How does the body switch between aerobic and anaerobic respiration?

Question

Lets take the case of a person doing heavy exercise. Aerobic respiration is taking place, but oxygen is about to be finished up. Glycolysis occurs, Krebs cycle finishes. Now NADH and FADH₂ enter electron transport system (ETS) to form ATP, but at the last step, cytochrome c oxidase cannot get oxygen as it just finished up. Now, what happens to the ongoing ETS? Does it go in reverse order and then arnon cycle to get back Acetyl co-A and respire anaerobically, or does this process get paused and respiration switches over to anaerobic mode till oxygen supply is replenished?

Answer 1

oxygen never really disappears unless you are holding your breath or otherwise being deprived of it for a long period of time. hemoglobin holds onto oxygen and releases it as needed by the body. as the body’s requirements go up, more oxygen dissociates from the hemoglobin molecules. in extreme situations, myoglobin (which has a much higher affinity for oxygen) may start to release the oxygen molecules it has bound. unless you drastically change the partial pressure of oxygen in your body or have some other diffusion problem it is very difficult to become that low on oxygen