• broken down further to remove amino acids groups
• saprobionts use products for respiration

Question 5

Nitrification

Answer 5

• nitrifying bacteria convert nitrates to nitrites and then N2 gas

Question 6

Denitrification

Answer 6

-NO3- ions are converted to N2 gas by denitrifying bacteria
- occurs in anaerobic, waterlogged soil