The nitrogen cycle Flashcards
Where are biotic places nitrogen is found?
Plants, animals, decomposers, amino acids, proteins, nucleic acids, chlorophyll, phospholipids, ATP, NADP and NADPH
Where are abiotic places nitrogen can be found?
Atmosphere, soil nitrites, soil nitrates, soil ammonia and urea
What are the stages of the nitrogen cycle?
Assimilation, ammonifaction, nitrification, denitrification and nitrogen fixation
What is assimilation?
Plants absorb nitrate ions from soil and convert these into organic molecules containing nitrogen (amino acids)
What forms the source of nitrogen for animals?
Plant protein
How are animal proteins formed?
Gut enzymes hydrolyse to amino acids which are rearranged
What happens to excess amino acids?
They are lost in urine
What is ammonification?
Dead plants, animals and faeces are converted to ammonia by soil decomposers
What is ammonia a product of?
A waste product of saprophytic feeding
What does ammonia form?
Ammonium ions in solution in soil water
How can plant use ammonium ions?
As a nitrogen source
What is the equation for the formation of ammonium ions?
NH3 -> NH4+
What is nitrification?
Ammonium ions in well aerated soil are oxidised by soil bacteria and energy is released y the process for the bacteria
What type of process is nitrification?
Anaerobic process
What is an issue with nitrate ions?
They are easily washed out of soil into lakes or rivers
What is the equation for the formation of nitrite ions?
NH4+ + O2 -> NO2- + O2
What converts ammonium ions into nitrite ions?
Nitrosomonas
What is the equation for the production of nitrate ions from nitrite ions?
NO2- + O2 -> NO3-
What converts nitrite ions between nitrate ions?
Nitrococcus
What can oxidise atmospheric nitrogen into nitrates?
Lightening
What is the industrial process for nitrification?
The Haber-Bosch process
What is denitrification?
When there is soil with high nitrogen content that becomes anaerobic, nitrates are removed from the soil by a series of reactions that strips the oxygen away, producing nitrogen gas
What is the oxygen produced by nitrification used for?
Aerobic respiration
How is denitrification prevented?
Improving soil drainage
What are examples of soil bacteria?
Azotobacter and rhizobium
What does azotobacter do?
It reduces nitrogen into ammonia
Where is azotobacter found?
Free living in soil
What does rhizobium do?
It forms symbiotic relationships with legumes (peas, clovers) and causes growth of root nodules, which is an example of mutualism
Where is rhizobium found?
In roots
How is rhizobium an example of mutualism?
The bacterium gains carbohydrate and energy from the plant ad plant gains ammonia source
What type of process is nitrogen fixation?
Anaerobic
What is the result of nitrogen fixation being anaerobic?
Need to keep oxygen levels in cells low
What is the equation for the production of ammonia by rhizobium?
N2 + 6H+ +6e- -> NH4+
