Nitrogen Cycle

Question 1

1) Explain what Nitrogen Fixation is

Answer 1

• Some soil bacteria can convert nitrogen (N2) into nitrogen compounds
• These bacterium are called nitrogen-fixing bacteria
• They have a mutualistic symbiosis with legumes (eg: peas)

Question 2

2) Explain the process of ammonification and decomposition

Answer 2

• Organic material dies
• Bacteria and fungi (decomposers) use extra cellular enzymes to break down large complex molecules (eg: proteins, nucleic acid) into smaller ones
• This is known as DECAY
• Nitrogen found in proteins can be broken down into ammonium (ammonification)

Question 3

3) Explain the process of nitrification

Answer 3

• Nitrifying bacteria are found in aerated soil
• Ammonia and ammonium are diverted into nitrite (NO2-) by aerobic nitrifying bacteria
• The addition of oxygen by aerobic nitrifying bacteria produces nitrates (NO3-), which can be easily absorbed by plant root hair cells

Question 4

4) Explain the process of Denitrification

Answer 4

• Nitrates in the soil can be converted back into nitrogen gas by Pseudomonas Bacteria under anaerobic conditions
• These bacteria thrive under waterlogged and compacted soil, making it have little nitrate but lots of nitrogen gas released

Question 5

What is the use of nitrates?

Answer 5

Provide nitrogen to plants to make amino acids (the building blocks of proteins)

Question 6

True or False:

Nitrogen isn’t found in the organic based making up DNA AND RNA

Answer 6

False

It is found in DNA and RNA

Question 7

List 3 things in which nitrates can be found

Answer 7

• Inorganic fertilisers - made using the Haber Process
• Organic Fertilisers- when manure releases ammonia, is oxides and eventually releases nitrates
• Growing legumes - which contain nitrogen fixing bacteria in their root nodules