18 Questions
What type of organisms are responsible for most nitrogen fixation?
Prokaryotes
In addition to prokaryotes, nitrogen can be fixed abiotically by which of the following?
Lightning
Which of the following is NOT a method used by some nitrogen-fixing bacteria to establish symbiosis with plants?
Triggering nitrogen fixation through light exposure
What is the purpose of the root exudates from legume plants in symbiotic nitrogen fixation?
Attracting nitrogen-fixing bacteria
Which of the following is true regarding symbiotic nitrogen-fixers?
Some require a close association with a host to carry out nitrogen fixation.
What characteristic distinguishes aerobic nitrogen-fixing bacteria from anaerobic ones?
Energy source used
What is the name of the enzyme complex responsible for the reduction of N2 to NH3 in nitrogen-fixing organisms?
Nitrogenase
Why is nitrogenase sensitive to oxygen?
It deactivates the enzyme complex.
Which structure in cyanobacteria provides a low-oxygen environment for the nitrogenase enzyme?
Heterocyst
How do some photosynthetic nitrogen-fixers protect their nitrogenase from oxygen while carrying out nitrogen fixation?
By fixing nitrogen only at night
Where do genes for nitrogenase have been found globally distributed, including in aerobic habitats and anaerobic environments?
In various habitats including oceans, lakes, soils, termite guts, and more
What characteristic distinguishes symbiotic nitrogen-fixers from other nitrogen-fixers that help them carry out nitrogen fixation efficiently?
Association with another organism to create a low-oxygen environment
What is the significance of the broad distribution of nitrogen-fixing genes among organisms?
It suggests a broad range of environmental conditions for nitrogen-fixing organisms.
Which process converts ammonia to nitrite and then to nitrate in the global nitrogen cycle?
Nitrification
What type of microorganisms are responsible for the oxidation of ammonia to nitrite in nitrification?
Ammonia-oxidizers
Why are aerobic ammonia oxidizers considered slow growers?
Their metabolism produces a small amount of energy.
In nitrification, what is the intermediate compound formed during the conversion of ammonia to nitrite by ammonia-oxidizers?
Hydroxylamine
What distinguishes aerobic ammonia oxidizers from other organisms in terms of energy source?
They use ammonia as an energy source.
Test your knowledge on nitrogen fixation processes carried out by both prokaryotes and abiotic factors such as lightning and industrial processes. Learn about the different types of nitrogen-fixing organisms and their symbiotic associations with hosts.
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