cellular respiration vs fermentation

[tym]

Is fermentation a subtype of cellular respiration? I always thought cellular respiration refers to the process that requires oxygen (and with electron transport chain as the final step). Am I understanding it wrong?

The reason I asked this is that I saw the wikipedia page for cellular respiration (http://en.wikipedia.org/wiki/Cellular_respiration). It puts fermentation as one type of cellular respiration, and the process that requires oxygen was referred to as "aerobic respiration."

I guess I just want to know what the convention is. Thanks in advance!

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[pgoat]

I actually remember this being mentioned in a textbook--fermentation is technically a type of cellular respiration, though often 'cellular respiration' is used to refer specifically to aerobic respiration. I think it's understood that cellular respiration is an ambiguous term, so if it were on the MCAT there would probably be clarification.

 

[tym]

I actually remember this being mentioned in a textbook--fermentation is technically a type of cellular respiration, though often 'cellular respiration' is used to refer specifically to aerobic respiration. I think it's understood that cellular respiration is an ambiguous term, so if it were on the MCAT there would probably be clarification.

Thanks pgoat!! that makes sense

 

[lumpyduster]

I would also remember that glycolysis is anaerobic. Oxygen doesn't NEED to be there. Fermentation occurs if, for some reason (usually not enough O2), you can't do Citric Acid Cycle/Oxidative phosphorylation to make ATP and regenerate NAD/FAD for more glycolysis to occur.

 

[Shirafune]

Cellular respiration can be either aerobic or anaerobic. Aerobic respiration uses oxygen as the terminal electron acceptor in the ETC. Anaerobic respiration uses some other compound as the terminal electron acceptor in the ETC. Fermentation is necessary to replenish NAD+ when TCA/ETC cannot occur. Remember that glycolysis first uses 2 ATP (ATP -> ADP) to phosphorylate the sugar at two different steps: hexokinase (glucose -> G6P) and phosphofructokinase (F6P -> F1,6BP). After the 6C sugar is cleaved to form two 3C compounds, 1 NADH and 2 ATP are generated per 3C molecule. Therefore, the second step yields +2 NADH and +4 ATP, with glycolysis yielding a net +2 ATP and +2 NADH. NADH is produced when an aldehyde is oxidized to a carboxylic acid (NAD+ is reduced). ATP is produced when a phosphate is removed from the 3C molecule. Without NAD+, glycolysis cannot proceed.

If whatever terminal electron acceptor a cell uses is available, then TCA/ETC will occur. If not, glycolysis will be followed by fermentation.