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  • Every cell in your body

    你體內的每一個細胞

  • is separated from those around it

    用最外面的一層

  • by its outermost layer,

    和外界分隔,

  • its membrane.

    這層叫做細胞膜。

  • A cell membrane must be both sturdy and flexible.

    細胞膜必須要又穩固又有彈性。

  • Imagine a membrane made of metal -

    想像金屬製的細胞膜

  • great at keeping the cell's guts inside,

    ──可以把細胞內部保存得很好,

  • but horrible at letting materials flow in and out.

    可是很難讓物質進進出出。

  • But a membrane made of fishnet stocking

    但漁網做的細胞膜

  • would go too far in the opposite direction -

    會恰恰相反

  • leaky, but easily torn.

    ──方便進去,但是容易破。

  • So, the ideal membrane falls somewhere in the middle.

    所以,理想的細胞膜 應該介於中間。

  • Over the past few centuries,

    經過幾個世紀以後,

  • we've learned a lot about the way membranes work.

    我們在細胞膜的運作方式這方面 學到了很多。

  • The tale starts in the late 1800's

    這個故事要從 1800 末期講起,

  • when, according to legend,

    據說,

  • a German woman named Agnes Pockels was doing dishes.

    一位叫做 Agnes Pockels 的德國女性 在做菜時發現的。

  • Her observation, that not all detergents

    她觀察到,不是所有的清潔劑

  • dissolve grease in the same way,

    都用同樣的方式 溶解油汙,

  • piqued her curiosity,

    這激起了她的好奇心,

  • so she made careful measurements

    所以她仔細地測量

  • of the size of soapy films

    裝水的金屬盤

  • that formed on the surface

    表面所形成的

  • of a metal tray filled with water.

    肥皂膜的厚度。

  • Later, in the 1920's, GE scientists

    後來,在 1920 年代, 電子學家

  • Irving Langmuir and Katharine Blodgett

    Irving Langmuir 和 Katharine Blodgett

  • reexamined the problem with a more elaborate contraption

    用更精細的發明 再次檢驗這個問題,

  • and found that those tiny slicks

    然後發現這薄薄的一層

  • were in fact a single layer of oil molecules.

    實際上就是 單一一層的油分子。

  • Each oil molecule has one side

    每個油分子有一側

  • that loves water and floats on the surface,

    是喜歡水的,所以飄浮在水的表面;

  • and one side that loathes water

    另一側則討厭水,

  • and protrudes into the air.

    因此朝向空氣。

  • So what does it have to do with cell membranes?

    所以這個細胞膜有什麼關係?

  • Well, at the turn of the 20th century,

    嗯,在 20 世紀交替的時候,

  • chemists Charles Overton and Hans Meyer

    化學家 Charles Overton 和 Hans Meyer

  • demonstrated that the cell membrane

    證實了細胞膜

  • is composed of substances that,

    是由類似油的物質形成,

  • like oil,

    是由類似油的物質形成,

  • have a water-loving part

    有一側親水端

  • and a water-loathing part.

    還有一側厭水端。 (譯註:或稱疏水端。)

  • We now call these substances lipids.

    我們現在把這個物質 叫做脂質。

  • In 1925, two scientists,

    在 1925 年,兩位科學家

  • Evert Gorter and Francois Grendel,

    Evert Gorter 和 Francois Grendel

  • pushed our understanding further.

    把我們的認知更往前推。

  • They designed an experiment meant to test

    他們設計了一個實驗,

  • whether cell membranes

    來測試細胞膜

  • are made of only one layer of lipids,

    是由一層脂質組成,

  • a monolayer,

    也就是單層膜,

  • or two layers stacked on top of one another,

    或是兩層疊在一起 所組成,

  • called a bilayer.

    也就是雙層膜。

  • Gorter and Grendel drew blood

    Gorter 和 Grendel 從

  • from a dog,

    狗、

  • a sheep,

    綿羊、

  • a rabbit,

    兔子、

  • a goat,

    山羊、

  • a guinea pig,

    天竺鼠、

  • and human volunteers.

    還有人類自願者 身上抽血。

  • From each of these samples,

    從這些樣本中,

  • they extracted all the lipids

    他們把所有脂質

  • from all the red blood cells

    都從紅血球中 萃取出來

  • and placed a few drops of this extract

    然後滴一滴 萃取液

  • on a tray of water.

    在水盤之上。

  • True to form, the lipids, like oil,

    正如預期,就像油一樣,

  • spread out into a monolayer,

    脂質散開形成單層膜,

  • whose size Gorter and Grendel could measure.

    而 Gorter 和 Grendel 可以測量它的大小。

  • If they compared the surface area of that monolayer

    如果他們把這單層膜的表面積

  • to the surface area to the intact red blood cells,

    和完整的紅血球表面積相比,

  • they'd be able to tell

    他們就有辦法判定

  • whether the red blood cell membrane

    紅血球的細胞膜

  • is one or two layers thick.

    是一層還兩層。

  • To understand the design of their experiment,

    要了解這個實驗的設計,

  • imagine looking down at a sandwich.

    想想由上往下看著三明治。

  • If you measure the surface area of what you see,

    如果你估測你看到的面積,

  • you'll get the dimensions of a single slice of bread

    你會覺得它是一層而已,

  • even though there are two slices,

    儘管它有兩層,

  • one stacked perfectly atop the other.

    第一層完全把第二層蓋住了。

  • But, if you open the sandwich

    但是,如果你把三明治打開

  • and place the two slices side by side,

    然後把兩片放在一起,

  • you get twice the surface area.

    你就會得到兩倍的表面積。

  • The Gorter and Grendel experiment

    而 Gorter 和 Grendel 的實驗

  • is basically the same idea.

    基本上就是這個想法。

  • The open sandwich is the monolayer formed

    打開的三明治相當於單層膜,

  • by extracted cellular lipids spreading out into a sheet.

    它是由萃取的細胞脂質 擴散成一個平面。

  • The closed sandwich is the intact red blood cell membrane.

    而蓋好的三明治就相當於 完整的紅色球細胞膜。

  • Low and behold, they observed a two-to-one ratio,

    驚奇的是,他們發現了 2 比 1 的比例,

  • proving beyond the shadow of a doubt

    確實證明

  • that a cell membrane is a bilayer,

    細胞膜是雙層膜,

  • which when unstacked,

    因為當它們沒疊在一起時,

  • yields a monolayer twice its size.

    產生的單層膜有兩倍的面積。

  • So almost 30 years before the double-helix structure

    所以幾乎是 DNA 雙螺旋結構

  • of DNA was elucidated,

    被發現的 30 年前,

  • a single experiment

    就靠一個實驗,

  • involving fancy versions of household materials

    它包含了對家務事的新潮想法,

  • enabled deep insight

    讓對於細胞基本結構

  • into the basic architecture of the cell.

    的更深層認識變為可能。

Every cell in your body

你體內的每一個細胞

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B2 中高級 中文 TED-Ed 細胞膜 脂質 表面積 三明治 紅血球

TED-Ed】通過餐具洗滌劑瞭解細胞膜--Ethan Perlstein。 (【TED-Ed】Insights into cell membranes via dish detergent - Ethan Perlstein)

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    wikiHuang 發佈於 2021 年 01 月 14 日
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