Name: 細胞膜比你想象的要複雜得多--Nazzy Pakpour。 (Cell membranes are way more complicated than you think - Nazzy Pakpour)
Uploaded: 2021-01-14T08:36:02.000Z
Duration: 5 min 21 s

Cell membranes are structures of contradictions.

These oily films are hundreds of times thinner than a strand of spider silk,

這些油膜比一縷蜘蛛絲薄上數百倍

yet strong enough to protect the delicate contents of life:

然而強韌至足以保護  生命精緻的內含物質：

the cell's watery cytoplasm, genetic material, organelles,

質地似水的細胞質、 遺傳物質、細胞器

and all the molecules it needs to survive.

How does the membrane work, and where does that strength come from?

細胞膜是如何運作以及從哪裡獲得力量？

First of all, it's tempting to think of a cell membrane

but it's actually something  much more complex.

shifting components back and forth to help the cell take in food,

來回移動各種組成 以幫助細胞攝食

gather information about the environment,

The cell membrane gets this resilience, flexibility, and functionality

細胞膜具有回彈性、柔靭性及功能性

by combining a variety  of floating components

這就是生物學家 所謂的「流動鑲嵌模型」

The primary component of the fluid mosaic

is a simple molecule  called a phospholipid.

是一種簡單的分子稱為「磷脂」

A phospholipid has a polar,  electrically-charged head,

They pair up tail-to-tail in a two layer sheet

它們尾端對尾端配對 形成兩層的薄面

just five to ten nanometers thick that extends all around the cell.

只有 5-10 nm 的厚度 環繞整個細胞

and out towards the watery fluid  external to the cell

with the lipid tails  sandwiched in between.

This bilayer, which at body temperature has the consistency of vegetable oil,

這脂質雙層在體溫下 具有植物油的黏稠度

is studded with other types of molecules,

Cholesterol keeps the membrane  at the right fluidity.

It also helps regulate communication between cells.

by releasing and capturing  chemicals and proteins.

是藉著化學物質 與蛋白質的釋放與捕捉

but the capture of them  is more complicated.

That happens through a process called endocytosis

in which sections of the membrane engulf substances

and transport them into the cell as vesicles.

然後形成小囊泡 將它們送入細胞內

the vesicles are recycled and returned to the cell membrane.

小囊泡則被回收 重新回到細胞膜

The most complex components of the fluid mosaic are proteins.

流動鑲嵌模型最複雜的成分是蛋白質

that the right molecules  get in and out of the cell.

can cross the phospholipid  bilayer easily.

But polar and charged molecules can't make it through the fatty inner layer.

但極性、帶電分子 則無法通過脂質內層

Transmembrane proteins stretch across the bilayer to create channels

「跨膜蛋白」跨過 整個脂質雙層而形成通道

that allow specific molecules through, like sodium and potassium ions.

能讓特定的分子通過 如鈉和鉀離子

Peripheral proteins floating in the inner face of the bilayer

浮在脂質雙層內側的「膜周邊蛋白」

help anchor the membrane to the cell's interior scaffolding.

會協助細胞膜 固定於細胞的內支架

Other proteins in cell membranes can help fuse two different bilayers.

細胞膜上的其他蛋白質 能協助融合兩個不同的雙層

That can work to our benefit, like when a sperm fertilizes an egg,

這能有利於我們 如精子使卵子受精

but also harm us, as it does when a virus enters a cell.

但也能傷害我們 例如病毒侵入細胞時

And some proteins move within the fluid mosaic,

有些蛋白質 在流動鑲嵌模型的裡面流動

coming together to form complexes that carry out specific jobs.

聚集形成執行特殊任務的複合物

For instance, one complex might activate cells in our immune system,

例如一種複合物 能激活免疫系統的細胞

Cell membranes are also the site of an ongoing war

between us and all the things that want to infect us.

In fact, some of the most toxic substances we know of

事實上，我們知道一些最毒的物質

are membrane-breaching proteins made by infectious bacteria.

是由感染細菌製造的破膜蛋白質

These pore-forming toxins poke giant holes in our cell membranes,

這些「形成微孔毒素」 在細胞膜上戳出大洞

Scientists are working on developing ways to defend against them,

科學家們正在研發對抗它們的方法

like using a nano-sponge that saves our cells

如使用一種奈米海綿來解救細胞

by soaking up the membrane-damaging toxins.

The fluid mosaic is what makes  all the functions of life possible.

流動鑲嵌模型使得所有生命的功能變得可能

Without a cell membrane, there could be no cells,

and without cells, there would be no bacteria,

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細胞膜比你想象的要複雜得多--Nazzy Pakpour。 (Cell membranes are way more complicated than you think - Nazzy Pakpour)

constantly

specific

immune

material