Nitrogen Cycle

Question 1

Why is nitrogen essential to life?

Answer 1

It makes up nitric acid, a monomer of DNA and RNA.

Question 2

What sphere are the following compounds in? Nitrogen gas (N2) and nitric oxide and nitrous oxide (NO and N2O)

Answer 2

Atmosphere

Question 3

How much of the atmosphere does nitrogen gas make up?

Answer 3

70%

Question 4

What sphere are the following compounds in? Ammonia (NH4), urea/organic nitrogen ((NH2)2CO) and nitrate (NO3)

Answer 4

Biosphere

Question 5

Which sphere are the following compounds in? Ammonia (NH4) and nitrate (NO3)

Answer 5

Lithosphere and hydrosphere

Question 6

What is nitric and nitrous oxide (NO and N2O) commonly known as?

Answer 6

Greenhouse gases and smog.

Question 7

Is nitrogen gas accessible by plants or animals?

Answer 7

Not accessible to MOST living organisms.

Question 8

Is ammonia accessible by plants or animals?

Answer 8

Yes

Question 9

Is urea/organic nitrogen accessible by plants or animals?

Answer 9

Yes

Question 10

Is nitrate accessible by plants or animals?

Answer 10

Yes

Question 11

Is nitric and nitrous oxide accessible by plants or animals?

Answer 11

No

Question 12

What is the process of nitrogen fixation in the nitrogen cycle?

Answer 12

Bacteria called nitrogen fixing bacteria can take nitrogen gas from the atmosphere and convert it to ammonia. The bacteria live in the soil or in a symbiotic relationship with the root nodules of legumes (peas, lupin etc). In the hydrosphere cyanobacteria (blue-green algae) can fix nitrogen. These bacteria contain enzymes that can break the bonds between the two nitrogen atoms so they can bond with other elements. Lightning also has enough energy to break apart these bonds so is able to fix nitrogen.

Question 13

What nitrogen compounds are involved in nitrogen fixation?

Answer 13

Nitrogen gas and ammonia.

Question 14

What organisms are involved in the process of nitrogen fixation?

Answer 14

Nitrogen fixing bacteria

Question 15

What is the process of nitrogen uptake in the nitrogen cycle?

Answer 15

Plants are able to uptake ammonia.

Question 16

What organisms are involved in nitrogen uptake?

Answer 16

Plants

Question 17

What nitrogen compounds are involved in nitrogen uptake?

Answer 17

Ammonia

Question 18

What is the process of feeding in the nitrogen cycle?

Answer 18

Animals eat the plants that have uptake ammonia, the animals convert ammonia to urea which is excreted in urine.

Question 19

What organisms are involved in feeding?

Answer 19

Plants and animals

Question 20

What nitrogen compounds are involved in feeding.

Answer 20

Ammonia and organic nitrogen.

Question 21

What is the process of decomposition in the nitrogen cycle?

Answer 21

When organisms die, decomposers consume the organic matter and lead to the process of decomposition. During this process, the nitrogen contained within the dead organism is converted to ammonium (ammonification).

Question 22

What organisms are involved in decomposition?

Answer 22

Bacteria and fungi

Question 23

What nitrogen compounds are involved in decomposition?

Answer 23

Organic nitrogen and ammonia

Question 24

What is the process of nitrification in the nitrogen cycle?

Answer 24

Nitrifying bacteria are able to convert ammonia in the soil to nitrate in the presences of oxygen.

Question 25

What organisms are involved in nitrification?

Answer 25

Nitrifying bacteria

Question 26

What nitrogen compounds are involved in nitrification?

Answer 26

Ammonia and nitrates

Question 27

What is the process of denitrification in the nitrogen cycle?

Answer 27

Denitrifying bacteria convert nitrates back to atmospheric nitrogen in anoxic (no oxygen) conditions such as in waterlogged soils.

Question 28

What organisms are involved in denitrification?

Answer 28

Denitrifying bacteria.

Question 29

What nitrogen compounds are involved in denitrification?

Answer 29

Nitrates and atmospheric nitrogen.

Question 30

Draw an annotated diagram of the nitrogen cycle. (6 marks)

Answer 30

Half a mark for each correct process described.
Full marks if all processes above are included and described.

Question 31

What are some of the reasons that organisms need nitrogen?

Answer 31

• Proteins- makes up nucleotides
• Nucleic acids

Question 32

What do the bacteria that live in legumes do?

Answer 32

Break down the nitrogen and convert it to ammonia.

Question 33

What can over fertilising crops do to the nitrogen cycle?

Answer 33

Excess nitrogen from the fertilisation of plants can run into waterways, this causes an increase in algae. When algae dies it can cause eutrophication to occur. The dissolved oxygen used in the decomposition of the dead algae can be used up in the water, leaving other organisms with none.