Why isn't Fluorine, or Neon, the final electron acceptor in cellular respiration?

Question

I'm a Chemistry student learning about periodic trends. I know that in (many organisms') cellular respiration, oxygen serves as the final electron acceptor due to its high electronegativity.However, applying the periodic trends, fluorine is more electronegative than oxygen, and the noble gas neon even more so than fluorine. Why aren't either of these the final electron acceptor? I know that in some organisms, the final electron acceptor is sulfur. But I've never heard of it being fluorine or neon. Why?

Answer 1

Hi there! This is actually a really good question but the answer may be less complex than you think. Simply put, these atoms are not as abundant and readily available as oxygen (or sulfur for non-aerobic organisms). Cellular respiration happens within seconds and we don't realize how constant that need for oxygen truly is. Don't try this, but if someone stopped breathing in oxygen their body would very quickly have to shut down because that constant supply to the process of cellular respiration is necessary for organisms to function. Oxygen (and as you mentioned, sulfur) has become the atom to take on that role as electron acceptor because that is the electronegative atom that we have access too. I'm sure if we lived in some kind of environment where we "breathed" in molecules with fluorine or neon, organisms would have evolved to use those atoms in their cellular respiration. Cool question, I've never considered it before.