3.5.4 Nutrient Cycles Flashcards

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1
Q

How are nitrogen
compounds in animals made
available for plants? (8)

A
  1. Proteins/amino acids broken down;
  2. by saprophytes/decomposers;
  3. deamination/ammonium compounds/ammonia formed;
  4. Ammonia converted to nitrite;
  5. by nitrifying bacteria;
  6. Nitrite converted to nitrate;
  7. Nitrate can be absorbed by roots;
  8. Nitrogen fixation forms ammonium compounds;
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2
Q

Describe how the action of
microorganisms in the soil produces
a source of nitrates for crop plants.
(5)

A
  1. Protein / amino acids / DNA into ammonium compounds / ammonia;
  2. By saprobionts;
  3. Ammonium / ammonia into nitrite;
  4. Nitrite into nitrate;
  5. By nitrifying bacteria / microorganisms;
  6. Nitrogen to ammonia / ammonium;
  7. By nitrogen-fixing bacteria / microorganisms in soil;
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3
Q

Describe the phosphorus cycle. (10)

A
  1. Phosphate ions in rocks released to soil by erosion/weathering;
  2. Phosphate ions taken into plants by roots/root hair cells;
  3. Phosphate ions assimilated into DNA/RNA/phospholipids/NADP/RuBP;
  4. Rate of absorption increased by mycorrhizae;
  5. Phosphate ions transferred through food chain;
  6. Some phosphate ions lost by excretion/when plants and animals die;
  7. Phosphorus containing compounds are decomposed by saprobionts/fungi;
  8. Weathering of rocks releases phosphate ions into seas and taken up by aquatic producers/algae;
  9. Phosphate ions passed along food chain to birds;
  10. Guano returns phosphate ions to soils
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4
Q

Describe the importance of
phosphorylation
(2)

A
  1. Makes substrates more reactive;
  2. Lowers activation energy for the reaction
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5
Q

Describe
eutrophication (6)

A
  1. Growth of algae / algal bloom blocks light;
  2. Reduced / no photosynthesis so (submerged) plants die;
  3. Saprobiotic (microorganisms / bacteria);
  4. Aerobically respire / use oxygen in respiration;
  5. Less oxygen for fish / aerobic organisms to respire;
  6. (So) they die;
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6
Q

Describe the function of saprobionts
releasing carbon dioxide (6)

A
  1. Microorganisms are saprobionts/saprophytes;
  2. Secrete enzymes (onto dead tissue) / extracellular digestion;
  3. Absorb products of digestion/smaller molecules/named relevant substance;
  4. Synthesis of structural compounds/named compound;.
  5. Respiration provides energy for growth
  6. Respiration (by microorganisms) produces carbon dioxide;
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7
Q

Evaluate use of fertilisers for
mycorrhizas (4)

A

(Should not use fertilisers because)
1. Fertilisers prevent development of mycorrhizae;
2. Mycorrhizae help plants to take up nitrates/phosphates (causing an increase in crop yield);
(Should use fertilisers because)
3. Fertilisers containing phosphate and nitrate increase gross primary production so increase yield;
4. Most soil is poor in phosphate so without fertiliser so plant might not get enough phosphate;

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