We all know you need oxygen to live. But why? What happens to oxygen in our bodies? Why does it keep us alive? And maybe most importantly, why does it slowly kill us?

In today’s video, I explore the process of respiration, how it’s weirdly similar to fire, and why we rely on one of the most corrosive elements in the universe to survive. It gets weirdly existential.



What is it about fire? What is it about the dancing of the flames that you can’t help but get lost in them? Why do we gather around and stare at them in groups? Sure, we gather around them for warmth, but go to any campfire, everyone’s staring at it. We can stare into a fire for hours, it can hold our attention as well as any TV show.

Maybe we’re just drawn to non-repeating patterns. Maybe there’s something about the color that is especially pleasing to our eyes. Maybe we’re just moths.

There are some who believe that fire is what made us who we are. That once we learned to control fire, it not only changed how we ate, making it possible to get more nutrition out of food, but also that watching fires stimulated our brains, gathering around the fire provided opportunities to bond and communicate with others, share ideas, and all this extra stimulation grew our prefrontal cortex and made us humans.

Our connection to fire goes way deep, in fact, the chemical reactions that power our cells and bodies are very similar to the ones that are involved with combustion. We are, in a very real sense, living fire.

There’s a toxic substance that surrounds you all of the time. It’s in the air you breathe and the water that you drink. It’s in every cell in your body. And it’s slowly eating away at you.

I’m not talking about that feeling of imminent doom. Though it’s there.

I’m talking about oxygen, something you probably don’t think twice about… until you can’t breathe.

We all know we can’t live without oxygen, that oxygen is essential for life, at least life as we know it on this planet. But… why?

What exactly does it do after we breathe it in? Why did we evolve this way, and where did it come from in the first place?

I don’t know about you but I’d never really thought about it. Then I did. Turns out it’s really interesting. Interesting in a, “oh, cool a new existential crisis” way.

So let’s start with what you already know.

The majority of oxygen on our planet comes from photosynthesis. Plants and trees take in carbon dioxide and release oxygen.

And then we breathe in oxygen and release carbon dioxide. That they turn back into oxygen. It’s the great oxygen cycle that powers our world.

The oxygen cycle that is interconnected with the carbon cycle because CO2 is just an oxygen molecule with a carbon on it.

Sunlight hitting water vapors can also produce oxygen by splitting it off of water molecules.

But the biggest producer of the planet’s oxygen supply comes from one of Earth’s tiniest organisms: Prochlorococcus.

This species found in the oceans produces up to twenty percent of the oxygen in our biosphere.

In fact, scientists estimate that the ocean is responsible for up to eighty percent of our oxygen supply.

But the world hasn’t always been like this.

Before about 2.4 billion years ago, there was very little oxygen in the atmosphere, it was mostly nitrogen, carbon dioxide and methane.

And the oceans may have been green and not blue, because of all the iron in them.

And there was single-celled life at this time, but it was anaerobic life, meaning it doesn’t need oxygen.

But then, about 2.4 billion years ago, some photosynthesizers showed up, specifically cyanobacteria, which used the sun to convert that carbon dioxide and water into energy.

And the waste product of this reaction was oxygen.

This new way of making energy was super efficient compared to everything else and cyanobacteria just took over the world, each one of them farting out oxygen in what scientists call the Great Oxygenation Event.

All that oxygen in the atmosphere killed off the anaerobic microbes, and the world changed dramatically.

There was less carbon dioxide in the air. Temperatures dropped. And most of the life that was around was pushed to extinction.

(maybe a microbe with an RIP across it)

Which is sad. Poor little anaerobic bacteria. But, these changes led to an explosion of genetic diversity and set the world on the course to make us. So yeah… Big mistake.

So okay, that’s where oxygen is from but where is it FROM?

Well Oxygen has 8 protons so like anything bigger than hydrogen or helium, it comes from supernova explosions that scatter it out amongst gas clouds that eventually coalesce into planets like big blue here.

And oxygen is the universe’s third most abundant element, after hydrogen and helium.

And oxygen has been around quite a while.

A team of astronomers published a paper in The Astrophysical Journal Letters in 2020 describing how they detected large amounts of oxygen in an ancient star.

The star, which has the catchy name of J0815+4729 is an elementally depleted star located more than 5,000 light years away toward the Lynx constellation.

The astronomers suggest that the star’s primitive composition shows that it was formed “during the first hundreds of millions of years after the Big Bang, possibly from the material expelled from the first supernovae of the Milky Way.”

So yeah, the oxygen you’re breathing right now, it’s old, it’s ancient, it’s got… wisdom. Listen to your breath… and you can hear the wisdom of the universe…

Anyway, so we’ve got its origin story, now what makes it so special?

Like, why does it support combustion? Why does fire need it to burn? What makes it so reactive? How does it cause rust?

Concerning combustion… There are three things required to create it:

  • Fuel – something that burns
  • Energy – what starts the reaction
  • Oxidizer – a molecule that accepts electrons


Wait, what?

Okay, so this is the best way that I can make sense of it but please keep in mind that this kid (hold up old photo) really struggled in chemistry class.

Those of you who follow space stuff probably know that thermal management is a big part of space travel because in space there’s no air for the heat to conduct into.

That’s why the ISS has heat exchangers and radiators to prevent it from getting too hot.

Well, combustion is basically fuel donating electrons.

And just like heat on the space station, those electrons need someplace to go. And not all molecules have room to accept any electrons.

But oxygen does. And here’s why…

Oxygen in a neutral state has eight protons and eight electrons, with the protons shmooshed together in the nucleus and the electrons configured in shells of two and six, but it wants to have eight electrons in its outer shell.

This makes it electronegative. It wants to steal from atoms that give up their electrons so it can complete its outer shell.

And look, I know I’m being really simplistic with the language here but this guy here was too busy drawing in class so this is the best I can do.

So fire is the visible effect of combustion. A fuel with electrons to spare meets a source of energy, oxygen takes the electrons. The fuel is transformed, and what’s left over is smoke. And ash.

Another visible effect of combustion is rust.

Rust is known as iron oxide because it is iron that has been oxidized.

Rust is an example of corrosion, which is an electrochemical process that involves an anode, a piece of metal that gives up electrons, an electrolyte, and a cathode, a piece of metal that accepts electrons.

As the metal corrodes, the electrolyte offers oxygen to the anode. When oxygen combines with the metal, the electrons are freed.

As they move through the electrolyte to the cathode, the anode’s metal transforms. And what’s left over is rust.

By the way if some of that sounds a lot like how a battery works… Yeah. It’s the same principle that batteries work on.

Basic overview

And, in a similar but different way, this is what’s happening in your body.

When you eat, oxygen oxidizes the food to generate energy by combining itself with sugars.

So what happens is when we digest food in the gastrointestinal tract, those sugar molecules pass into the blood.

The blood moves the molecules to the cells, and mitochondria break up the molecules’ chemical bonds to release energy.

Cells needs oxygen to complete this process.

So at the same time that your guts are breaking down those sugars and passing them through the bloodstream, your lungs are breathing in oxygen..

This oxygen travels through tubes in your lungs called bronchi. These branch off into smaller tubes called bronchioles.

Tiny air sacs called alveoli are at the end of each bronchiole. Tiny blood vessels called capillaries cover the alveoli.

This is where the oxygen gets passed into the blood.

The oxygenated blood travels to the heart, which pumps it out to the cells in the body. Once in the cells, it combines with those sugars in the mitochondria.

And this is called cellular respiration.

Sugars in food are converted into simple sugar glucose, and the energy stored in glucose is transferred to adenosine triphosphate (ATP), an organic compound.

Similar to how fire uses oxygen to burn, the mitochondria use it to convert glucose into ATP, again, by stealing electrons. What’s left over is carbon dioxide and water.

The blood delivers carbon dioxide to the capillaries, the alveoli move it into the lungs, and then you exhale and remove it from your body.

So our bodies rely on one of the most corrosive elements on the periodic table to live. Unsurprisingly, that takes a toll over time.

We breathe an average of 22,000 times per day. Most of the time, the transfer of oxygen to the blood goes smoothly, but things go a bit wonky around two percent of the time.

This is when our metabolism produces free radicals, which are oxygen atoms with an unpaired electron.

Free radicals are unstable and try to pair up with any atom for stability. They may attack lipids, proteins, sugars, and nucleic acids.

And this is what antioxidants are for. They’re compounds that prevent the creation of free radicals. And this is something our bodies make naturally, but but when there is an imbalance between the two, cells experience oxidative stress.

This is one of the major contributors to aging-related diseases like:

  • Cancer
  • Alzheimer’s disease
  • Chronic fatigue syndrome
  • Diabetes
  • Inflammatory disorders
  • Male infertility
  • Parkinson’s disease

According to the free-radicals theory, superoxide and other free radicals damage a cell’s components.

Constant maintenance is required, but over time the damage becomes too much for the cell to handle and it starts to lose its ability to properly function.

And while studies over the years on how much antioxidants can increase longevity have been inconclusive, one mitochondrion waste product may help delay aging.

Take it deeper – what it all means

So, that’s where oxygen came from, how it took over the world and how it both keeps us alive and is slowly rusting us. It giveth and taketh away.

On this planet anyway. There might be conditions on other planets that would favor some other oxidizer. Fluorine is also electronegative, but violently so, it explodes when exposed to air.

But maybe in a different environment with higher pressures and temperatures and whatnot, maybe it would combust in a more measured way like oxygen does here.

Regardless, when we look for habitable planets, we still look for oxygen because we know at least one form of life that farts it out. But even still, oxygen isn’t proof that there’s life on a planet.

I mentioned earlier that oxygen can be made with photosynthesis but also it can be split off of water vapor molecules by solar radiation.

It is possible if a warm ocean planet is too close to its star, it could get hit with enough UV radiation to create a decent amount of oxygen and hydrogen.

The hydrogen escapes to space and leaves oxygen behind. Over time, a thick oxygen layer builds up and entire oceans disappear. So you could have a lifeless planet with a lot of oxygen in the atmosphere.


So yeah, in a lot of ways the same forces that produce that campfire that may have shaped humans into what we are today, are working inside of us our entire lives. Maybe that’s why we have such a connection to fire, because we are a kind of fire.

We are basically a very complicated way of making this (hold up food) give its electrons to bacteria farts. Until the bacteria farts kill us.

Bon apetite.


Add comment

Your email address will not be published. Required fields are marked *