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Biology Y2 > 5.4: Nitrogen Cycle > Flashcards

5.4: Nitrogen Cycle Flashcards

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1
Q

Name 2 common elements recycled by microorganisms

A

nitrogen and phosphorus

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2
Q

name 2 biological molecules containing nitrogen

A

amino acids, nucleic acids

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3
Q

name 2 biological molecules containing phosphorus

A

phospholipid, ATP

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4
Q

Describe the role of saprobionts in decomposition

A

Saprobionts secrete digestive enzymes onto the DOM, these enzymes hydrolyse the biological molecules in the DOM. The soluble products of the hydrolysis can be absorbed back into the fungi hyphae. The inorganic/ammonium/phosphate ions remain in the soil available to plants. The saprobionts respire aerobically releasing carbon dioxide

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5
Q

What are the 4 processes of the Nitrogen Cycle

A

Nitrogen fixing, Ammonification, Nitrification, Denitrification

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6
Q

What are legumes

A

Nitrogen fixing plants

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7
Q

What type of bacteria carries out the process of nitrogen fixing

A

Nitrogen fixing bacteria

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8
Q

What nitrogen conversion occurs during the process of nitrogen fixing

A

Reduction
N2 -> NH3

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9
Q

What type of respiration do the bacteria do during the process of nitrogen fixing

A

aerobic

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10
Q

What type of bacteria carries out the process of ammonification

A

Saprobionts

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11
Q

What nitrogen conversion occurs during the process of ammonification

A

Amino Acids -> NH3

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12
Q

What type of respiration do the bacteria do during the process of ammonification

A

aerobic

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13
Q

What type of bacteria carries out the process of Nitrification

A

Nitrifying bacteria

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14
Q

What nitrogen conversion occurs during the process of nitrification

A

oxidation
NH3 -> NO2- -> NO3-

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15
Q

What type of respiration do the bacteria do during the process of nitrification

A

aerobic

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16
Q

What type of bacteria carries out the process of denitrification

A

denitrifying bacteria

17
Q

What nitrogen conversion occurs during the process of denitrification

A

reduction
NO3- -> N2

18
Q

What type of respiration do the bacteria do during the process of denitrification

A

anaerobic

19
Q

Nitrogen fixing bacteria do what do nitrogen?

A

reduce N2 to NH3 (ammonia)

20
Q

Saprobionts do what do amino acids?

A

convert it to ammonia

21
Q

nitrifying bacteria do what to ammonia?

A

oxidise ammonia to nitrite ions, and further oxidise that to nitrate ions

22
Q

denitrifying bacteria do what to nitrate ions?

A

reduce it to nitrogen

23
Q

How do legumes gain an advantage in N-poor soils

A

they outcompete other plants

24
Q

How are legumes at a disadvantage in N-rich soils

A

any other plant outcompetes legumes

25
Q

Explain how legumes carry out their process of nitrogen fixing

A

Rhizobium bacteria on the plant roots produce nodules which fix nitrogen in the atmosphere and convert it into ammonia

26
Q

Why do plants need nitrogen

A

for the synthesis of amino acids

27
Q

why is nitrogen in the atmosphere not directly available to plants

A

it has a triple bond making it a very stable molecule

28
Q

how could you identify plants growing in N-poor soils

A

stunted growth

29
Q

how does deforestation affect the nitrogen cycle

A

increase in soil erosion, increase in leaching of nitrates out of soil and so decrease in quality of soilho

30
Q

how does crop rotation improve soil fertility

A

increases it as nitrogen stays in the soil

31
Q

how does an increase in animal waste affect the nitrogen cycle

A

increase in DOM, increase in ammonification, increase in nitrates in soil

32
Q

what would happen if a farmer used too much fertiliser (N cycle)

A

excess nitrates leached out of soil into surrounding water bodies causing eutrophication

33
Q

Explain the symbiotic relationship between legumes and nitrogen fixing bacteria

A

legumes get N compounds
bacteria get C compounds

34
Q

How does harvesting of crops affect N cycle

A

decrease in N2 in soil

35
Q

Why is it necessary for farmers to plough their fields (N cycle)

A

to aerate the soil which decreases denitrification and increases nitrification

36
Q

Fully explain the nitrogen cycle

A

Atmospheric N2 -> nitrogen fixing bacteria -> proteins in plants -> DECOMPOSITION/ feeding -> proteins in animals -> DECOMPOSITION/excretion -> PROTEINS IN DOM/nitrogenous waste(urea) -> ammonification by saprobionts -> ammonia in soil -> nitrification -> nitrites in soil -> further nitrification -> nitrates in soil -> denitrification into atmospheric N2/absorption by plants

37
Q

Describe how an atom of nitrogen in a soil nitrate ion could become part of a protein molecule in a plant

A

nitrates absorbed into plant roots via active transport, these nitrates are used to synthesis amino acids, which are then used in translation of mRNA to a polypeptide chain to form proteins

Biology Y2 (7 decks)

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