nitrogen cycle

Question 1

why is the nitrogen cycle important ?

Answer 1

• because the air is 78% nitrogen
• but plants and animals cannot obtain nitrogen through gas exchange

Question 2

what is the structure of nitrogen gas
(n2) ?

Answer 2

• contains a triple bond between the nitrogen atoms

Question 3

what is the role of microorganisms in the nitrogen cycle ?

Answer 3

• mircroorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb

Question 4

what is unique about the triple bond ?

Answer 4

• the triple bond is extremely strong
• so it is difficult to break the bond and causes nitrogen to be an inert gas

Question 5

how will plants and animals absorb the nitrogen containing substances ?

Answer 5

plants= active transport through the roots
animals = digestion and absorption of plant material

Question 6

which biological molecules contain nitrogen ?

Answer 6

• proteins and amino acids
• ATP (adenine is a nitrogenous base)
• nucleic acids (DNA and RNA)

Question 7

what are the 4 key processes in the nitrogen cycle ?

Answer 7

• ammonification
• nitrification
• nitrogen fixation
• denitrification

Question 8

the nitrogen cycle does not work without… ?

Answer 8

• saprobiotic nutrition and microbes

Question 9

where does nitrogen fixation occur ?

Answer 9

• in the soil
• wither in the naturally occurring fixating bacteria
• or the fixating bacteria in the nodules (legume) on roots of plants

Question 10

where does ammonification occur ?

Answer 10

by decomposers in the soil

Question 11

which process in the nitrogen cycle is not wanted in agriculture ?

Answer 11

• denitrification
• because ypur losing nitrogen and nitrogen containing compounds from the soil

Question 12

when will denitrification occur and why ?

Answer 12

• when there is not enough oxygen in the soil
• ## because the denitrifying bacteria respire anaerobically

Question 13

when can denitrification occur ?

Answer 13

• when there is low oxygen conc in the soil
• so when the soil is water clogged
• the oxygen has been displaced by water

Question 14

what do farmers do to maintain a high oxygen conc in the soil ?

Answer 14

• they plough the soil

Question 15

what kind of reaction is
ammonia –> nitrites —-> nitrates ? and why ?

Answer 15

-oxidation
- the nitrifying bacteria are aerobic bacteria so will only work in the presence of oxygen

Question 16

what is the nitrogen containing compound in animal waste products ?

Answer 16

• urea in urine

Question 17

what is the nitrogen containing compound in dead plant matter ?

Answer 17

• protein in dead plant matter

Question 18

what happens in nitrogen fixation ?

Answer 18

• nitrogen gas is converted into nitrogen containing compounds

Question 19

what kind of relationship is there between nitrogen fixing bacteria and the legumes? and why ?

Answer 19

• a symbiotic relationship
• because the bacteria get carbohydrates from the plants and the plants get amino acids from the bacteria

Question 20

what kind of decomposers convert animal and plant waste product and dead matter into ammonia ?

Answer 20

• saprobionts

Question 21

how can nitrates be absorbed into the plant ?

Answer 21

• by root hair cells through active transport