The nitrogen cycle

Question 1

Where are biotic places nitrogen is found?

Answer 1

Plants, animals, decomposers, amino acids, proteins, nucleic acids, chlorophyll, phospholipids, ATP, NADP and NADPH

Question 2

Where are abiotic places nitrogen can be found?

Answer 2

Atmosphere, soil nitrites, soil nitrates, soil ammonia and urea

Question 3

What are the stages of the nitrogen cycle?

Answer 3

Assimilation, ammonifaction, nitrification, denitrification and nitrogen fixation

Question 4

What is assimilation?

Answer 4

Plants absorb nitrate ions from soil and convert these into organic molecules containing nitrogen (amino acids)

Question 5

What forms the source of nitrogen for animals?

Answer 5

Plant protein

Question 6

How are animal proteins formed?

Answer 6

Gut enzymes hydrolyse to amino acids which are rearranged

Question 7

What happens to excess amino acids?

Answer 7

They are lost in urine

Question 8

What is ammonification?

Answer 8

Dead plants, animals and faeces are converted to ammonia by soil decomposers

Question 9

What is ammonia a product of?

Answer 9

A waste product of saprophytic feeding

Question 10

What does ammonia form?

Answer 10

Ammonium ions in solution in soil water

Question 11

How can plant use ammonium ions?

Answer 11

As a nitrogen source

Question 12

What is the equation for the formation of ammonium ions?

Answer 12

NH3 -> NH4+

Question 13

What is nitrification?

Answer 13

Ammonium ions in well aerated soil are oxidised by soil bacteria and energy is released y the process for the bacteria

Question 14

What type of process is nitrification?

Answer 14

Anaerobic process

Question 15

What is an issue with nitrate ions?

Answer 15

They are easily washed out of soil into lakes or rivers

Question 16

What is the equation for the formation of nitrite ions?

Answer 16

NH4+ + O2 -> NO2- + O2

Question 17

What converts ammonium ions into nitrite ions?

Answer 17

Nitrosomonas

Question 18

What is the equation for the production of nitrate ions from nitrite ions?

Answer 18

NO2- + O2 -> NO3-

Question 19

What converts nitrite ions between nitrate ions?

Answer 19

Nitrococcus

Question 20

What can oxidise atmospheric nitrogen into nitrates?

Answer 20

Lightening

Question 21

What is the industrial process for nitrification?

Answer 21

The Haber-Bosch process

Question 22

What is denitrification?

Answer 22

When there is soil with high nitrogen content that becomes anaerobic, nitrates are removed from the soil by a series of reactions that strips the oxygen away, producing nitrogen gas

Question 23

What is the oxygen produced by nitrification used for?

Answer 23

Aerobic respiration

Question 24

How is denitrification prevented?

Answer 24

Improving soil drainage

Question 25

What are examples of soil bacteria?

Answer 25

Azotobacter and rhizobium

Question 26

What does azotobacter do?

Answer 26

It reduces nitrogen into ammonia

Question 27

Where is azotobacter found?

Answer 27

Free living in soil

Question 28

What does rhizobium do?

Answer 28

It forms symbiotic relationships with legumes (peas, clovers) and causes growth of root nodules, which is an example of mutualism

Question 29

Where is rhizobium found?

Answer 29

In roots

Question 30

How is rhizobium an example of mutualism?

Answer 30

The bacterium gains carbohydrate and energy from the plant ad plant gains ammonia source

Question 31

What type of process is nitrogen fixation?

Answer 31

Anaerobic

Question 32

What is the result of nitrogen fixation being anaerobic?

Answer 32

Need to keep oxygen levels in cells low

Question 33

What is the equation for the production of ammonia by rhizobium?

Answer 33

N2 + 6H+ +6e- -> NH4+