Plant Cells: Crash Course Biology #6
Summary
TLDRこの動画脚本では、植物が持つ魔法のような力について語られています。植物は二酸化炭素を取り込んで酸素に変換し、日光と水だけで成長できるという驚くべき能力を持っている。さらに、植物細胞と動物細胞の違い、特に細胞壁と葉緑体の特徴について説明しています。植物は緑色のアルゲーが進化し、細胞壁を形成し、光合成を通じて自己完結的に成長する能力を持つようになった。このビデオでは、植物の細胞構造とその機能を簡単に理解できるように紹介しています。
Takeaways
- 🌿 植物は魔法のような力を持っており、空気中の二酸化炭素を取り込んで新鮮で純粋な酸素に変換することができる。
- 🌞 植物は動物とは異なり、日光と水以外には何も必要なく、自己完結して成長する。
- 🌱 植物は約5億年前から進化し、最も古い陸生植物の化石は4億年以上前のものがある。
- 🌲 炭鉱森は、地球上を覆う密な森林であり、その多くは石炭になり、私たちの生活に重要な役割を果たしている。
- 🌼 被子植物はcretaceous期の終わりに登場し、その時期に恐竜が絶滅したため、被子植物が恐竜を滅ぼしたのではないかと疑われる。
- 🔬 植物細胞と動物細胞は非常によく似ており、核を持つ真核細胞と呼ばれる。
- 🍃 植物細胞には細胞壁があり、セルロースとリンネンからできており、これにより植物は硬くなる。
- 🌱 植物は緑色の藻類から進化し、細胞膜を囲む堅い壁を遺伝した。
- 🌿 植物細胞には葉緑体があり、太陽からの光エネルギーを糖と酸素に変換する。
- 💧 植物細胞には中央大空胞があり、水や他の物質を保持し、細胞に構造的なサポートを提供する。
Q & A
植物が持っている魔法のような力は何ですか?
-植物は空気中の二酸化炭素を取り出して新鮮で純粋な酸素に変換する魔法のような力を持っています。
植物はどのようにしてエネルギーを得ますか?
-植物は太陽光と水があればエネルギーを得ることができます。これらは植物にとって十分な「食べ物」です。
植物はどの時代から進化し始めたと言われていますか?
-植物はおそらく5億年以上前に進化し始めたと言われています。
植物が最初に化石として確認されたのはいつ頃ですか?
-植物の最も古い陸上植物の化石は4億年以上前に確認されています。
炭素紀はどのような意味を持っていますか?
-炭素紀は、昔の森林が炭鉱に変わったため、炭素(炭の主成分)から名付けられた時代です。
被子植物はいつ頃発達しましたか?
-被子植物はcretaceous periodの終わり頃、約6500万年前に発達しました。
真核細胞と原核細胞の違いは何ですか?
-真核細胞は核を持ち、複雑な構造を持っていますが、原核細胞は核を持たず、単純な構造です。
植物細胞の特徴的な部分として、細胞壁は何からできていますか?
-植物細胞の細胞壁はセルロースとリンジンからできており、非常に強靭で耐久性があります。
動物細胞と植物細胞の違いは何ですか?
-植物細胞には細胞壁、葉緑体、大きな中心空胞などがありますが、動物細胞にはそれらの構造はなく、柔軟な膜のみがあります。
葉緑体は植物細胞でどのような役割を果たしますか?
-葉緑体は太陽からの光エネルギーを糖と酸素に変換し、植物が食べ物を作るためのエネルギー源となります。
植物細胞の大きな中心空胞は何の役割を果たしますか?
-植物細胞の大きな中心空胞は細胞内圧を維持し、細胞の形を保ち、必要な時に水や他の物質を蓄えるための貯蔵庫として機能します。
Outlines
🌿 植物の魔法
植物は空気中の二酸化炭素を取り込んで酸素に変換する魔法のような力を持っている。植物は他の動物とは異なり、特別な食べ物や飲み物を必要とせず、太陽光と水があれば十分である。植物は地球上の生命にとって非常に重要であり、私たちの食べ物はすべて植物から来ているか、植物を食べた動物から来ている。植物は5億年以上前に進化し、陸上の初期植物の化石は4億年以上前に遡る。初期の植物は現在も残るリコフェイと呼ばれるスポラを産生する植物で、彼らから進化した「スケールツリー」は現在は絶滅しているが、かつて地球を覆っていた。彼らは炭素を多く含んでおり、私たちの生活に重要なエネルギー源である石炭に貢献している。
🌳 植物細胞の構造と機能
植物細胞と動物細胞は非常によく似ており、両方とも真核細胞と呼ばれる高度な細胞である。真核細胞は核を持ち、細胞内の化学反応を管理する。植物細胞には細胞壁があり、セルロースとリンネンという強力な化合物からできており、植物には動物細胞にはないplastidsという器官がある。plastidsの中で最も重要なのは葉緑体で、太陽からの光エネルギーを糖と酸素に変換する。また、植物細胞には大きな中心空胞があり、細胞の構造を支え、水や他の化合物を蓄えるための貯蔵庫である。これらの特徴は植物が私たちの食事に必要な食べ物と肺に必要な空気を提供できるようにしている。
📚 植物細胞の基礎
このセクションでは、植物細胞の基礎について簡単に復習する。植物細胞には、非常に硬いセルロースからできた細胞壁がある。また、他の器官と分離された小さな袋に核が含まれており、plastidsと呼ばれる器官が光合成を行い、中心空胞は水や他の物を貯蔵し、細胞の構造をサポートする。これらのユニークな特徴が、植物が私たちのテーブルに食べ物を置いて肺に空気を提供できるようにしている。
Mindmap
Keywords
💡光合成
💡葉緑体
💡セルロース
💡リンゲン
💡真核細胞
💡細胞壁
💡中心空泡
💡原核細胞
💡プロトプラスマ
💡有機分子
Highlights
植物通过光合作用将二氧化碳转化为氧气,对人类至关重要。
植物不需要复杂的食物链,仅需阳光和水即可生存。
人类所食用的所有食物,无论是直接还是间接,都源自植物。
植物可能在超过5亿年前就已经演化出现。
最早的陆生植物化石可追溯至4亿多年前,属于石松类植物。
石松类植物通过产生孢子进行繁殖。
石松类植物演化成巨大的鳞木,这些森林最终形成了煤炭。
这一时期被称为石炭纪,因为煤炭的形成。
被子植物,使用花朵繁殖的植物,直到白垩纪末期才出现。
植物和动物细胞在细胞层面上非常相似,都拥有真核细胞。
真核细胞比原核细胞更高级,拥有独立的细胞核。
植物细胞继承了其祖先的细胞壁,主要由纤维素和木质素构成。
纤维素是自然界中最常见的复杂碳水化合物,由葡萄糖分子链组成。
植物细胞的细胞壁为其提供结构支持和一定程度的保护。
植物细胞中的叶绿体是进行光合作用,制造食物和氧气的器官。
植物细胞的大中央液泡有助于维持细胞结构并储存水分和其他物质。
植物细胞的独特特征使其能够为我们提供食物和氧气。
Transcripts
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,
oxygen for us to breathe.
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
sunlight and water!
Paula Deen can't do that and she makes fried-egg bacon donut burgers.
I'm telling you this is surprisingly good.
This is a different kind of magic.
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
from something that ate plants.
So, let's talk about plants!
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
our lifestyles today.
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
forests were.
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
dying out.
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
suspicious.
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
be found in all sorts of cells.
Animal cells, plant cells, algae cells.
You know, basically all of the popular kids.
Eukaryotic cells are way more advanced than prokaryotic cells. We have the eukaryotic
cell and we have the prokaryotic cell.
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
the planet. They cover you!
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.
Let's just link to it right here.
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
tough compounds.
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
would win that one.
And this is because, fascinating fact: cellulose is just a chain of glucose molecules!
You're welcome.
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
not nutritious.
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
systems just aren't set up for that.
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
order to make a living eating cellulose.
These animals have a kind of bacteria in their stomach that actually does the digestion of
the cellulose for it. It breaks the cellulose into individual glucose molecules, which can
then be used for food.
But other animals, like humans -- mostly carnivores -- don't have any of that kind of bacteria,
which is why it's so difficult for us to digest sticks.
Ah! But there is another reason why cellulose and lignin are very very useful to us as humans:
It burns, my friends!
This is basically what would happen in our stomachs. It's oxidizing. It's producing the
energy that we would get out of it if we were able to, except it's doing it very very quickly.
And this is the kind of energy, like, this energy that's coming out of it right now,
is the energy that would be useful to us if we were cows.
But we're not. So instead, we just use it to keep ourselves warm on the cold winter
nights.
Ow! It's on me! Ow! Ahh!
Anyway, while we animals are walking around, spending our lives searching for ever more
digestible plant materials, plants don't have to do any of that. They just sit there and
they make their own food. And you know how they do that? They do it with photosynthesis!
Another thing that plant cells have that animal cells just don't have are plastids, organelles
that plants use to make and store compounds that they need. And you wanna know something
super interesting about plastids?
They and their fellow organelles, the mitochondria that generate
energy for the cell, actually started as bacteria that were absorbed
into plant cells very early in their evolution
like maybe some protist-like cell absorbed a bacteria, and it found that instead of digesting
that bacteria for the energy that it has, it could use that bacteria. That bacteria
could create energy for the cell or convert light into lovely glucose compounds, which
is crazy!
Nobody's really, precisely sure how this happened, but they know that it did happen because plastids
and mitochondria both have double membranes. One from the original bacteria, and one from
the cell as it wrapped around it. Cool, huh?
Anyway, the most important of the plastids are chloroplasts, which convert light energy
from the sun into the sugar and into oxygen, which the plant doesn't need,
so it just gets rid of it.
All the green parts of a plant that you see -- the leaves, the non-woody
stems, the unripened oranges -- are all filled with cells which are filled with
chloroplasts, which are making food and oxygen for you.
You're very welcome, I'm sure.
Another big difference between a plant cell and an animal cell, is the large,
central vacuole. Plant cells can push water into vacuoles which provides turgor pressure
from inside the cell, which reinforces the already stiff cellulose wall
and makes the plant rigid like a crunchy piece of celery or something.
Usually when soil dries out or a celery stalk sits in your refrigerator for too long, the
cells lose some water, turgor pressure drops, and the plant wilts
or gets all floppy.
So, the vacuoles are also kind of a storage container for the cell. It can contain water,
which plants need to save up, just in case. And also other
compounds that the cell might need. It can also contain and export stuff the cell
doesn't need anymore, like wastes. Some animal cells also have vacuoles,
but they aren't as large and they don't have this very important job of giving the animal shape.
So now, let's do this. Let's just go over the basics of plant cell anatomy:
1. They've got a cell wall that's made out of cellulose and so it's really rigid
and not messing around.
2. They've got a nucleus in its own little baggie that's separate from all the other
organelles. This is basically the headquarters of any eukaryotic cell: it
stores all the genetic information for the plant and also acts as the cell's activities
director, telling it how to grow, when to split, when to jump and how high...that sort of thing.
Animal cells have this kind of nucleus too, but prokaryotes
don't. Which is why they're stuck hanging around in oil wells and stuff.
3. They've got plastids, including chloroplasts, which are awesome green food-making machines.
4. They've got a central vacuole that stores water and other stuff and helps give the cell
structural support.
And so, stack these cells on top of one another like apartments in
an apartment building
and you've got a plant!
And all of these unique features are what make it possible for plants to put food on
our table and air in our lungs. So next time you see a plant, just go ahead and shake its
hand and thank it for its hard work and its service.
Now, we went over that stuff pretty fast, so if you want to go back and listen to any
of it, we have a review section over here for stuff that you may not have totally picked
up on or just want to watch again.
It's not a huge piece of your life to re-watch some stuff so go ahead and click on these things.
If you have questions to do with plant cell anatomy, please leave them for us in the comments
and we will hopefully get to those.
You can also hook up with us on Facebook and Twitter of course and we will see you on episode
7 of Biology Crash Course.
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