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Biology A2 > Nitrogen Cycle > Flashcards

Nitrogen Cycle Flashcards

1
Q

What is the Nitrogen Cycle?

A

It shows hoe Nitrogen and its compounds are recycled in nature

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2
Q

Why is nitrogen important?

A

A vital element to all living things.

Nitrogen is used to compose: amino acids, proteins, nucleic acids (+ATP) and chlorophyll.

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3
Q

What form does Nitrogen need to be in for plants to take it up?

A

Ammonium Ion (NH4+) or Nitrate Ion (NO3-)

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4
Q

What are the four key processes in the nitrogen cycle?

A
  1. Nitrogen Fixation
  2. Ammonification
  3. Nitrification
  4. De-nitrification
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5
Q

Explain the process of Nitrogen Fixation

A

Nitrogen Fixation is the process that causes the strong two-atom nitrogen molecules found in the atmosphere to break apart so they can combine with other atoms

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6
Q

How does Nitrogen become fixed?

A
  1. Atmospheric Fixation - lightning
  2. Industrial Fixation (Haber Process)
  3. Biological Fixation
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7
Q

How does atmospheric fixation work?

A

The energy of lightning breaks nitrogen molecules apart and enables the nitrogen atoms to combine with oxygen forming nitrogen oxides.

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8
Q

How does industrial fixation work?

A

Under high pressure and temperature, with the use of a catalyst. Forms NH3 and NH4+

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9
Q

What is the free living Nitrogen Fixing Bacteria called?

A

Azotobacter

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10
Q

What is the symbiotic relationship Nitrogen Fixing Bacteria called?

A

Rhizobium

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11
Q

Describe the role and characteristics of Azotobacter bacteria

A

Highly specialized, living freely, ability to combine N with H to form ammonia or ammonium.

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12
Q

Describe the role and characteristic of Rhizobium bacteria

A

Symbiotic.
Trade NH4+ for sugars
Live in root nodules of legumes
Nitrogen in reduces to ammonium ion NH4+

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13
Q

What enzyme does Rhizobium use to fix nitrogen?

A

Nitrogenase

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14
Q

What is Ammonification / Putrefaction?

A

Decomposition by bacteria and fungi breaks down amino acids from dead animals and plants, faces, and urine and wastes into ammonia or ammonium ion.

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15
Q

What happens to ammonia or ammonium ion stored in the soil?

A

It is used in Nitrfication

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16
Q

What is Nitrification?

A

When ammonia/ ammonium ion is converted to nitrite ions

17
Q

What does Nitrosomonas convert?

A

Converts ammonia/ ammonium ion is converted to NITRITE ion

18
Q

What does Nitrobacter convert?

A

Nitrite ion is converted into a NITRATE ion (NO3-)

19
Q

Describe the Denitrification process

A

When Pseudomonas bacteria reduce nitrate ions back into nitrogen gas

20
Q

What is the roll of Pseudomonas bacteria?

A

To reduce nitrate ions into nitrogen gas

21
Q

What bacteria catalyses denitrification?

A

Pseudomonas

22
Q

How is atmospheric nitrogen converted into Ammonium (NH4+) and organic N containing molecules?

A

Nitrogen Fixation by Rhizobium and Azotobacter

23
Q

How is atmospheric nitrogen converted into nitrate (NO3-) in the soil?

A

Nitrogen Fixation

24
Q

How is Nitrate ion (NO3-) converted into atmospheric Nitrogen?

A

Denitrification

25
Q

How is Ammonium (NH4+) and organic N containing molecules converted into plant protein, DNA etc?

A

Nitrogen Fixation

26
Q

How does plant protein, DNA etc become Ammonia (NH3) in the soil?

A

Decomposition by Bacteria and Fungi

27
Q

How is Ammonia in the soil converted into a Nitrite ion (NO2-) in soil?

A

Nitrification by Nitrosomonas

28
Q

How is Nitrite ion (NO2-) in the soil converted into Nitrate ions (NO3-) in soil?

A

Nitrification by Nitrobacter

29
Q

How does man alter the Nitrogen cycle?

A

.Industrial production of inorganic fertilisers using the Haber process ( nitrogen fixation)
.Slurry production
.Eutrophication
.Ploughing turns soil over and increases the oxygen content of the soil
.Installing drainage systems reduces water logging allowing natural aeration of the soil
.Growing leguminous plants which have nitrogen fixing bacteria in root nodules increases the nitrate content of soil

30
Q

What causes Eutrophication?

A

When nitrates are washed into rivers, lakes and the sea.

31
Q

What causes algal bloom?

A

Nitrates in the water encourage rapid growth of algae

32
Q

Describe the Eutrophication process?

A

Excess of nitrates cause an algal bloom. Dense algal growth blocks out sunlight to oxygenating plants. When the plants and algae die they are broken down by aerobic bacteria using up the oxygen in water. As a result animals die, leading to lower biodiversity.

33
Q

What are three causes of Eutrophication ?

A
  1. Fertiliser or manure runoff from farmland
  2. Improper disposal of sewage
  3. Chemical and industrial waste
34
Q

What do fertilisers cause?

A

.Lack of biodiversity on land

Growth of grasses and nettles which outcompete wild flowers

Biology A2 (8 decks)

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