Flashcards in Energy without Oxygen Deck (24):
E. Coli respiration donors
E. Coli respiration acceptors
- O2 - best
Oxygen's redox potential
When using non-O2 acceptors
The cell always gets less energy
The next best acceptor
- 421 mV
Common characteristics of electron transport chains
- all start with low Eo' potential substrates
- end with higher Eo' substrates
- all employ electron carriers
- all contribute to the proton motive force.
All electrons will go through the ____ in the ETC
- quinone pool
- it's not necessary to match up a donor and acceptor
- uses normal respiratory chain
- but can grow anaerobically when O2 not available.
- only pumps 4 H+
- less ATP for anaerobic respiration
when NO3- available
- the respiratory chain is shortened, because the redox difference between O2 and NO2- is large.
- unable to utilize NADH as a respiratory donor
- H2 and formate are respiratory donors
- uses O2, NO3, NO2, DMSO, and possibly fumarate as acceptors.
Why we know there is at least one more donor?
- mutant strains that cannot oxidize either H2 or formate and these bacteria are able to grow on complex media, although not as well as wild type strains.
Geobacter and ferric iron
- Uses ferric iron to accept the electrons
- oxidizes formate to take e-
- 2 protons pumped but produces H+ outside to contribute to PMF
- reduces nitrate
- use a respiratory chain and F0F1 ATPase to make ATP
- chain begins and ends on the extreme reducing side of the redox tower
- starts with a reduced ferredoxin and ends with protons being reduced to hydrogen (H2)
- greater difference between the redox potential of donor and acceptor compounds = more protons pumped = greater potential for ATP synthesis.
Fumarate and Succinate
- can switch off being either the donor or acceptor
- but change the quinone pool
- change quinone from ubiquinone to menaquinol
When a bacterium runs out of electron acceptors
- it is forced to utilized SLS as its only source of ATP.
NADH becomes a problem
- NADH can only be harvested if an electron acceptor is available
- NAD+ must be regenerated
- TCA stops because it is also creating NADH
- Glycolysis becomes main energy generator, but the cell still requires 2 NAD+ to reduce to NADH
Products of bacterial fermentation
- lactic acid
- acetic acid
Electron Donors of C. jejune
Electron Acceptors of C. jejune
Enterobacter fermentation products
- yeast makes ethanol during fermentation under anaerobic conditions.