Where is the line between Anaerobic and Aerobic? I am well aware of traditional anaerobic respiration (lactic acid or alcohol produced - no Krebs cycle) and traditional aerobic respiration (O2 is used at the end of the Citric acid cycle). I am wondering how to classify respiration that uses the Citric acid cycle, but consumes a nitrite/ate or sulfite/ate instead of O2. Is that anaerobic or aerobic? !NADH and Nitrite I could only find this image on Google image search catch but it said it was from <

Your question is based on a bit of confusion about electron acceptors that is very common and that drives microbiologists crazy. Energy (as ATP) is generated when electrons are moved from an electron donor to an electron acceptor. In respiration, the electron acceptor is inorganic -- oxygen for aerobic respiration or an inorganic molecule such as sulfate or nitrate for anaerobic respiration. Use of an organic molecule such as pyruvate as an electron acceptor is properly called fermentation. Both anaerobic respiration and fermentation are termed anaerobic because they don't use oxygen. Any introductory microbiology textbook will cover these concepts in detail, because they are important to understanding the metabolic diversity of bacteria. Brock Biology of Microorganisms is a good text.