3.5.4 Nutrient Cycles Flashcards
How are nitrogen
compounds in animals made
available for plants? (8)
- Proteins/amino acids broken down;
- by saprophytes/decomposers;
- deamination/ammonium compounds/ammonia formed;
- Ammonia converted to nitrite;
- by nitrifying bacteria;
- Nitrite converted to nitrate;
- Nitrate can be absorbed by roots;
- Nitrogen fixation forms ammonium compounds;
Describe how the action of
microorganisms in the soil produces
a source of nitrates for crop plants.
(5)
- Protein / amino acids / DNA into ammonium compounds / ammonia;
- By saprobionts;
- Ammonium / ammonia into nitrite;
- Nitrite into nitrate;
- By nitrifying bacteria / microorganisms;
- Nitrogen to ammonia / ammonium;
- By nitrogen-fixing bacteria / microorganisms in soil;
Describe the phosphorus cycle. (10)
- Phosphate ions in rocks released to soil by erosion/weathering;
- Phosphate ions taken into plants by roots/root hair cells;
- Phosphate ions assimilated into DNA/RNA/phospholipids/NADP/RuBP;
- Rate of absorption increased by mycorrhizae;
- Phosphate ions transferred through food chain;
- Some phosphate ions lost by excretion/when plants and animals die;
- Phosphorus containing compounds are decomposed by saprobionts/fungi;
- Weathering of rocks releases phosphate ions into seas and taken up by aquatic producers/algae;
- Phosphate ions passed along food chain to birds;
- Guano returns phosphate ions to soils
Describe the importance of
phosphorylation
(2)
- Makes substrates more reactive;
- Lowers activation energy for the reaction
Describe
eutrophication (6)
- Growth of algae / algal bloom blocks light;
- Reduced / no photosynthesis so (submerged) plants die;
- Saprobiotic (microorganisms / bacteria);
- Aerobically respire / use oxygen in respiration;
- Less oxygen for fish / aerobic organisms to respire;
- (So) they die;
Describe the function of saprobionts
releasing carbon dioxide (6)
- Microorganisms are saprobionts/saprophytes;
- Secrete enzymes (onto dead tissue) / extracellular digestion;
- Absorb products of digestion/smaller molecules/named relevant substance;
- Synthesis of structural compounds/named compound;.
- Respiration provides energy for growth
- Respiration (by microorganisms) produces carbon dioxide;
Evaluate use of fertilisers for
mycorrhizas (4)
(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;