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  • Hi. It's Mr. Andersen and in this video I'm going to talk about cells.

    嗨,我是Andersen先生,在這段視頻中,我將談論細胞。

  • Life is made of cells. It's the basic unit of structure and function. And also all cells

    生命是由細胞組成的。它'是結構和功能的基本組織、部門。也是所有細胞

  • we have must come from preexisting cells. And so how does that work? It's through a

    我們所擁有的一定是來自於現有的細胞。那麼這又是怎麼做到的呢?它是通過一個

  • process called cell division. This is going to occur in all cells, both prokaryotic like

    稱為細胞分裂的過程。這在所有細胞中都會發生,無論是原核細胞還是像

  • bacteria and eukaryotic like you. And through cell division one cell can become two. Which

    細菌和你這樣的真核生物。而通過細胞分裂,一個細胞可以變成兩個。哪種

  • can quickly become four and then eight and then sixteen. And so we get exponential growth

    可以很快變成4個,然後是8個,然後是16個。所以我們得到了指數級的增長

  • in cells. And to give you an idea how quickly this goes, you started life as one fertilized

    細胞中。為了讓你知道這一切有多快,你的生命是從一個受精開始的。

  • egg. Or one zygote. But those were quickly dividing over time. And it eventually created

    卵子。或者是一個胚胎。但隨著時間的推移,這些都在迅速分裂。最終形成了

  • an adult that's going to have around 10 trillion cells inside your body. And they all came

    一個成年人的體內會有大約10萬億個細胞。而他們都來了

  • from that original cell. Now to even increase that number quite a bit, just look in your

    從最初的細胞。現在,為了增加這個數字,只要看看你的

  • gut and we're going to find that the bacteria living in your digestive tract are going to

    腸道和我們'會發現,生活在你的消化道的細菌是要

  • outnumber the cells in your whole body ten to one. There are going to be 100 trillion

    比你全身的細胞數量多十倍。將會有100萬億

  • bacteria just living in your gut. And they're going to be outnumbered about 10 to one by

    細菌只是生活在你的腸道。而他們將是寡不敵眾 大約10到一個由

  • viruses living in your gut. So we're going to have quadrillion viruses living in your

    病毒生活在你的腸道。所以,我們將有四萬億病毒 生活在你的腸道。

  • gut. Now viruses aren't technically cells, but everything else I've described here is

    腸道。現在,病毒不是技術上的細胞,但其他一切我'這裡描述的是。

  • going to be reproducing or it's going to be created through a process called cell division.

    將會進行繁殖,或者它將會通過一個叫做細胞分裂的過程被創造出來。

  • And there are really three types of cell division. In prokaryotic cells, or in bacteria, they're

    而細胞分裂其實有三種類型。在原核細胞或細菌中,它們是:

  • simply going to divide through a process called binary fission. That's where one cell, one

    只是要通過一個叫做二元裂變的過程來分裂。這就是一個細胞,一個

  • bacteria cell, is going to make two cells that are exact copies of the original cell.

    細菌細胞,是要製造出兩個完全複製原細胞的細胞。

  • In eukaryotic cells we have something similar to this. We're going to have cell division

    在真核細胞中,我們有類似的東西。我們要進行細胞分裂。

  • or we sometimes just refer to it as mitosis. Technically mitosis is going to be division

    或者我們有時就把它稱為有絲分裂。從技術上講,有絲分裂就是要分裂

  • of the nuclei. And then we're going to have cytokinesis which is division of the rest

    細胞核的。然後我們會有細胞分裂,這是其餘的分裂。

  • of the cell. But we generally just say mitosis is when one eukaryotic cell makes two cells

    的細胞。但我們一般只是說有絲分裂是一個真核細胞製造兩個細胞的時候

  • that are exact copies of that cell. It's a lot like binary fission. And then the third

    是該細胞的精確拷貝。這很像二元裂變。然後第三種

  • type of cell division is going to be meiosis. Meiosis is going to be when we create sex

    細胞分裂的類型將是減數分裂。減數分裂將是我們創造性的時候。

  • cells. Or when we create gametes. Mitosis and binary fission insure that we have exact

    細胞。或者當我們創造配子時。有絲分裂和二元裂變保證了我們有確切的。

  • duplicates of that original cell. Meiosis is totally different. Meiosis is going to

    該原始細胞的副本。減數分裂則完全不同。減數分裂是要

  • make cells that are different. They're going to have half the genetic information and they're

    使細胞是不同的。他們將有一半的遺傳信息和他們的。

  • going to give us variability. And so in us sex is important because it gives us variability

    會給我們帶來變異性。所以對我們來說,性是很重要的,因為它給我們帶來了變異性

  • in the next generation. In bacteria mutation and there's some other ways that they can

    在下一代。在細菌突變和有一些其他的方式,他們可以。

  • share information is more important. So let's start by talking about bacteria. They reproduce

    分享資訊更重要。所以,讓我們'從細菌開始說起。它們的繁殖

  • through a process called binary fission. In this we're going to have this adult cell,

    通過一個叫做二元裂變的過程。在這個我們'要有這個成體細胞。

  • so we're going to have this parent cell. It's going to be made up of, you can see here,

    所以我們將有這個父細胞。它將會由,你可以看到這裡。

  • ribosomes. It's going to have a plasmid here which is a little bit of extra DNA. But it's

    核糖體。它將有一個質粒在這裡 這是一個有點額外的DNA。但它

  • genome or all of its DNA is going to be wrapped up into one loop. And so what do we want to

    基因組或其所有的DNA將被包裹成一個循環。所以我們要做的是

  • do in binary fission? We want to take one cell and we want to make two cells that are

    做二元裂變?我們想用一個細胞來製造兩個細胞,這兩個細胞是...

  • identical to that. And so the process is pretty simple. What the bacteria cell starts doing

    與此相同。所以這個過程非常簡單。細菌細胞開始做什麼

  • is duplicating all of its DNA. So the first thing it will do is DNA polymerase goes around

    正在複製所有的DNA。所以它要做的第一件事就是DNA聚合酶繞著它跑

  • the whole loop and it's going to make an exact copy of all the DNA in the bacteria. One thing

    整個循環,它'的要做一個精確的副本 所有的DNA在細菌。有一件事

  • not shown in here is that we're also going to duplicate our plasmids. And we're also

    在這裡沒有顯示的是,我們'也要複製我們的質粒。而且我們'也

  • going to have, you know, ribosomes increasing as we increase the number of DNA as well.

    將有,你知道,核糖體增加 當我們增加DNA的數量,以及。

  • What happens next is it's going to be pulled to the side of that cell. And really what's

    接下來發生的事情就是它'會被拉到那個小區的旁邊。而真正的...

  • going to happen is the DNA will actually attach to the cell wall. And then eventually that

    將會發生的是DNA將實際附著在細胞壁上。然後最終

  • cell wall is going to split in half and we're going to have two bacteria cells. How are

    細胞壁將分裂成兩半,我們'將有兩個細菌細胞。如何是

  • they different? They're not really different. They're exactly the same. The DNA in this

    他們不同?他們並沒有真正的不同。他們是完全一樣的。這裡面的DNA

  • cell and the DNA in this cell is going to be exactly the same. And when we divide in

    細胞和這個細胞中的DNA是完全一樣的。而當我們分裂的時候

  • half, we're going to divide in half those ribosomes and the plasmids as well. And so

    一半,我們'要抽成一半那些核糖體和質粒也是如此。我們要把這些核糖體和質粒也抽成兩半

  • again, bacteria don't do mitosis. They don't have sex. They simply reproduce through binary

    再次,細菌不'不做有絲分裂。他們不'沒有性別。它們只是通過二元繁殖

  • fission. And this happens incredibly quickly. So in a typical e. coli they can copy themselves,

    裂變。而且這種情況發生得非常快所以在一個典型的大腸桿菌中,它們可以複製自己。

  • make two copies of one cell, in 20 minutes. Which is just crazy how fast that occurs.

    在20分鐘內將一個細胞複製兩份。這就是瘋狂的發生速度。

  • But again we don't go through binary fission because we're eukaryotic cells. And before

    但我們又不經過二元裂變,因為我們'是真核細胞。而之前

  • we talk about mitosis and meiosis, we should make sure you know the difference between

    我們談論有絲分裂和減數分裂,我們應該確保你知道兩者之間的區別。

  • what a gamete is and then a somatic cell. And so eukaryotic cells are going to be everything

    什麼是配子,然後是體細胞。所以真核細胞將成為所有的東西

  • from the chimpanzee to the bees to the flowers to the mushroom to the yeast, they all have

    從黑猩猩到蜜蜂到花兒到蘑菇到酵母,它們都有...

  • a nuclei. And so there are two types of cells that we find inside eukaryotic organisms.

    一個細胞核。所以我們在真核生物體內發現了兩種類型的細胞。

  • First are going to be the somatic cells. Somatic cells are going to be the body cells in your

    首先是會是體細胞。體細胞將是你的身體細胞。

  • body. And then we're going to have the gametes which are going to be the sex cells. So in

    身體。然後我們'將有配子 這將是性細胞。所以在

  • humans the only cells inside our body that are going to be gametes are going to be sperm

    人類體內唯一能成為配子的細胞就是精子。

  • in males and then the eggs or the ovum that are found inside females. How are they different?

    在雄性體內的卵子或卵子,然後在雌性體內發現。它們有什麼不同?

  • Remember somatic cells are the body cells that are going to be diploid in humans. They're

    記住體細胞是人類要二倍體的體細胞。他們'是

  • going to have two copies of every gene. And therefore two copies of every chromosome.

    將有兩個副本 每個基因。是以每條染色體都有兩個拷貝。

  • Gametes are only going to have one. So sperm and egg each provide you with half the DNA

    配子是隻會有一個的。所以精子和卵子各為你提供一半的DNA。

  • that you get. So how do we duplicate a typical cell? Well first we should say when do we

    你得到的。那麼我們如何複製一個典型的細胞呢?好吧,首先我們應該說,當我們

  • do that? Well remember when you go from a zygote to an adult, we're doubling the cells

    做到這一點? - 好吧,記得當你從胚胎到成人,記得當你從一個胚胎變成一個成年人的時候 我們的細胞就會翻倍

  • over and over and over again. And then we're constantly replacing the cells in our body.

    一遍又一遍。然後我們'不斷地更換體內的細胞。

  • So as cells become worn out or damaged or removed we have to replace those with other

    所以,當細胞磨損、損壞或被移除時,我們必須用其他的細胞來替代這些細胞。

  • cells. And we do that through mitosis. Again what is mitosis? It's technically the division

    細胞。我們通過有絲分裂來實現。同樣什麼是有絲分裂?它的技術上的分裂

  • of the nuclei, but then we're going to have division of the rest of the cell which is

    細胞核,但隨後我們'將有分裂 細胞的其餘部分,這是。

  • called cytokinesis. So what do we start with? And we're going to make this real simple,

    稱為細胞運動學。那麼我們從什麼開始呢?而我們'將使這個真正的簡單。

  • this is a simple cell. It's a diploid cell. It's 2n=2. That means they have two chromosomes.

    這是一個簡單的細胞。這是一個簡單的細胞。 這是一個二倍體細胞。它是2n=2。這意味著他們有兩條染色體。

  • These two chromosomes are going to be homologous. That means that they're the same length. The

    這兩條染色體將是同源的。這意味著他們'是相同的長度。這

  • reason why they're different colors is you get on from one parent and one from another.

    為什麼他們'不同的顏色的原因是你從一個父母和一個從另一個得到上。

  • And so in mitosis, let's look first before we talk about the specifics of what we're

    所以在有絲分裂中,我們先來看看,然後再來談談我們的具體內容。

  • going to get out of mitosis. We're going to start with one cell looks like this. And we're

    要走出有絲分裂。我們要開始與一個細胞看起來像這樣。我們要從一個像這樣的細胞開始

  • going to end up with two cells that look exactly like that first cell. So in mitosis we want

    最終會有兩個和第一個細胞一模一樣的細胞。所以在有絲分裂過程中,我們要

  • to duplicate the cell. And so let's watch that. What's the first thing that happens

    來複制細胞。所以,讓我們'觀看。首先發生的事情是什麼?

  • is we have to duplicate all of the DNA. And this occurs during interphase. What's going

    是我們必須複製所有的DNA。而這發生在間期。什麼?

  • to happen is this chromosome right here is going to copy all of its DNA. And now we're

    這條染色體將複製所有的DNA。現在我們

  • going to have what are called sister chromatids. And so we have a chromosome on this side.

    會有所謂的姐妹染色體。所以,我們有一個染色體 在這一側。

  • A chromosome on this side. And they're exactly the same. So they're an exact duplicate of

    這邊的一條染色體。而且它們是完全一樣的。所以他們是一個完全重複的。

  • that original chromosome. And you can see that we're going to have that on the other

    原始染色體。你可以看到,我們'將有 在另一個。

  • homologous chromosome as well. What happens next? They're going to meet in the middle.

    同源染色體也是如此。接下來會發生什麼?他們'會在中間相遇。

  • They're going to line up. These lines represent a spindle which is going to attach to either

    他們'要排成一條線。這些線條代表了一個主軸,它將連接到任何一個地方。

  • side. Each of those sister chromatids and then they're going to be pulled apart. They're

    一邊。每一個姐妹染色體,然後他們'將被拉開。姐妹染色體

  • going to be pulled apart. And eventually, so this would be the mitosis when we divide

    會被拉開。最終,所以這將是有絲分裂,當我們分裂的時候,

  • the nuclei. And then the whole cell is going to split in half. We're going to divide that

    細胞核。然後整個細胞將被一分為二。我們要把它抽成兩半

  • cytoplasm and that's called cytokinesis. And so what do we end up with? We end up with

    細胞質和'叫細胞分裂。所以,我們最終與什麼?我們的結局是

  • two cells that are both diploid. Our original cell was diploid as well. So let's take a

    兩個細胞,都是二倍體。我們原來的細胞也是二倍體。所以,讓我們以

  • look at what this really looks like. We're looking right here at cells that are undergoing

    看看這到底是什麼樣子。我們現在看到的是正在進行中的細胞。

  • mitosis. And so they're growing on a growth medium. And if we just play the video, this

    有絲分裂。所以他們'生長在一個生長介質上。如果我們只是播放視頻,這

  • is time lapsed. And so it's speeding it up quite a bit. But what will happen if we look

    是時間的推移。所以它'的速度相當快。但是,如果我們看看會發生什麼

  • at like this cell right down here, is that you can see it kind of come together in the

    在像這樣的細胞就在這裡, 是,你可以看到它的那種走到一起的。

  • nuclei's dividing up the genetic information. And then the rest of the cell is going to

    細胞核正在分割遺傳信息。細胞的其餘部分將是

  • divide. What do we end up with when we're done with that? We have two identical cells.

    分裂。當我們做完這一切後,我們最終會得到什麼?我們有兩個相同的細胞。

  • And those are going to grow. And then they're eventually going to divide the nuclei and

    而這些都會成長。然後他們最終會分裂出細胞核和

  • they're going to grow. And they're going to grow. And they're going to grow. And cells,

    他們'要成長。而他們'要成長。他們會成長。 而他們'要成長。和細胞。

  • unless they're cancer cells, are going to keep growing on here until they fill up this

    除非他們'是癌細胞,要保持增長在這裡,直到他們填補了這個

  • whole medium. But we need to talk about meiosis, which is the third type of cell division.

    整個介質。但我們需要談談減數分裂,這是細胞分裂的第三種類型。

  • What happens in meiosis. Meiosis is when you take one cell and we're going to make four

    減數分裂中發生了什麼。減數分裂是當你把一個細胞和我們'要做四個。

  • cells out of it. Now let's look how this is a little different than in mitosis. In mitosis

    細胞出來的。現在讓我們來看看這與有絲分裂中的情況有什麼不同。在有絲分裂中

  • remember we took one cell and we made two cells. In meiosis we're actually going to

    記得我們把一個細胞和我們做了兩個細胞。在減數分裂中,我們實際上要

  • have another division. But there's something even different that we didn't see in mitosis.

    有另一個分部。但有'的東西甚至不同,我們在有絲分裂中沒有看到。

  • Remember in mitosis we want to make sure that each of the cells that we make are identical

    記住,在有絲分裂中,我們要確保我們製造的每一個細胞都是相同的。

  • to that original cell. You can see here that the four cells that we create at the end are

    到那個原始單元格。在這裡你可以看到,我們在最後創建的四個單元格是

  • going to be totally different than that original cell. And they're going to have half the genetic

    將是完全不同的 比原來的細胞。他們將有一半的基因。

  • information. Remember I said the sperm and the egg have half the information that's found

    資訊。記得我說過精子和卵子有一半的資訊,'的發現。

  • in the original cell. And so what's going happen? Well let's watch how this begins.

    在原來的細胞中。那麼會發生什麼呢?好吧,讓我們來看看這是如何開始的。

  • The first thing that happens is you're going to duplicate each of these chromosomes. And

    第一件事就是你'要複製這些染色體的每一條。而

  • so we're going to make copies of the chromosomes. But then something odd happens. What happens

    所以我們'要對染色體進行復制。但後來發生了一些奇怪的事情。發生了什麼?

  • that's odd, we're going to take a little bit, in the case we're going to take a little bit

    這是奇怪的,我們將採取一點點,在這種情況下,我們將採取一點點。

  • of this white chromosome here. And it's going to cross over with this red chromosome right.

    這個白色染色體的這裡。和它'的要交叉 與這個紅色的染色體權利。

  • So we're actually swapping chromosomes. And so that process is called crossing over but

    所以我們實際上是在交換染色體。所以這個過程被稱為越界,但

  • what you're really doing is your crossing over or your making a new chromosome. It's

    你真正做的是你的交叉或你做一個新的染色體。它是

  • a combination of the chromosome you got from your mom and your dad. It's a chromosome that's

    你從你的媽媽和你的爸爸得到的染色體的組合。它是一個染色體,它的

  • never been built before. So those will eventually line up in the middle. And then they're going

    從來沒有建過。所以,這些最終會排在中間。然後他們'要

  • to divide. And then they're going to divide again. And so they'll divide in half. So this

    分裂。然後他們'要再次分裂。所以他們'會一分為二。所以這

  • is meiosis one and then they'll divide in half again. And that is called meiosis two.

    是減數分裂一,然後他們'會再次分裂成兩半。這就是所謂的減數第二次分裂。

  • So what do we create when we're done. We're going to create daughter cells. But each of

    那麼,當我們'完成後,我們要創建什麼。我們'要創造子細胞。但每個

  • those daughter cells are going to be different. Each of these would create a new sperm or

    這些子細胞將是不同的。每一個子細胞都會創造出一個新的精子,或者說是一個新的子細胞。

  • a new egg. Now it's going to be much more complicated in us, in humans, remember, we're

    一個新的雞蛋。現在,這將是更復雜的我們,在人類,記住,我們'。

  • not going to start with 2n=4. With 4 total chromosomes here. We're going to start with

    不打算從2n=4開始。與4總染色體在這裡。我們要從

  • 2n=46. And so we're going to start with 46 chromosomes. So it's going to be really really

    2n=46.所以我們要從46條染色體開始。所以,這將是真的真的真的

  • different when we get to the end. And so we can create literally billions and billions

    不同的時候,我們得到的最後。所以我們可以創造出數以億計的東西

  • of different types of cells through meiosis. And so that's going to give us variation.

    的不同類型的細胞通過減數分裂。所以,這'將給我們的變化。

  • So to summarize. What do we have? We have three types of cell division. We've got binary

    所以要總結一下。我們有什麼?我們有三種類型的細胞分裂。我們有二元分裂

  • fission. That's going to be found just in bacteria where you take one bacteria, first

    裂變。這'要在細菌中就能發現,你把一個細菌,先是。

  • copy the DNA and then the rest of the cell is going to divide through cytokinesis. Each

    複製DNA,然後細胞的其他部分通過細胞分裂。每個

  • of these daughter cells is going to be identical to that first cell. If you're looking at eukaryotic

    這些子細胞的要和第一個細胞相同。如果你看的是真核細胞

  • cells, we've got mitosis. What happens in mitosis? We start with a diploid cell. So

    細胞,我們已經得到了有絲分裂。有絲分裂會發生什麼?我們開始與二倍體細胞。所以...

  • here are the reds and the greens are each going to come from different parents. So we

    這裡的紅色和綠色都是來自不同的父母。所以我們

  • have four chromosomes. They're going to duplicate first during S phase of interphase. They'll

    有四條染色體。它們會在間期的S階段首先複製。他們將

  • line up in the middle. And they'll be pulled to the side. Now if we look here, these two

    排在中間。而他們'會被拉到一邊。現在如果我們看這裡,這兩個

  • cells that are produced in mitosis are identical to that original cell. And that's what mitosis

    在有絲分裂中產生的細胞與該原始細胞是相同的。而這正是有絲分裂

  • does. It makes exact copies. If we start with meiosis, meiosis is going to start with an

    是的它能做出精確的拷貝。如果我們從減數分裂開始,減數分裂將從一個新的開始。

  • original cell that looks very similar. But instead of lining up like this where we separate

    原始單元格,看起來非常相似。但我們不是像這樣排成一排,在這裡,我們分開了

  • the sister chromatids, they're going to line up with the homologous chromosomes wrapping

    姐妹染色體,它們將與包裹著同源染色體的同源染色體排在一起

  • around each other and swapping bits of that chromosome. They'll divide in half. And then

    互相圍繞,交換該染色體的位。它們會一分為二。然後

  • they're going to divide in half again. And what we're going to create is gametes. Those

    他們將再次分裂成兩半。而我們要創造的是配子。那些...

  • are going to be sperm and egg that have half the genetic information in a new combination

    將是精子和卵子,有一半的遺傳信息的新組合。

  • of that genetic information. So again, this will be fertilized by a different sperm and

    的遺傳信息。所以,這將再次受精 由不同的精子和。

  • we get back to a zygote. Where do we go from the zygote? We go right back here to mitosis

    我們又回到了胚胎。我們從胚胎到哪裡去?我們回到這裡的有絲分裂

  • where we can copy that cell over and over and over and over again. And so that's cell

    在那裡,我們可以複製該單元格一遍又一遍,一遍又一遍。所以這就是單元格

  • division. It's found in all cells on our planet. It shows how one cell can go to all the cells

    分裂。它'在我們地球上的所有細胞中都能找到。它顯示了一個細胞如何去所有的細胞。