Remember that reduction is the addition of electrons and oxidation is the removal of electrons. Electron transport involves components such as cytochrome. The last step of the electron transport chain transfers the leftover, low energy electrons to oxygen to form water. This last step is, of course, blocked by a lack of Oxygen, all the reactions back up and a person dies. Fermentation in humans only works in muscle and not in other cells so the other cells run out of ATP and everything stops.
Rotenone is a type of rat poison which blocks the first step of the electron transport chain.
The ATP synthase is reversible and can run in either direction. Bacterial cilia and flagella, but NOT those of eukaryotes, use a similar rotor system to spin the cilium or flagellum at more than 100 revolutions per second.