Name: 植物の細胞。クラッシュコース生物学 #6 (Plant Cells: Crash Course Biology #6)
Uploaded: 2021-01-14T04:46:59.000Z
Duration: 10 min 28 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：

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Plants are freaking great because they have this magical wizard power that allows

them to take carbon dioxide out of the air and convert it into wonderful, fresh, pure,

They're also way cooler than us because, unlike us and every other animal on the planet,

they don't require all kinds of Hot Pockets and fancy coffee drinks to keep them going

The only thing plants need to make themselves a delicious feast is sunlight and water. Just

Paula Deen can't do that and she makes fried-egg bacon donut burgers.

I'm telling you this is surprisingly good.

But you know, part of this is plants! And everything in it, in fact, everything that is in this McDonalds

in fact, everything that you have ever eaten in your life is either made from plants, or

Plants probably evolved more than 500 million years ago. The earliest land-plant fossils

date back more than 400 million years ago. These plants were lycophytes which are still

around today and which reproduce through making a bunch of spores, shedding them, saying a

couple of Hail Marys and hoping for the best.

Some of these lycophytes went on to evolve into "scale trees," which are now extinct,

but huge, swampy forests of them used to cover the Earth.

Some people call these scale tree forests "coal forests" because there were

so many of them and they were so dense and they covered the whole Earth

and they eventually fossilized into giant seams of coal, which are very important to

So this is now called the Carboniferous Period.

See what they did there? Because Coal is made out of carbon, so they named the epoch of

geological history over how face-meltingly intense and productive these

I would give my left eyeball, three fingers on my left hand -- the middle ones,

so that I could hang loose -- and my pinky toe if I were able to go back and see these

scale forests because they were freaking awesome.

Anyway, Angiosperms, or plants that use flowers to reproduce, didn't develop until the end

of the Cretaceous Period, about 65 million years ago, just as the dinosaurs were

Which makes you wonder if in fact the first angiosperms assassinated all the dinosaurs.

I'm not saying that's definitely what happened, I'm just saying it's a little bit

Anyway, on the cellular level, plant and animal cells are actually pretty similar. They're

called eukaryotic cells, which means they have a "good

kernel." And that "kernel" is the nucleus. Not "new-cue-lus." And the nucleus can

You know, basically all of the popular kids.

Eukaryotic cells are way more advanced than prokaryotic cells. We have the eukaryotic

Prokaryotic basically means "before the kernel." Pro-kernel.

And then we have eukaryotic, which means "good kernel!"

The prokaryotes include your bacteria and your archaea, which you've probably met

before in your lifetime, every time you've had strep throat, for example, or if you've

ever been in a hot spring or an oil well or something. They're everywhere. They covered

But like I said, eukaryotes have that separately enclosed nucleus. That all important nucleus

that contains its DNA and is enclosed by a separate membrane

Because the eukaryotic cell is a busy place -- there's chemical reactions going on in

all different parts of the cell -- it's important to keep those places divided up.

Eukaryotic cells also have these little stuff-doing factories called organelles. I guess we decided

we would name everything something weird...

But, organelles. And they're suspended in cytoplasm, continuing with the

really esoteric terminology that you're going to have to know.

Cytoplasm is mostly just water, but it's some other stuff too. Well basically if you want

to know about the structure of the eukaryotic cell you should watch my video on animal cells.

Plant and animal cells are very similar environments. They control themselves in very similar ways,

but obviously, plants and animals are very different things.

What are the differences in a plant cell that makes it so different from an animal?

Well that's what we're going to go over now.

First, plants are thought to have evolved from green algae, which evolved from some

more primitive prokaryotes, and something plants inherited from their ancestors was

a rigid wall surrounding the plasma membrane of each cell.

So, this cell wall of plants is mainly made of cellulose and lignin, which are two really

Cellulose is by far the most common and easy to find complex

carbohydrate in nature, although if you were to include simple carbohydrates as well, glucose

And this is because, fascinating fact: cellulose is just a chain of glucose molecules!

If you want to jog your memory about carbohydrates and other

organic molecules, you can watch this episode right here.

Anyway, as it happens, you know who needs carbohydrates to live? Animals. But you know

what's a real pain in the ass to digest? Cellulose. Plants weren't born yesterday.

Cellulose is a far more complex structure than you will generally find in a prokaryotic cell,

but it's also one of the main things that differentiates a plant cell from an animal cell.

Animals cells don't have this rigid cell wall--they have just a flexible membrane that

frees them up to move around and eat plants and stuff. However, the cell wall gives

structure to a plant's leaves, roots and stems, and it also protects it to a degree.

Which is why trees aren't squishy and don't giggle when you poke them.

The combination of lignin and cellulose is what makes trees, for example,

able to grow really, really freaking tall.

Both of these compounds are extremely strong and resistant to deterioration.

When we eat food, lignin and cellulose is what we call "roughage" because we can't

digest it. It's still useful for us in certain aspects of our digestive system, but it's

Which is why eating a stick is really unappetizing.

And like, your shirt. This is a 100% plant shirt, but it doesn't taste good.

We can't go around eating wood like a beaver or grass like a cow because our digestive

However, other animals that don't have access to delicious donut burgers

have either developed gigantic stomachs like sloths or multiple stomachs like goats in

These animals have a kind of bacteria in their stomach that actually does the digestion of