Name: 生体分子 - あなたはあなたが食べるものです。クラッシュコース生物学 #3 (Biological Molecules - You Are What You Eat: Crash Course Biology #3)
Uploaded: 2021-01-14T04:20:40.000Z
Duration: 14 min 9 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

Hello, and welcome to the kitchen. I wanted to invite you here today because last week

we started off in my bathroom and kinda feel bad about that. And also because

as I'm making lunch today I wanted to sort of use it as a lab. During this time in my

kitchen I'm going to talk to you about three different things:

1) the three most important molecules on the Earth

2) possibly the grossest sandwich I'm ever going to eat

3) an obscure scientist who taught us almost everything we know about urine.

So far we've talked about carbon and we've talked about water, and now we're going

to talk about the molecules that make up every living thing

and every living thing in every living thing. I don't care if you're a bacterium or

a blue whale or if you're Lady Gaga, of if you're a mite living on the Queen of England's eyelashes.

They're called biological molecules. These aren't just building blocks, these are the

molecules necessary for every living thing on Earth to survive. They are essential sources

of energy. They are the means of storing that energy. They are also the instructions that

all organisms use to be born and grow and to ultimately pass those same instructions

And we call them: the carbohydrates, the lipids, the proteins, and the nucleic acids.

Today we're going to be talking about the first three. It's no coincidence that we

classify them in the same way that we classify food, because they're food. [Hank so smart!]

And for this classification, we have to thank a little-known English physician who hundreds

of years ago dedicated his life to the study of human pee.

That must mean that it's time for the most awkwardly named segment here on crash course:

His name was William Prout. In the early 1800s, he became fascinated with human digestion

especially our urine. That's because he thought the best way to understand the

human body was through chemistry, and the best way to understand body's chemistry was

to understand what it does with food. By day he was a practicing physician, but every morning

before breakfast he did research in his home laboratory in London. And there he did many

great things. Like, being the first to discover that our stomachs contained hydrochloric acid.

And writing a breakthrough book about kidney stones called

An Inquiry Into the Nature and Treatment of Gravel, Calculus, and Other Diseases Connected

with a Deranged Operation of the Urinary Organs.

And he was, of course, the first person to discover the chemical composition of pure

For the record, here it is: CO(NH2)2. And in the presence of water, urea gives off ammonia,

Through his years of studying urine, Prout came to the conclusion that all "foodstuffs"

fell into three categories: the saccharinous (carbohydrates), oleaginous (fats), and albuminous

(proteins). Indeed, he went so far as to say that in order to be healthy, you needed to

eat all three of these things and not just sheep kidneys and gin, which is what most

But like many great minds, Prout was overlooked in his own lifetime, because while he was

studying actual science, everyone else was walking around believing that the color of

your urine was determined by your personality.

And if you can tell that much by color I wonder what you could tell by taste.

Now he isn't understand that there were biological molecules

He didn't understand what these things were, but he did understand that there were three

ingredients necessary for life. And it turns out that all organisms either need to synthesize

or ingest those ingredients in order to live.

We're going to start out with the most basic of these ingredients for life: Carbohydrates.

You've no doubt heard of them. You may, in fact, be avoiding them like the plague.

But fact is that nothing, and no one, can avoid carbohydrates, because they are the

source of all energy that we have available to us.

Carbohydrates are made up of sugars, and the simplest of them are monosaccharides. Mono

for one, and saccharides for the actual root of the word sugar. The star of the show here

is glucose, because it's truly fundamental, by which I mean like Number One on the global

food chain. Because it comes from the sun.

All biological energy is originally captured from the sun by plants as glucose through

photosynthesis. And every cell that needs energy uses glucose to get that energy through

In addition to glucose there are other monosaccharides, like fructose, which has the same molecular

formula (C6H12O6), but arranged differently. These subtle chemical difference do matter.

Fructose, for example, is significantly sweeter than glucose. It's also processed by our bodies

And then there are disaccharides which -- like the name says -- are just two monosaccharides

put together. The most famous of these is sucrose, which is simply a glucose molecule

and a fructose molecule joined by a covalent bond.

Mono- and disaccharides are pretty much little niblets of energy that are really easy for

our body to process, but when these carbohydrates start to form into longer and longer chains,

their function and their roles change as well. Instead of being sources for instant energy,

they become storehouses of energy or structural compounds.

These are the polysaccharides. Instead of being just two or three monosaccharides put

together, polysaccharides can contain thousands of simple sugar units.

And because they're so big and burly, they're great for building with. In plants, cellulose

is the most common structural compound. It's just a bunch of glucose molecules bound together

and it is the most common organic compound on the planet.

Unfortunately, it's very difficult to digest. Cows can do it, but humans certainly cannot,

which is why you don't enjoy eating grass.

Polysaccharides are also really good for storing energy and not just structurally but just

as an energy store. And that's where we get bread. Now, really interesting thing here:

Bread is made up of starch, the most simple of which is called amylose. Amylose and cellulose

looks almost exactly identical, but one is grass and the other is bread.

Plants store glucose in the form of starch, and it comes in lots and lots of different

forms, from roots and tubers to the sweet flesh of fruits, to the starchy seeds of the

wheat plant that end up being milled into flour.

Ground-up grain is the main ingredient in the bread, of course, most of the calories,

or energy content, comes from carbohydrates. When I eat this -- and I am going to eat the

hell out of it -- I'm going to be eating all of the chemical energy that this wheat

plant got from the sun in order to feed it's next generation of seeds that we then stole

Now we, as human beings, can't grow fruits or tubers, so we have to store our energy

in a couple of different ways. The way that we tend to store carbohydrate energy is in

glycogen, which is very similar to amylose or starch, but has more branches and is more

complicated. It's basically made up of the glucose we have left over after we eat and

it sits in our muscles where it's ready to be used and it's also stored in our livers.

It's generally a pretty short term store. If we don't eat for a day pretty much all