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> Humans and many other organisms get electrons from food and expel them with our breath.

What




It sorta make sense as a redox reaction https://en.wikipedia.org/wiki/Redox , but it's more difficult to explain in easy terms than what I though.

For simplicity, let's imagine that you eat methane. The reactions is

  CH4(food) + 3 * O2(air)  --> CO2 + 2 * H2O
For simplicity, let's imagine that The Carbon, Hydrogen and Oxygen are more "happy" when they are in a state like in CO2 and H2O. And for simplicity, you split the bound in the molecules and assign a fictional charge to the atoms

  CO2 ~~> C{4+} + 2 * O{2-}
  H2O ~~> 2* H{+} + O{2-}
So in the "happy" state:

* the Oxygen has a fake charge or -2, i.e. it has two additional electron.

* the Carbon has a fake charge or +4, i.e. it has four electrons less the neutral version.

* the Hydrogen has a fake charge or +1, i.e. it has one electron less the neutral version.

Now, how do you decompose the methane in the food:

  CH4 ~~> C{4+} + 4* H{+} + 12 * e-
[Important: This is not the standard notation. Don't use it in a midterm!]

So if you decompose the methane molecule using "happy" atoms, it has 12 more electrons than what you expect. So in some sense, with each methane molecule you get 12 additional electrons.

The oxygen molecule decompose as

  O2 ~~> 2* O{2-} - 4 * e-

Note the minus sign. Each one "wants" 4 electrons.[Important: This is not the standard notation. Never ever a minus operator in a midterm!!!]

So the 12 electrons travel from the methane in the food to the oxygen you have breathed. (I'm not so convinced to use "expel" here.)

With more realistic food the equation is bigger an more difficult, the number of electrons and oxygens molecules change, but it's the same idea.

You can even follow how the electrons travel in the reactions in the mitochondria, https://en.wikipedia.org/wiki/Electron_transport_chain in each step they release a small amount of energy that is collected. [This is a technical detail of the biological part, you can't release a lot of energy altogether and pack it later.]

[Important: Again, this is not the standard notation. Use the standard notation in a midterm. The question was more difficult to explain than I expected I had to use not standard notation. I hope it's clear enough to read the standard notation and understand the idea.]


I feel bad for making you write all this out.

This is still not "get electrons from food and expel them with our breath", is it? We are not stocking up electrons in our bodies, using them somehow, then exhaling spent electrons.

What we are doing is taking in matter with a certain amount of chemical potential, putting out matter with less chemical potential, and capturing the difference. Electrons are intimately involved in this, but they're a bit of an implementation detail.


If you think it as a battery of a fuel cell, you care about the voltage and the charge, not about if it has Lithium or not. In general in the redox reactions (and in batteries) you don't care too much to which atom the electrons are bound (unless you have to build one). So the electrons are the important thing and the molecules are the implementation detail.

> What we are doing is taking in matter with a certain amount of chemical potential, putting out matter with less chemical potential, and capturing the difference. Electrons are intimately involved in this, but they're a bit of an implementation detail.

You are totally correct too. :) It's equivalente to the previos point of view where the electrons are the important part and the molecules are the implementation detail. It is just that sometimes it is easier to think from one point of view and other times it's easier to think from the other point of view.

(Essentially, Volt = Energy / Charge. Since the charge of the electron is fixed, you can convert easily (or use eV to measure the energy).)

---

If you think about the methane as a charged battery and the carbon dioxide as a discharged battery, then the idea is that the high potencial electron comes from the food and go away as low potencial electrons in the breath. I'm not 100% happy with this analogy, I think I understand it, but I'm not happy. You are not accumulating electrons.


When you lose weight, the biggest result of burning fat is carbon dioxide which gets expelled through your breath

https://www.medicalnewstoday.com/articles/287046.php


Yes. Same as how plants put on weight from absorbing carbon dioxide from the air. This still doesn't amount to "get electrons from food and expel them with our breath".




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