Stages of the nitrogen cycle (19)

Question 1

What are the stages of the nitrogen cycle?

Answer 1

1. ingestion
2. digestion
3. assimilation
4. deamination
5. decomposition
6. nitrification
7. absorption
8. denitrification
9. nitrogen fixing

Question 2

ingestion

Answer 2

stage 1 - taking in of protein (food) into the body

Question 3

digestion

Answer 3

stage 2 - proteases break down protein into amino acids (trypsin and pepsin)

Question 4

assimilation

Answer 4

stage 3 - use by body cells of amino acids to make new proteins (new enzymes, hair protein, hormones)

Question 5

deamination

Answer 5

stage 4 - conversion of amino acids to urea for excretion (remove nitrogen)

Question 6

decomposition (decaying)

Answer 6

stage 5
- saprophytes cause decay
- decomposers: bacteria and fungi
- proteins decay to become ammonia gas
- ammonia then undergoes nitrification

Question 7

nitrification

Answer 7

stage 6 - conversion of ammonia into nitrate by nitrifying bacteria found in soil

• NH4 —–> nitrates

Question 8

detritus

Answer 8

waste (dead bodies)

Question 9

compost

Answer 9

plant waste manure

Question 10

absorption

Answer 10

stage 7 - absorption of nitrates by the roots via active transport
- nitrates are then converted to amino acids

Question 11

denitrification

Answer 11

stage 8 - conversion of nitrates in the soil to nitrogen gas via bacteria

reduce soil fertility (waterlogged soils) -> anaerobic conditions (lack of oxygen)

Question 12

nitrogen fixing

Answer 12

stage 9

nitrogen gas –> nitrates via nitrogen fixing bacteria

Question 13

symbiotic relationship between bacteria and plant

Answer 13

bacteria benefits as it is provided with glucose from the plant. plant uses bacteria too convert nitrogen gas to nitrates