5.4 Nutrient cycles Flashcards
What are saprobionts?
extracellular digesters that release mineral ions into the soil by feeding on dead and decaying matter
How do saprobionts digest DOM?
branching hyphae (mycellium) penetrate through the medium and secrete digestive enzymes and absorb the soluble products of digestion
What microorganism is the nitrogen cycle driven by?
bacteria - only cycle that is dependant on bacteria
What are all the chemicals of the N cycle?
N2 - nitrogen gas (very stable due to triple bond)
NH3 - ammonia (NH4+ - ammonium ions)
NO2- = nitrite
NO3- = nitrate
Why is N2 gas unavailable for most life?
it is very unreactive due to the stable triple bond
What ion do plants absorb in alkaline soils?
ammonium ions
What ion do plants absorb in acidic soils?
nitrate - NO3-
What are the 4 processes in the N cycle?
nitrogen fixing
ammonification
nitrification
denitrification
what is deamination?
amine group and hydrogen is removed from an amino acid - NH3
what is deamination?
amine group and hydrogen is removed - NH3
What is an example of deamination?
3.3 digestion - NH3 removed from an amino acid in the liver
What are nitrogen-fixing plants called?
legumes
What are nitrogen-fixing plants?
plants that have n-fixing bacteria growing in the root nodules
What is the nitrogen-fixing bacteria in the root nodules called?
rhysobium
How is nitrogen-fixing bacteria mutalistic bacteria?
plants get N compounds and bacteria gets C compounds such as glucose
How are N-fixing plants able to fix nitrogen (reaction)?
N2 —-> NH3
reduction reaction
enzyme = nitrogenase
What is the sequence of events of the N cycle starting from N2 in the atmosphere?
atmospheric pool of nitrogen —> nitrogen fixing N2 to NH3 can be taken up by plantsto make proteins (decomposition) —-> feeding - proteins in animals (decomposition) —> excetion = nitrogenous waste (urea) —> all decomposition contributes to DOM —> DOM and nitrogenous waste undergo ammonification = ammonia in soil (NH3) —-> nitrification = NO2- in soil —-> nitrification = NO3- in soil —> denitrification = N2 in atmosphere
What are the 2 nitrifying reactions?
both oxidation reactions:
1. NH3 —-> NO2-
2. NO2- —–> NO3-
What bacteria carries out ammonification?
saprobionts
What is the only process in the N cycle that has anerobic bacteria?
denitrification
Why do plants need nitrogen?
For ATP, nucleotides and amino acids synthesis
How can you identify plants that are living in nitrogen poor soils?
light green leaves and stunted growth
How does deforestation affect the nitrogen cycle?
leaving the stump = more DOM
soil quality decreases because N in soil is exposed to soil errosion and leeching
How does crop rotation improve soil fertility?
helps in restoring lots nutrients of the soil as the first crop plants use up all the nitrogen in the soil - farmers plant more legumes
How would large volumes of animal waste affecr the N cycle?
more organic matter produced for ammonification so more nitrates in the soil
How does using too much fertiliser affect the environment?
leeching of excess nitrates causes eutrophication