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I get that oxygen is the terminal electron acceptor in oxidative phosphorylation. But why is it essential to accept these electrons and remove them as $\ce{H2O}?$

Oxygen is essential for cellular respiration, but after learning about cellular respiration it seems oddly unimportant. Why is having an efficient garbage collector (oxygen picking up the used electrons) so crucial to cellular respiration, and to ATP production?

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    $\begingroup$ Where would you put the said electrons otherwise? $\endgroup$
    – Ivan Neretin
    Commented Dec 28, 2019 at 18:27

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I get that oxygen is the terminal electron acceptor in oxidative phosphorylation. But why is it essential to accept these electrons and remove them as H2O?

A redox reaction is made of two half reactions. Neither one of them is more or less important; the combination of both determines the energetics of the reaction.

Why is having an efficient garbage collector (oxygen picking up the used electrons) so crucial to cellular respiration, and to ATP production?

The electrons are not "used" as in an old car or worn-out clothes. There as shiny and new as before. Without oxygen, the reaction would not happen in the first place (electrons are transferred from less tightly bound to more tightly bound). The Gibbs energy of proton transport matches what is necessary for ATP synthesis, which in turn matches the Gibbs energy of the redox reaction. With a different electron acceptor (specificities of the enzymes involved aside), the proton gradient might be too weak to make ATP.

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Oxidative phosphorylation consists of electron transport chain and chemiosmosis. During electron transport chain, electrons transfer causes the energy production and forms an electrochemical gradient. Then, during chemiosmosis, the energy produced during this electrochemical gradient is used to synthesize ATP.

So, why oxygen is needed in electron transport chain. If oxygen is not present there to accept electrons, the electron transport chain will stop taking place, and ATP formation by chemiosmosis will stop. And lack of ATP will lead to cell death.

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    $\begingroup$ For some reason it seems less dramatic than i expected lol. It seemed like I must have had something wrong. But thanks for the response, I wasn't confident in that really being the right answer. Oxygen is needed to prevent the ETC from getting clogged with used up electrons, thus continuing ATP production. Which is definitely important. Oxygen is one hell of a garbage truck. Thanks again! $\endgroup$
    – Nolan Fehon
    Commented Dec 29, 2019 at 20:59

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