Nitrate reduction Flashcards
Does anaerobic respiration use electron transport chains?
Yes
Does anaerobic respiration generate a PMF?
Yes
What is the terminal electron acceptor of anaerobic respiration?
An inorganic molecule that isn’t O2
What are 4 possible terminal electron acceptors of anaerobic respiration? What are they reduced to?
Nitrate: reduced to nitrite or nitrogen gas
Ferric iron (III): reduced to iron (II)
Sulfate: reduced to hydrogen sulfide
Carbonate: reduced to methane and acetate
Why isn’t anaerobic respiration as good as aerobic respiration?
The TEA aren’t as electropositive, so the electrons from NADH and FADH2 don’t release as much energy when they go through the ETC
Is anaerobic respiration better than fermentation for energy production?
Yes, produces way more ATP
What is the terminal electron acceptor of nitrate reduction?
Nitrate
What is the first step of nitrate reduction?
Nitrate reduction by nitrate reductase to produce nitrite
Do all nitrate-reducing bacteria go to the end of the pathway?
No, some only do the nitrate reduction and stop, then excrete the nitrite as waste
What conditions need to be present for nitrate reductase to be expressed?
Absence of oxygen and the presence of nitrate
Why is the absence of oxygen required for nitrate reduction to occur?
If there’s oxygen around, the bacteria will use aerobic respiration instead because it generates more energy
Why does nitrate reduction produce less PMF and ATP than aerobic respiration?
Nitrate isn’t as electropositive as oxygen, so there isn’t as many steps in the ETC before the electrons reach NO3-. There are fewer proton pumping events, so less PMF is generated, and less ATP is produced
What is the full nitrate reduction pathway?
Nitrate (NO3-) -> nitrite (NO2-) -> nitric oxide (NO) -> nitrous oxide (N2O) -> nitrogen (N2)
What is denitrification?
The rest of the nitrate reduction pathway. Involves the conversion from fixed nitrogen to gaseous nitrogen
Why would a bacteria want to do denitrification?
Involves an extra proton pumping event, so generates a little more PMF and a little more ATP
