Nitrogen Cycle

Question 1

Why do living organisms require nitrogen

Answer 1

To manufacture :

• proteins
• nucleic acids
• other hydrogen containing compounds

Question 2

How do plants take up nitrogen

Answer 2

Take up nitrogen as nitrate ions from the soil by active transport

Question 3

1.) Ammonification

Answer 3

= production of ammonia from organic nitrogen containing compounds — urea, protein, nucleic acids, vitamins
Saprobiontic microorganisms feed on faeces real easing ammonia, leading to the formation of ammonium ions in the soil

Question 4

2.) Nitrification

Answer 4

= bacteria obtain their energy from chemical reactions involving inorganic ions

• Oxidative reaction of ammonium ions to nitrite ions which releases energy and the oxidation of nitrite ions to nitrarte ions
• oxygen is required for these reactions, so they require soil with many air spaces

Question 5

3.)Nitrogen fixation

Answer 5

• nitrogen gas converted into nitrogen containing compounds which can occur industrially or naturally when lighting passes through the atmosphere
  Carried out by : free-living nitrogen fixing bacteria, mutualistic nitrogen fixing bacteria

Question 6

Free living nitrogen fixing bacteria

Answer 6

• reduces gaseous nitrogen to ammonia this can then be used to manufacture amino acids
• nitrogen rich compounds are released from them when they die or decay

Question 7

Mutualistic nitrogen fixing bacteria

Answer 7

• live in nodules on the roots of plants
• they obtain carbohydrates from plants
• the plant acquires amino acids from bacteria

Question 8

4.) Denitrification

Answer 8

• when soil is waterlogged and has a low oxygen concentration, the type of microorganism present changes
• fewer aerobic nitrifying and nitrogen fixing bacteria, and an increase in anaerobic denitrifying bacteria
• these bacteria covert soil nitrates into gaseous nitrogen, this reduces the availability of nitrogen for plants