How does the body actually transform and use energy from food?



How does the body actually transform and use energy from food?

In: Biology

Signaling hormones (especially growth hormone) causes an increase in metabolic rate and anabolic processes such as building proteins and such. That is how our body uses the ATP we generate from amino acids, fatty acids, and carbs to create building blocks for body development.

Your cells literally burn fuel like a fire or a car engine. They combine oxygen with hydrocarbons (fats, carbs, proteins) in a chain of chemical reactions that produces CO2, H2O and usable energy. It’s technically considered combustion! Every one of your cells is a tiny internal combustion engine.

through [metabolic pathways](, technically speaking i would consider them [non-trivial](, at an ELI5 level “there’s a long series of chemical reactions that end up with stuff your cells can use”

It essentially comes down to how “unhappy” the electrons still are in the food you consume.
Our body increasingly makes these electrons happier by allowing them to relax, and in-turn they pay us back by releasing energy – energy which we can capture, and use for other things (like making ATP).

A food with a lot of unhappy electrons has a lot of potential energy (chemical energy).
Electrons, which have a negative charge, are happiest when they’re *really* close to positive charges. The nucleus of an atom is full of positive charges (protons).

So, we have electrons that would *like* to be near protons, but how could we do that? If we could just do that, then the electrons will pay us back with energy.

Well, it turns out that not all elements are equally strong.
Some elements are *really* strong and thus, are *really* capable of pulling electrons in *very* tight and cozy to the nucleus (where all the positively charged protons are).
This makes those electrons very happy, and so they release energy. The closer an atom can pull an electron to its nucleus, the happier the electron, and thus the more energy it releases.

Every element has a “strength” value known as [Electronegativity](
Oxygen is the 2nd strongest element in the Universe (with a strength value of 3.44).
When we break down food (like sugars/carbs, or fats) and release energy from it, we’re “oxidizing” it. This means that we presented an opportunity to the electrons in food, to get closer to a nucleus. Oxygen being so strong, tends to be something we use a lot when attempting to satisfy the electrons, since with Oxygen being so strong, it’s able to pull the electrons nice and super tight to its nucleus. So we tend to present oxygen to unhappy electrons, to give them a really cool place to go.

This makes those electrons happy.
And so all the energy that they were using before to run around in “orbits” (vibrating) can finally be released. It has to be released because, you see, there’s a law in science that states energy cannot be destroyed – so if the electrons were unhappy before & running around with a lot of energy, and now we’ve made them very happy and relaxed, then the difference in energy has to be released (since it can’t be destroyed).

Our body (or, cells), simply surround these little energy release events with other molecules that are capable of absorbing that energy. They can then use this captured energy and use it to do other things – sort of like how a solar panel captures the extra energy released by the sun, and in-turn allows *you* to do other things with that captured energy (like charge your cell phone).

It turns out that ATP is a great molecule to use for capturing and storing energy. It’s a really great, hyper-efficient solar panel, so to speak. And so we use it to capture energy released from food. And then, later, when we need energy to fuel a process (like a chemical reaction) we can simply use the energy that was “charged into” the ATP molecule previously.

Thus, we will have ***transformed*** the energy from a food molecule, and turned it into energy in an ATP molecule, and then eventually ***used*** that energy to fuel the processes of the body.

Hope this helps!