Expert: Dana Krempels, Ph.D. - 8/5/2011

Question
Hi,

I was hoping you would be able to help with my understanding of anaerobic respiration. I have read a number of articles on the subject. Many refer to glycolysis and subsequent fermentation reaction to produce lactate or ethanol and re-generate NAD. I am comfortable with this. I am also reasonably happy with the workings of electron carriers etc in aerobic ETCs.

However, some descriptions of anaerobic respiration refer to some prokaryotes using ETCs. I don't understand which prokaryotes would use ETCs and why (why don't all prokaryotes use ETCs?)/ for what NET gain of ATP? I also do not understand how the use of an ETC would fit into a prokaryotes respiration of glucose or other organic molecules. Do some prokaryotes perform glycolysis, then use their reduced NAD to directly enter an electron transport chain? Could you describe an example of how an ETC fits in following glycolysis?

Thank you very much for your help.

Best wishes,

John

Answer
Dear John,

Sorry for the delay in answering.  I've been trapped in the wilds of Idaho without internet access, but have found a library with WiFi.

I'm not a cellular/molecular biologist.  But as far as I know, both aerobic and anaerobic respiration employ electron transport chains.  The main difference between the two is that oxygen is not used as the electron acceptor in the anaerobic pathway, and some other molecule must be utilized.  The exact acceptor can vary among prokaryotes, and probably evolved with what was available and chemically usable as a terminal electron acceptor.

I'm not sure this completely answers your question, but there it is.

Dana