|MadSci Network: Microbiology|
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 amazon.com for about $75. An excellent overview of cellular respiration can be found online at: http://www.geocities.com/CapeCanaveral/Lab/2041/ 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
Try the links in the MadSci Library for more information on Microbiology.