By YouTube Originals
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In part two of our biology lesson with Ken Jeong, we’ll review the molecular biology of cellular respiration.
Transcript provided by YouTube:
00:02
( music playing )
00:04
How are you today?
00:05
♪ Celebrity ♪
00:06
Hi, I’m Ken Jeong,
00:09
and I’m your “Celebrity Substitute.”
00:13
Hi. My name’s Hannah Healey,
00:14
and I am a Biology teacher in Crystal River, Florida.
00:18
How could your food uncook itself? Hmm.
00:21
As a Biology teacher,
00:22
I think a lot about transformations.
00:24
But to explain how a cooked meal could magically uncook itself,
00:28
you’re going to need to understand
00:29
cellular respiration.
00:31
And because teaching from home can be really hard,
00:34
I am so glad to have a celebrity substitute to teach today’s lesson.
00:38
We already taught one great class together,
00:41
and I’m looking forward to welcoming back
00:43
comedian Ken Jeong.
00:45
– Hi, Hannah. – Hey, Ken. How are you today?
00:48
Thank you so much for having me again.
00:50
I mean, that previous lesson was so much fun.
00:53
For sure. I think the kids are really gonna have
00:55
a better understanding of the digestive system.
00:57
And they saw a celebrity eat a cookie.
01:00
Both very important educational tools, so…
01:04
– Uh… – …you’re welcome.
01:07
– Yeah. – Yeah, I know.
01:10
We just talked you through
01:11
how the digestive system functions.
01:13
To understand that, check out my lesson
01:16
about the human body systems.
01:17
Now, how exactly does the process of digestion work
01:21
on a micro level?
01:23
And the answer is cellular respiration,
01:27
so let’s get into it.
01:28
We all know that the point of eating is to power our body.
01:32
But what do our bodies do to the food
01:35
in order to get the energy from it?
01:37
How does food get broken down into the power your body needs?
01:41
Actually, Hannah,
01:42
could you grab those two bowls of oatmeal?
01:45
I don’t have any here ’cause I don’t eat healthy.
01:47
When you chew food, you break it down into a mush,
01:51
kind of like the bowl of oatmeal that Hannah has in front of her.
01:54
Then digestive enzymes break it down even further
01:59
into its component pieces.
02:01
Earlier today, Hannah mixed some digestive enzymes,
02:05
the same molecules that help process food in your stomach,
02:08
into one of those oatmeal bowls.
02:10
And this is what’s happening inside you.
02:14
So as you can see, without the enzymes,
02:17
the one bowl of oatmeal stayed whole.
02:19
But in the bowl with the enzymes,
02:21
they broke it back down into water and oats.
02:25
– Ta-da. – ( fanfare )
02:28
But at this point,
02:30
your body isn’t done uncooking your food yet.
02:33
A similar process has to happen at the molecular level,
02:37
breaking down bigger molecules into smaller pieces
02:41
and releasing the chemical energy your body can use
02:43
to power its cells.
02:45
And that process that we’re about to discuss
02:48
is called cellular respiration.
02:52
– ( bell ringing ) – Oh, so you know what that bell means?
02:54
That means it’s time to take a look at our newest student
02:57
in the Gif’ed And Talented Program– you!
03:01
( cheers and applause )
03:04
I’m sorry. I’m so– I’m just so honored.
03:07
I, uh– whoo!
03:10
Ahh.
03:11
I’m so sorry. I just thank you so much.
03:13
I just– a lot of people look at me online
03:17
and they’re like, “He’s Gif’ed.”
03:19
And I’m like, “Duh-doi.”
03:21
And then they’re just like, “What about my talent?”
03:23
You don’t see any of my talents in a gif.
03:26
– You are talented. – I guess I’m expelling my own energy right now,
03:30
which is cellular respiration.
03:34
Dig it.
03:39
( snorts )
03:40
Okay, so you’ve chewed up
03:41
and eaten your food.
03:42
The enzymes in your stomach have broken it down
03:45
the same way we watched them dissolve that bowl of oatmeal.
03:48
But we’re still left with sugar molecules,
03:50
glucose to be precise,
03:52
that are too big for your body to use as fuel,
03:55
and they’ve got to be uncooked ever further.
03:58
And that– so sorry.
04:00
I think my kids are playing piano.
04:02
– Oh, wow. They’re killing it. – ( piano playing )
04:04
I’m just gonna text my kids right now.
04:10
And that is where cellular respiration comes in
04:13
because cellular respiration
04:14
converts glucose into energy.
04:17
And that is how every living thing on the planet stays alive.
04:20
You’re doing cellular respiration right now.
04:23
So is the dog down the street
04:25
and the bacteria on the bottom of your shoes.
04:27
In cellular respiration, we start out with one of those
04:30
big glucose molecules and use oxygen,
04:34
and we end up with carbon dioxide, water,
04:37
and the energy your cells use
04:39
to do literally everything that keeps you alive.
04:42
And to show you what that process looks like
04:44
while I explain how cellular respiration works,
04:47
Hannah’s going to get some yeast,
04:49
doing cellular respiration right in front of us.
04:52
I’ve got three bottles here
04:54
filled with yeast and water inside.
04:56
I’m actually gonna be placing sugar in two of them.
04:59
A lot of sugar in this first bottle.
05:03
Just a little bit in this one.
05:06
And then this third one is our control,
05:08
so we won’t be adding any sugar to him.
05:11
But because you can’t have
05:12
cellular respiration without sugar,
05:14
only these two bottles will actually have
05:16
cellular respiration occurring.
05:17
So by the time I’m finished
05:19
explaining the steps of cellular respiration,
05:22
those two balloons are going to be inflated
05:24
full of carbon dioxide,
05:26
and that’s how we’ll know
05:27
cellular respiration has occurred.
05:30
So how does cellular respiration
05:31
help us uncook a sugar into even smaller parts?
05:34
And how is that going to produce the carbon dioxide
05:37
that’s going to magically inflate those balloons?
05:39
To understand that, let’s get deep into the stages
05:42
of cellular respiration.
05:44
Cellular respiration is made up of glycolysis,
05:48
the Krebs cycle,
05:49
and the electron transport chain.
05:52
And anyone who knows me knows I love a good mnemonic,
05:57
so I remember the cellular respiration stages by the phrase,
06:00
“Good! Ken Can Eat That Cookie.”
06:03
And it’s true, I can,
06:06
because I know my body’s going to run
06:08
cellular respiration.
06:10
Okay, so let’s just say I was good
06:11
and I did eat that cookie.
06:13
Well, my body breaks it down into its parts,
06:16
and I’m left with some molecules of glucose.
06:19
For cellular respiration,
06:21
we’ve got glucose from that cookie I ate
06:23
and some oxygen that I breathe,
06:25
and they’re going to enter stage one
06:27
of cellular respiration– glycolysis.
06:31
In glycolysis,
06:32
a single glucose molecule from my cookie
06:35
is split apart into two smaller molecules,
06:38
and in the process, two ATP are released.
06:42
ATP, or adenosine triphosphate,
06:46
is the whole point of all of this.
06:48
It’s the point of eating,
06:49
it’s the point of cellular respiration.
06:51
It is chemical energy
06:53
broken down small enough
06:55
that your cells can actually use it.
06:57
So we’re trying to make as much of this as we can,
07:00
and so far, we’re got two.
07:02
At the end of stage one,
07:04
we’ve released two ATP
07:06
and our glucose has been broken down
07:08
into two even smaller molecules.
07:12
So far, all the action has been taking place
07:14
in a part of the cell called the cytoplasm.
07:17
That’s basically the goo of the cell.
07:19
Stages two and three,
07:21
the whole rest of the cellular respiration process,
07:23
are going to take place inside the mitochondria.
07:26
And that’s why they’re called the powerhouses,
07:28
because we’re about to unlock a whole lot more ATP.
07:32
We’re about to enter stage two, the Krebs cycle,
07:36
or in my mnemonic, “Ken Can.”
07:38
There you go.
07:39
By the time we get to the Krebs cycle,
07:42
the glucose from our cookie has already been split apart
07:45
and then oxidized into acetyl-CoA.
07:48
At every step of the way,
07:50
we’re trying to break down
07:51
into smaller and smaller molecules
07:53
and release energy that your cells can use.
07:56
Acetyl-CoA is smaller than glucose,
07:59
and I bet you can predict what’s gonna happen next.
08:02
That’s right.
08:03
Acetyl-CoA is going to get
08:05
broken down even smaller,
08:07
and in the process, we create two more ATP.
08:12
Now, we reach the third
08:14
and final stage of cellular respiration,
08:17
the boss level,
08:19
the electron transport chain.
08:22
Or, going back to my mnemonic,
08:23
we’re now at “Eat That Cookie!”
08:26
And you have to say it just like that.
08:27
This is where all the rest
08:28
of the energy is cashed in.
08:30
Using an enzyme called ATP synthase
08:33
to speed things along,
08:34
the electron transport chain starts raining ATP.
08:38
We can make as many as 32 molecules of ATP
08:42
during the electron transport chain.
08:44
And that’s where we started.
08:45
With the one molecule of glucose from my cookie,
08:48
now we’re left with 36 ATPs worth of energy
08:51
for my cells to use, along with some water
08:54
and some carbon dioxide for me to exhale.
08:57
And exhaling carbon dioxide
09:00
is exactly what our single-celled friends the yeast
09:03
have been doing this whole time
09:05
in the bottles Hannah has set up.
09:08
So let’s go back and check in with them.
09:10
Hannah, what’s been happening?
09:12
Ken, check this out. This is incredible.
09:15
Wow, look at that.
09:17
In the bottles with sugar,
09:18
the yeast went to town and used cellular respiration
09:21
to break it down into water and carbon dioxide,
09:24
which is what’s filling the balloons–
09:26
more sugar, more cellular respiration,
09:30
more carbon dioxide, and a bigger balloon.
09:33
No sugar, no respiration, no balloon inflation.
09:36
So, how can your food uncook itself?
09:40
Cooking, if you think about it,
09:41
it’s the art of putting together ingredients
09:43
and making something complex.
09:45
Digestion is taking that complex meal
09:47
and breaking it down
09:48
into its simplest component parts.
09:50
Your body uses enzymes and cellular respiration
09:54
to break food back down into its basic building blocks
09:58
and unleash ATP.
10:00
And along the way,
10:01
it releases water and carbon dioxide,
10:04
which allowed our balloons to inflate themselves.
10:08
So I hope you’ve enjoyed this demonstration
10:10
Hannah has set up using yeast
10:13
and showing cellular respiration.
10:15
I hope I wasn’t too talkative.
10:17
I don’t want to leave you deflated.
10:20
( balloon deflating )
10:23
Deflated. I’m sorry, guys.
10:27
There’s nothing more I can do with that joke.
10:29
That joke was the no sugar joke.
10:31
That was the control.
10:33
So, Hannah, if you didn’t laugh,
10:36
that was the point.
10:37
Science. Dig it.
10:38
Respiration. Gas.
10:42
YouTube Learning.
10:44
Class is over, and you did great.
10:46
You want to get some extra credit?
10:48
Hit the subscribe button so you’ll never miss
10:50
a “Celebrity Substitute” lesson right here on YouTube.
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Photo credit: Screenshot from video