Have you ever wondered what you're really made of?
The building blocks that your body is built from.
Maybe you've heard the phrase "carbon-based life -form"?
We're carbon-based, right?
So, does that mean we have more carbon in us than anything else?
Actually no... let's take a closer look.
This is an atom.
Nope, sorry... I can't believe I screwed this up already... let's try again.
This is an illustration of an atom.
An atom is the smallest thing in the universe and can't be divided into smaller parts.
Okay, that's not strictly true.
But! For our purposes it is helpful to think of an atom as a tiny, tiny, single unit (for now)
represented as a solid sphere.
You are made of about 7 billion billion billion atoms
Give or take
Or per kilogram of human, it's about this many atoms; you could do the math for your body.
Atoms come in more than one flavor though, about a hundred kinds.
We call these different types "elements", and you'll see them laid out all nicely on the Periodic Table.
Happy Anniversary, by the way.
Broadly speaking, they're arranged from small and light elements to big and heavy elements.
We're curious about the elements that we're constructed from, so let's highlight a few of these.
As quote "carbon-based life-forms", I guess we should start with this one.
This is Carbon.
Let's give it a color, to help us identify it.
How about dark grey, because...
And this one, right next to Carbon is Nitrogen.
Let's make it blue because...
And this one is Oxygen (you might have heard of it). We'll make it red, because...
And Hydrogen, the smallest element, we'll make white because... it's invisible?
Let's collect a few more.
Phosphorus
Sulfur
Chlorine, and Iodine
And let's add some metals to our collection
Sodium, Magnesium, Potassium, Calcium
Calcium, is that a metal? I guess technically it must be.
Iron, Copper, and finally Zinc
Those ones sound a bit more metallic.
So, a reminder: what do these specific kinds of atoms have in common?
You!
Human beings, and in fact all life on earth like trees, fish, mushrooms, dogs, bacteria
are made up of basically just these elements.
It's not an even mix though, not by a long shot.
By weight, you're almost entirely Oxygen, Carbon, and Hydrogen
with a little Nitrogen, a dash of Calcium, Phosphorus and Sulfur
a smidge of Potassium, Sodium, Chlorine, and Magnesium, and basically nothing of everything else.
Notice here that Carbon is neither top of the chart by mass nor by number of atoms.
We'll come back to that.
Now surely, you're not just a sack of all these atoms loosely jumbled together? Are you?
Well no, of course not. You have a lot more structure.
Atoms can link together to form... molecules!
What is a molecule?
I just told you, atoms stuck together.
Stuck together how?
With bonds.
I still don't want to break apart our nice little atoms so we won't get into exactly how bonds form.
Usually you'll see them represented in images as little sticks between the spheres.
And we shrink the atoms down smaller than they really are just so we can see these sticks.
It's helpful to understand that bonds aren't physical things separate from atoms
we just draw them that way.
Sometimes atoms don't just form a single bond, they can form double or even triple bonds.
The sticks help us notice that, see?
On paper, we can draw the atoms and bonds like this.
Now that we know atoms can combine to form molecules, what kinds of molecules are we built from?
There better be some carbon.
Well to start, there's several important molecules that are made up of just two or three atoms.
You don't breathe this kind of oxygen, you breathe this kind of oxygen.
Neat!
And carbon dioxide, which your body produces and then you need to breathe it out.
Notice the double bonds here?
Oh! Carbon! Carbon dioxide, maybe that's why carbon-based... No... no, that's not it...
Well anyway, let's look at water.
Good old H2O.
Oh yeah, by the way, this angle?
It turns out that when there's three or more atoms linked together
they connect at specific angles, sometimes straight, sometimes with a bend.
This bend in the water molecule is really really incredibly important! Critical!
I don't think it's overstating my case to say that without this bend...
there's no life on earth, at all, ever. Period.
Also... you are about 50-70% this molecule.
Hang on, hang on, if we're more than half water
which last I checked, does not have any carbon in it, then how can we be called carbon-based life-forms?
Well, carbon is a pretty special element.
A single carbon atom forms four bonds with other atoms, making it incredibly versatile.
Sometimes that's two double bonds
or a triple and a single
or four single bonds to four other atoms
or one double and two singles
It turns out that the overwhelming majority of the kinds of molecules in your body include carbon.
We call molecules made by living things "biomolecules", and like I said carbon features prominently in almost all of them.
Carbon helps make up small biomolecules like vitamins
hormones
nutrients like sugars and fats
and forms the literal backbone of bigger molecules and bigger molecules and even bigger molecules
Oh and even bigger molecules.
These biomolecules are extremely diverse
There are thousands upon thousands of different kinds, and in my opinion, they're all amazing.
We'll be exploring many of these in future videos.
But why carbon though? Why not another element?
I think there's several reasons.
I mentioned its geometry: the four bonds and specific angles
that allow for a crazy number of combinations of atoms and structural arrangements.
Secondly, carbon is plentiful in the universe and on earth.
Next, if we look at related elements, around carbon on the Periodic Table
typically these form only three or two or even one stable bond
so they can't be used in as many different kinds of structures.
Silicon does form four bonds and it is plentiful on earth
but it is a larger atom than carbon, and so silicon to silicon bonds aren't as stable.
In contrast, carbon-carbon bonds are very strong
as evidenced by diamond, which is pure carbon
But importantly, carbon bonds in biomolecules can be broken
and formed through chemical reactions in our body.
Carbon is a unique element, and in every example we know of
it is the stable, versatile, reactive, basis for life.
Thank you so much for watching, carbon-based, water-logged human.
I hope you'll consider subscribing to watch more biology animations
and maybe sharing it with other curious carbon creatures.
I'm Stuart, and this is Biocinematics.