( music playing )
How are you today?
♪ Celebrity ♪
Hi, I'm Ken Jeong,
and I'm your "Celebrity Substitute."
Hi. My name's Hannah Healey,
and I am a Biology teacher in Crystal River, Florida.
How could your food uncook itself? Hmm.
As a Biology teacher,
I think a lot about transformations.
But to explain how a cooked meal could magically uncook itself,
you're going to need to understand
cellular respiration.
And because teaching from home can be really hard,
I am so glad to have a celebrity substitute to teach today's lesson.
We already taught one great class together,
and I'm looking forward to welcoming back
comedian Ken Jeong.
- Hi, Hannah. - Hey, Ken. How are you today?
Thank you so much for having me again.
I mean, that previous lesson was so much fun.
For sure. I think the kids are really gonna have
a better understanding of the digestive system.
And they saw a celebrity eat a cookie.
Both very important educational tools, so...
- Uh... - ...you're welcome.
- Yeah. - Yeah, I know.
We just talked you through
how the digestive system functions.
To understand that, check out my lesson
about the human body systems.
Now, how exactly does the process of digestion work
on a micro level?
And the answer is cellular respiration,
so let's get into it.
We all know that the point of eating is to power our body.
But what do our bodies do to the food
in order to get the energy from it?
How does food get broken down into the power your body needs?
Actually, Hannah,
could you grab those two bowls of oatmeal?
I don't have any here 'cause I don't eat healthy.
When you chew food, you break it down into a mush,
kind of like the bowl of oatmeal that Hannah has in front of her.
Then digestive enzymes break it down even further
into its component pieces.
Earlier today, Hannah mixed some digestive enzymes,
the same molecules that help process food in your stomach,
into one of those oatmeal bowls.
And this is what's happening inside you.
So as you can see, without the enzymes,
the one bowl of oatmeal stayed whole.
But in the bowl with the enzymes,
they broke it back down into water and oats.
- Ta-da. -
But at this point,
your body isn't done uncooking your food yet.
A similar process has to happen at the molecular level,
breaking down bigger molecules into smaller pieces
and releasing the chemical energy your body can use
to power its cells.
And that process that we're about to discuss
is called cellular respiration.
-
That means it's time to take a look at our newest student
in the Gif'ed And Talented Program-- you!
( cheers and applause )
I'm sorry. I'm so-- I'm just so honored.
I, uh-- whoo!
Ahh.
I'm so sorry. I just thank you so much.
I just-- a lot of people look at me online
and they're like, "He's Gif'ed."
And I'm like, "Duh-doi."
And then they're just like, "What about my talent?"
You don't see any of my talents in a gif.
- You are talented. - I guess I'm expelling my own energy right now,
which is cellular respiration.
Dig it.
( snorts )
Okay, so you've chewed up
and eaten your food.
The enzymes in your stomach have broken it down
the same way we watched them dissolve that bowl of oatmeal.
But we're still left with sugar molecules,
glucose to be precise,
that are too big for your body to use as fuel,
and they've got to be uncooked ever further.
And that-- so sorry.
I think my kids are playing piano.
- Oh, wow. They're killing it. - ( piano playing )
I'm just gonna text my kids right now.
And that is where cellular respiration comes in
because cellular respiration
converts glucose into energy.
And that is how every living thing on the planet stays alive.
You're doing cellular respiration right now.
So is the dog down the street
and the bacteria on the bottom of your shoes.
In cellular respiration, we start out with one of those
big glucose molecules and use oxygen,
and we end up with carbon dioxide, water,
and the energy your cells use
to do literally everything that keeps you alive.
And to show you what that process looks like
while I explain how cellular respiration works,
Hannah's going to get some yeast,
doing cellular respiration right in front of us.
I've got three bottles here
filled with yeast and water inside.
I'm actually gonna be placing sugar in two of them.
A lot of sugar in this first bottle.
Just a little bit in this one.
And then this third one is our control,
so we won't be adding any sugar to him.
But because you can't have
cellular respiration without sugar,
only these two bottles will actually have
cellular respiration occurring.
So by the time I'm finished
explaining the steps of cellular respiration,
those two balloons are going to be inflated
full of carbon dioxide,
and that's how we'll know
cellular respiration has occurred.
So how does cellular respiration
help us uncook a sugar into even smaller parts?
And how is that going to produce the carbon dioxide
that's going to magically inflate those balloons?
To understand that, let's get deep into the stages
of cellular respiration.
Cellular respiration is made up of glycolysis,
the Krebs cycle,
and the electron transport chain.
And anyone who knows me knows I love a good mnemonic,
so I remember the cellular respiration stages by the phrase,
"Good! Ken Can Eat That Cookie."
And it's true, I can,
because I know my body's going to run
cellular respiration.
Okay, so let's just say I was good
and I did eat that cookie.
Well, my body breaks it down into its parts,
and I'm left with some molecules of glucose.
For cellular respiration,
we've got glucose from that cookie I ate
and some oxygen that I breathe,
and they're going to enter stage one
of cellular respiration-- glycolysis.
In glycolysis,
a single glucose molecule from my cookie
is split apart into two smaller molecules,
and in the process, two ATP are released.
ATP, or adenosine triphosphate,
is the whole point of all of this.
It's the point of eating,
it's the point of cellular respiration.
It is chemical energy
broken down small enough
that your cells can actually use it.
So we're trying to make as much of this as we can,
and so far, we're got two.
At the end of stage one,
we've released two ATP
and our glucose has been broken down
into two even smaller molecules.
So far, all the action has been taking place
in a part of the cell called the cytoplasm.
That's basically the goo of the cell.
Stages two and three,
the whole rest of the cellular respiration process,
are going to take place inside the mitochondria.
And that's why they're called the powerhouses,
because we're about to unlock a whole lot more ATP.
We're about to enter stage two, the Krebs cycle,
or in my mnemonic, "Ken Can."
There you go.
By the time we get to the Krebs cycle,
the glucose from our cookie has already been split apart
and then oxidized into acetyl-CoA.
At every step of the way,
we're trying to break down
into smaller and smaller molecules
and release energy that your cells can use.
Acetyl-CoA is smaller than glucose,
and I bet you can predict what's gonna happen next.
That's right.
Acetyl-CoA is going to get
broken down even smaller,
and in the process, we create two more ATP.
Now, we reach the third
and final stage of cellular respiration,
the boss level,
the electron transport chain.
Or, going back to my mnemonic,
we're now at "Eat That Cookie!"
And you have to say it just like that.
This is where all the rest
of the energy is cashed in.
Using an enzyme called ATP synthase
to speed things along,
the electron transport chain starts raining ATP.
We can make as many as 32 molecules of ATP
during the electron transport chain.
And that's where we started.
With the one molecule of glucose from my cookie,
now we're left with 36 ATPs worth of energy
for my cells to use, along with some water
and some carbon dioxide for me to exhale.
And exhaling carbon dioxide
is exactly what our single-celled friends the yeast
have been doing this whole time
in the bottles Hannah has set up.
So let's go back and check in with them.
Hannah, what's been happening?
Ken, check this out. This is incredible.
Wow, look at that.
In the bottles with sugar,
the yeast went to town and used cellular respiration
to break it down into water and carbon dioxide,
which is what's filling the balloons--
more sugar, more cellular respiration,
more carbon dioxide, and a bigger balloon.
No sugar, no respiration, no balloon inflation.
So, how can your food uncook itself?
Cooking, if you think about it,
it's the art of putting together ingredients
and making something complex.
Digestion is taking that complex meal
and breaking it down
into its simplest component parts.
Your body uses enzymes and cellular respiration
to break food back down into its basic building blocks
and unleash ATP.
And along the way,
it releases water and carbon dioxide,
which allowed our balloons to inflate themselves.
So I hope you've enjoyed this demonstration
Hannah has set up using yeast
and showing cellular respiration.
I hope I wasn't too talkative.
I don't want to leave you deflated.
( balloon deflating )
Deflated. I'm sorry, guys.
There's nothing more I can do with that joke.
That joke was the no sugar joke.
That was the control.
So, Hannah, if you didn't laugh,
that was the point.
Science. Dig it.
Respiration. Gas.
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