I had the following question on a bio test covering cell respiration and glycolysis, but I'm not sure if I agree with the answer.

When a molecule loses hydrogen atoms (as opposed to hydrogen ions), it becomes
B) oxidised

According to my textbook (Principles of Life, 2nd Edition), oxidation is defined as

Relative loss of electrons in a chemical reaction; either outright removal to form an ion, or the sharing of electrons with substances having a greater affinity for them, such as oxygen. Most oxidations, including biologial ones, are associated with the liberation of energy.

Hydrogen atoms have one proton and one electron in their typical state. If a molecule is losing hydrogen atoms, then its net charge wouldn't change. For example, if a (hypothetical) molecule had 7 protons and 6 electrons, it would have a charge of +1. If it then lost a hydrogen atom, it would now have 6 protons and 5 electrons, which still yields a net charge of +1. Am I missing some critical piece of information, or is this still considered oxidation?

  • $\begingroup$ Oxidation may be defined as the loss of electrons, and reduction as the gain of electrons. An ionization (loss of a proton) is neither an oxidation or a reduction, as no atom loses or gains electrons. Similarly, hydration (the addition of a water molecule, such as occurs in beta-oxidation: the reaction catalyzed by enoyl-CoA hydratase) is not in any sense an oxidation or a reduction, although this is often a source of confusion. When an atom loses hydrogen atoms it looses both protons and associated electrons. Hence it is an oxidation. $\endgroup$
    – tomd
    Commented Jan 14, 2017 at 2:10


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