This week, I'm actually on vacation in Hawaii,
hopefully shooting some Hello Science stuff too,
if I got the film permit.
We don't know at the point that I'm actually
recording this video.
So anyway, they're really hard to get
and I'm getting it for you.
But here's a short for Uno Dos of Trace.
The largest cell in our bodies is the female ovum.
It's 20 times larger than the smallest
cell in the human body, a sperm cell.
Red blood cells are eight picometers,
while axons in the brain, they can be a meter long.
Cells come in so many different sizes.
So how do they know when to stop growing?
I have questions.
[MUSIC PLAYING]
Hello, everyone!
And welcome back to Uno Dos of Trace.
Thanks for watching my last video,
and thanks for watching my next video,
because you're definitely going to do that.
You're going to subscribe and click the little bell,
and get the notification, all of those things.
OK.
So cells range in size.
There's skin cells, and red blood cells, and brain cells,
and muscle cells, and they're all different sizes.
Have you ever thought about how the cell knows
what size it's supposed to be?
So when I asked myself this question, I was like,
oh, well, it's one of two things.
It's either coded into the DNA, or maybe, which is unlikely,
it's because the cell has to fill a specific space.
So for example, picture the skin.
All those cells are just crammed in there, right,
so it must either fill that space
or be programmed to be a certain size.
But that's not it.
It's more simple than that.
The riddle of cell size has been explored forever,
and there's all these different hypotheses.
But recently, MIT researchers think they figured it out.
They grew yeast cells to 10 times their normal size.
Now, the function of a cell is more or less random.
I mean, things are moving around in there and stuff,
and they have purposes, but it's a bunch of different compounds
and proteins and things that interact inside of the cell.
As a cell grows, it needs to create more cytoplasm,
but the structures that are creating the proteins,
for example, don't get any bigger, which means,
at some point, you have this perfectly functioning cell
at a specific size, where the structures
are creating enough proteins to create enough reactions so
that the cell is functioning normally.
What they noticed in this study was
as the cell would grow past its normal size,
the cytoplasm would get diluted.
It would have the same amount of stuff in it,
but there was just more cytoplasm.
Now, dilution normally wouldn't matter,
because the cells would split, build another set
of structures providing more proteins,
and then they would keep going.
But because the yeast cells were altered so they wouldn't split,
the diluted cytoplasm meant the cell
would slow down and actually go into senescence.
Senescence is a natural process.
A lot of cells have it happen.
As people age, our cells tend to grow a little bit,
because there's more senescent cells.
They're essentially zombie cells.
They don't split and they don't particularly perform very well,
but it's a cell and it works just fine,
it just doesn't work really great.
As the cell's cytoplasm gets diluted,
the lead researcher says, quote, "Chemical reactions
inside the cell occur more slowly, and at some threshold,
the concentrations of certain proteins
might never be reached."
So certain reactions would never happen,
because the concentrations are lower.
So this is what makes cells pick a size.
Think of it like a lawn sprinkler.
You know--
[MIMICKING SPRINKLER SOUND]
--the impact sprinkler.
Now imagine you need to water an entire lawn,
and normally, you just have a lawn that's
five meters by five meters.
At some point, if you have a lawn that's
10 meters by five meters, that sprinkler isn't going to do it.
The water won't reach there.
It's spread too thin.
It's the same with cells, but what a cell would do
is build another sprinkler.
Once you've added that second sprinkler, you're good to go,
your whole lawn is watered and alive.
And this bears out in reality too.
Researchers added a second set of chromosomes
to some altered cells, and they grew twice as large
as normal, because they had more factories
to produce more proteins to get more reactions.
So the chemical reactions that make the cell live
are what determines the size of our cells.
Neat.
Thanks for watching Uno Dos of Trace.
Again, more Hello Science is coming soon.
Thanks again for watching.
Thanks.