MadSci Network: Microbiology

Re: In cellular respiration, how does oxygen enable bacterial cells to release

Date: Mon Feb 22 16:23:54 1999
Posted By: David Eckert, Undergraduate, Dept. of Microbiology, BS Molecular Biology, Brigham Young University
Area of science: Microbiology
ID: 917638845.Mi

Thanks for the question, and please excuse the tardiness of this reply.

The answer to your question all lies in chemistry, which is not my best 
area, but I will do the best I can.

In the absence of oxygen, only certain chemical reactions can occur in a 
bacterial cell.  With this limitation, the reactions the bacterial cell can 
use to break down glucose and produce ATP only result in a net production 
of 2 ATP per molecule of glucose.  There is a lot more energy left in the 
glucose molecule, but the bacterium is unable to extract it because of 
chemical limitations.

In the presence of oxygen, however, a type of reaction called an 
oxidation-reduction (or Redox) reaction can occur.  This reaction involves 
the transfer of electrons between molecules.  With this ablility, the cell 
sets up what is called an electron transport chain. This chain of reactions 
allows the cell to get more energy out of the glucose, with a much larger 
net production of ATP.

In a nutshell, without oxygen, oxidation reactions cannot occur and only 
minimal breaking down of glucose occurs.  With oxygen, an electron 
transport chain is produced that is much more efficient and can extract 
more energy from each glucose.

If you are interested in knowing specifics about these reactions, a good 
introductory book on advanced molecular biology is "Molecular Biology of 
the Cell" by Bruce Alberts et al.  You can find it or a similar textbook at 
any college library.  If you are really serious about studying molecular 
biology on your own, you can order it from any college bookstore or get it 
at for about $75.  

An excellent overview of cellular respiration can be found online at:

This site has step by step diagrams of the chemical reactions in 
the electron transport chain and other stages in cellular respiration.

I hope this answers your question.  Good luck, and I hope you have fun 
learning about the fascinating world of molecular biology. 

Dave Eckert

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