Microbial Bioenergetics Flashcards
What does a reducing agent do? Inc example
- donates electrons to other species so it has been oxidised
- Hydrogen
- NADH
What does an oxidising agent do? Inc example
- accepts electrons from another species so it has been reduced
- Oxygen
- NAD+
Whats the difference between mitochondria in bacteria compared to eukaryotic cells?
- in eukaryotic cells the mitochondria is supplied with constant levels of oxygen
- bacteria doesn’t have a problem of transporting ATP/ADP/Pi/NADH in and out of the mitochondria as mitochondria is the bacterium and so they are present
How does bacterium adapt to low/no oxygen?
- use alternative to O2, an alternate electron acceptor (CO2, S, Sulfate SO42-, NO3-, NO2-, Fe3+)
- using light energy (no need for O2, need electrons to reduce the CO2 in photosynthesis)
- increase the affinity for O2 (less protons pumped)
How can bacteria pump 5H+ in complex one in the mitochondria compared to the livers 4H+?
- there is an additional subunit
- allows pumping of 5 not 4 protons
- recent discovery
How does Paracoccus denitrificans adapt to the varying concentrations of Oxygen?
- has 3 different paths to oxygen that have different affinities for oxygen
- Paracoccus can do the same route as eukaryotic mitochondira
- it can also use electrons from complex 3 to oxygen making less ATP but using a lower conc of oxygen
- it can use electrons from complex 1 also, has a even higher affinity for oxygen so can have a lower conc present, but less ATP is used
- 3 branches present (can work in parallel dependent on the varying conc of O2 present)
How does Paracoccus denitrificans adapt to there being no oxygen present?
Uses alternative electron acceptors.
- NO3- (nitrate) two branches to nitrate are available, all coming from Q (only using complex 1)
What happens during denitrification in Paracoccus denitrificans?
Reduction of the nitrate compound from the fully oxidised to the oxidation state of N2 or ammonia (NO3- to NO2- to NO to N2O to N2)
Difference between how Paracoccus respires compared to mitochondria?
- can use the same linear pathway as the mitochondria
- also has branches/ additional steps that give it flexibility as it has alternatives to Oxygen
- mitochondria has 4 e donors and 1 e acceptor whereas Paracoccus has 10 e donors and 5 e acceptors
What is different about E.coli’s respiratory chain compared to the liver or paracoccus?
- missing complex 1, therefore no Q cycle
- only 2 energy conserving steps instead of 3, making less ATP
(not much oxygen in the gut anyway) - can replace quinone with DMK (demethylmenaquinone) or MK (menaquinone)
How is E.coli’s respiratory chain similar to Paracoccus?
- it has a branched aerobic respiratory chain
- low oxygen affinity branch, more ATP
- flexibility / adaptability as there are many inputs and outputs
What are the different e input (E donors) for E.coli?
- can use hydrogen/ formate, NADH, Lactate, G3P, succinate, pyruvate
What are the different e outputs (E acceptors) for E.coli?
- thiosulfate, fumarate, nitrite, nitrate, oxygen
Describe the respiratory chain of E.coli.
2 steps of energy conservation
2 branches with each step
- 2 different NADH dehydrogenases (NDH1 and NDH2)
quinone pool in the middle
- 2 terminal oxidases, Cyt bo3 and Cyt bd
Describe the 2 NADH dehydrogenases in E.colis respiratory chain.
NDH 1 - proton pump - 4H+ per NADH - integral membrane protein NDH-2 - no proton pump - membrane bound - no ATP made when oxidising NADH onto quinone
