Nitrogen Cycle

Question 1

Nitrogen Fixing Bacteria

Answer 1

In the soil and roots of legume plants
Absorb nitrogen to make ammonia
Process called nitrogen fixation

Question 2

Nitrifying bacteria

Answer 2

Ammonia converted to nitrites and nitrates by nitrifying bacteria
Process: nitrification

Question 3

Plant roots

Answer 3

Can ONLY absorb nitrates
The nitrates combine with carbohydrates (from photosynthesis) to form amino acids
Amino acids made into proteins and nucleotides which are joined to make DNA and RNA

Question 4

Animals

Answer 4

Eat plants
Digest proteins and DNA
Absorb amino acids and nucleotides
Used to synthesise proteins and DNA (assimilation)

Question 5

Decomposing bacteria

Answer 5

Protein in dead plants and animals is broken down
Ammonia released into soil
Process called decomposition

Question 6

Denitrifying Bacteria

Answer 6

Process: Denitrification
Nitrates converted to nitrogen gas
Reduces amount of nitrate in the soil
Makes soil less fertile