Nutrient cycles Flashcards
Why do living things require nitrogen?
To make proteins
To make nucleic acids
Why is nitrogen very inert?
Nitrogen triple bond is very hard to break
What is a symbiotic relationship?
a relationship in which organisms benefit eachother
Describe what happens in nitrogen fixation
Atmospheric nitrogen reduced to ammonia by bacteria
Ammonia then dissolves to form ammonium ions
Why is the relationship between leguminous plants and nitrogen fixing bacteria a symbiotic one?
The pea plants gain a source of useful nitrogen from bacteria to make proteins and the bacteria gains carbohydrates from the pea plants.
How can nitrogen gas be fixed by humans?
In the haber process N2+3H2 –> 2NO2
What is the natural process that fixes nitrogen by oxidising it to nitrate?
Lighting
What happens in nitrification?
Nitrifying bacteria oxidise ammonia to nitrate
What form do plants require nitrogen in?
Dissolved nitrates
What process do plants use to acquire nitrate ions?
Active transport
What happens in ammonification?
Microbial saprobionts break down proteins in detritus to form ammonia in two stages
What are the two stages in ammonification?
Microbial saprobionts digest proteins to amino acids using extracellular protease enzymes and then remove amino groups from amino acids using deaminase enzymes to form ammonia
What happens in denitrification?
The anaerobic denitrifying bacteria convert nitrate to nitrate to N2 and NOx gases
What is mycorrhizae?
Associations between the plant roots and beneficial fungi found in nearly all plants found on earth
What is eutrophication?
The addition of extra nutrients such as nitrate or phosphate ions to ecosystems
