Name: Why Are You Alive – Life, Energy & ATP
Uploaded: 2020-05-11T19:25:18.000Z
Duration: 11 min 30 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Adverbs of degree

At this very second, you are on a narrow ledge between life and death.

Adverbs of manner

You probably don't feel it, but there's an incredible amount of activity

Picture yourself as a Slinky falling down  an escalator moving upwards.

The falling part represents the self-replicating processes of your cells.

The escalator represents the laws of physics driving you forwards.

To be alive is to be in motion but never arriving anywhere.

If you reach the top of the escalator, there's no more falling possible, and you are dead forever.

Somewhat unsettlingly, the universe wants you to reach the top.

How do you avoid that? And why are you alive?

A cell is a piece of the dead universe that separated itself from the rest so it could do its own thing for a while.

When this separation breaks down, it dies and joins the rest of the dead universe again.

Unfortunately, the universe would like for life to be done with doing its own thing.

For some reason, it's not a fan of exciting things, but tries to be as boring as possible.

We call this principle "entropy," and it's a fundamental rule of our universe.

It's pretty complicated and counterintuitive, so we'll explain it in detail in another video.

For now, all you need to know is living things are inherently exciting.

A cell is filled up with millions of proteins and millions more simpler molecules like water.

Thousands of complex, self-replicating processes are happening up to hundreds of thousands of times every second.

To stay alive and exciting, it has to constantly work to keep itself from achieving entropy and becoming boring and dead.

The cell has to maintain a separation from the rest of the universe.

It's doing this, for example, by keeping the concentration of certain molecules different on the inside and the outside

by actively pumping out excess molecules.

To do stuff like this, a cell needs energy.

Energy is the ability of things in the universe to do work; to move or manipulate a thing; to create change.

This ability cannot be created or destroyed.

The set amount of energy in the universe will never change.

So, billions of years ago, one of the most crucial challenges for the first living beings was to get usable energy.

We don't know a lot about the first cells, except that they got their energy from simple chemical reactions.

And they found the ultimate energy transfer system: the energetic building block of life.

The molecule Adenosine Triphosphate, or ATP.

Its structure makes it uniquely good at accepting and releasing energy.

When a cell needs energy, for example, to pump out molecules or to repair a broken micro machine,

it can break down ATP, and use the chemical energy to do work and create change.

This is why living beings are able to do stuff.

We don't know when or how exactly the first ATP molecule was made on earth.

But every living thing we know uses ATP, or something very similar, to keep its internal machinery running.

Plants, fungi, bacteria, and animals need to survive.

While breaking down chemicals for energy is nice and all,

early life did miss out on the greatest available source of energy:

The Sun merges atoms and radiates photons away that carry energy into the solar system.

After hundreds of millions of years of evolution, finally, a cell figured out how to eat the Sun.

It absorbed radiation and converted much of it into neat little chemical packages that it could use to stay alive.

You take photons that are wobbly with electromagnetic energy,

and use a part of this energy to merge and combine different molecules together.

The electromagnetic energy is converted into chemical energy stored in the ATP molecule.

This process became even better, as some cells learned to create better chemical packages:

Easy to break down, high in energy, and pretty tasty.

This is so convenient, that some cells decided that instead of doing all that pesky photosynthesis work themselves,

they would just swallow other cells that did, and take their glucose and ATP.

This is widely considered one of the biggest anime betrayals in evolutionary history.

Photosynthesizing cells could mostly harness energy at their surfaces,

which limited their maximum energy production,

which limited their evolutionary avenues somewhat.

Evolution did its thing, but overall things stayed pretty much the same for hundreds of millions of years.

Until, one day, a cell ate another, and did not kill it.

Nothing had changed that day, but Earth would be different forever.

This cell became the ancestor of all animals on this planet.

Pink fairy armadillos, and Sunda colugos.

All can trace back their existence to this moment.

The merging of two living beings is so important,

because when those two cells became one, they became way more powerful.

The formerly independent cell in the inside, could stop trying to survive.

It could concentrate on one thing: make ATP.

It became the powerhouse of the cell: the first mitochondria.

The host cell's job became to ensure survival in the dangerous world,

Mitochondria basically reverse photosynthesis, in a similarly complex process.

They take sugar molecules that we got from eating other living things,

combust them with oxygen and precursor molecules, to make new, energy-rich ATP molecules.

This process works like a tiny furnace and spits out waste products like CO2,

water, and a little bit of kinetic energy that you experience as body heat.

This first division of labor, meant the new cell had way more energy available than any cell before,

which meant more possibilities for evolution to enable more complex cells.

At some point, these cells began to form small groups or communities,

which lead to multicellular life, and finally, to you.

Today, you are a pile of trillions of cells, each filled with dozens,

if not hundreds of little machines that provides you with usable energy to stay alive.

If this process is interrupted, even for a few minutes, you die.

(Teaser of Kurzgesagt: Science War, coming in 2021.)

But if life is so fragile, wouldn't it be a good idea to store ATP, like we store sugar in our fat cells,