Chapter 31: Amino Acid Synthesis Flashcards
Why is nitrogen important?
- it is an essential component of DNA, RNA, proteins
- all organisms require it to live and grow
- majority of Earth’s atmosphere is N2
How much of the atmosphere is made up of nitrogen?
78%
Why is most of the nitrogen in the atmosphere unavailable for use by organisms?
Because the strong triple bond between the N atoms in N2 molecules make it inert.
What form does nitrogen take in the atmosphere?
N2
What is the Nitrogen Cycle?
The process of converting nitrogen into compounds that can be used by plants and animals.
What are the four processes of the Nitrogen Cycle?
- Nitrogen Fixation
- Ammonification
- Nitrification
- Denitrification (converting back to N2)
What is nitrogen fixation?
The process in which N2 in the atmosphere breaks and combines with other compounds.
What must nitrogen be combined with to become ‘fixed’ and what is the product of the fixation?
Combined with Hydrogen to make Ammonia (NH3)
OR
Combined with Oxygen to make Nitrous Oxide (N2O)
What are the 3 ways to ‘fix’ nitrogen?
- Bacteria convert nitrogen gas (N2) to ammonia (NH3) to be used by legume plants (peas, beans)
- Lightning strikes convert N2 to N2O or NO3
- Industrial production where chemical manipulation turns N2 into NH3 (fertilizer)
Which of the 3 ways to ‘fix’ nitrogen is the main process?
Bacteria converting N2 into NH3
Why is industrial processing of nitrogen difficult?
Because it requires lots of energy (must be mixed with H2 over iron catalyst at 500C and 300atm pressure).
What enzyme do bacteria use to convert N2 to NH3?
Nitrogenase
What are the 2 types of bacteria that fix nitrogen?
- Rhizobium
- Azobacter
- Cyanobacteria
Where do Rhizobium bacteria live?
In the root nodules of leguminous plants
What are Azobacter bacteria associated with?
The rooting zone of plants in grasslands
What is unique about Cyanobacteria?
They are nitrogen and carbon fixers (are photosynthetic).
About how much N2 is fixed per year by bacteria?
10^11 kg per year
How do bacteria use the nitrogenase enzyme to convert N2 to NH3?
Reaction involves splitting N2 and adding hydrogen to make ammonia.
N2 + 8H + 16 ATP -> 2NH3 + H2 + 16 ADP + 1 Pi
How much ATP do bacteria use to convert N2 to NH3?
16 ATP
What are the components of the nitrogenase enzyme complex?
- Reductase= provides high energy electrons for reducing power
- Nitrogenase= uses electrons to reduce N2 to NH3
What form do electrons provided by the reductase part of the nitrogenase complex take?
The form of ferredoxin
What is the process of ammonification?
After living organisms use organic nitrogen and die, decomposer bacteria convert the nitrogen to ammonia.
What is the process of nitrification?
The process that converts ammonia (NH3) to nitrites (NO2) and nitrates (NO3).
*ammonia comes from both nitrogen fixation and ammonification
How is the process of nitrification performed?
Performed by bacteria
What is the process of denitrification?
Process where nitrogen compounds convert back into atmospheric nitrogen (N2 or N2O).
Why is the process of denitrification necessary?
In order to prevent depletion of nitrogen from the atmosphere.
How is denitrification performed?
Mainly by bacteria, also by burning fossil fuels.
What organism is required in every step of the nitrogen cycle?
Bacteria!