Nitrogen cycle

Which biological compounds contain nitrogen?

• Proteins

• Amino acids

• DNA

• RNA

What is assimilation in the context of the nitrogen cycle?

It is the process by which plants use nitrates or ammonium ions they absorbed from the soil to create biological molecules like proteins. These molecules are then assimilated into the tissue of the plant.

What is the role of decomposers in the nitrogen cycle?

Decomposers produce ammonia from the nitrogen found in compounds like proteins.

Describe the process of nitrogen fixation.

Nitrogen fixation is the fixing of atmospheric nitrogen into ammonia via nitrogen fixing bacteria in legume root nodules.

They are then either assimilated by plants or converted into nitrates.

Describe the process of nitrification.

It converts ammonia into nitrites and then nitrates via nitrifying bacteria by oxidising the ammonia. (aerobic process) [farmers plough their soil to intorduce pockets of air for this]

They are then assimilated by plants and then the plants are consumed by animals, and nitrogen is passed along the food web.

What happens when plants and animals die?

When death and decomposition occurs, nitrogen is returned to the soil in the form of ammonia (ammonification).

The ammonia could stay in the soil or by converted back into nitrogen gas by denitrification.

Describe the process of denitrification.

It is the reduction of nitrates in the soil via denitrifying bacteria which occurs best in the absence of oxygen (anaerobic process).

What are the steps to complete a nitrogen cycle

1. Nitrogen fixation

2. Nitrification

3. Assimilation

4. Decomposition

5. Denitrification