Plasma Membrane · 质膜
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| plasma membrane/ˈplæzmə ˈmembreɪn/ | 质膜 | zhì mó |
| phospholipid bilayer/ˈfɒsfəlɪpɪd ˈbɪleɪə/ | 磷脂双分子层 | lín zhī shuāng fèn zǐ céng |
| fluid mosaic/ˈfluːɪd məˈseɪɪk/ | 流动镶嵌 | liú dòng xiāng qiàn |
| selectively permeable/sɪˈlektɪvli ˈpɜːməbl/ | 选择性通透的 | xuǎn zé xìng tōng tòu de |
The cell's border
- Every cell is wrapped in a thin skin: the plasma membrane.
- It decides what gets in, what stays out, and what leaves.
- It is only two molecules thick, yet it controls the whole cell's traffic.
- Its clever design comes straight from the phospholipids you met earlier.
细胞的边界
- 每个细胞都裹着一层薄薄的皮:质膜。
- 它决定什么进来、什么留在外面、什么离开。
- 它只有两个分子那么厚,却控制着整个细胞的运输。
- 它巧妙的设计正来自你先前认识的磷脂。
A phospholipid bilayer
- The plasma membrane 质膜 is built from a phospholipid bilayer 磷脂双分子层.
- Water-loving heads face the watery outside and inside.
- Water-fearing tails hide in the middle, away from water.
- This double layer forms a stable, self-sealing sheet around the cell.
磷脂双层
- 质膜(plasma membrane)由一个磷脂双层(phospholipid bilayer)构成。
- 亲水的头朝向外面和里面的水。
- 疏水的尾藏在中间,远离水。
- 这个双层在细胞周围形成一张稳定、能自我封闭的片。
The plasma membrane is built mainly from a… · 质膜主要由……构成。
The membrane is a phospholipid bilayer — two layers of phospholipids with proteins embedded in them. · 膜是一个磷脂双层——两层磷脂,里面嵌着蛋白质。
A fluid mosaic
- The membrane is not rigid — the lipids drift like a fluid.
- Proteins are scattered through it like tiles in a fluid mosaic 流动镶嵌.
- Some proteins are channels; some are pumps; some are receptors.
- Cholesterol sits between the lipids to keep the membrane steady.
流动镶嵌
- 膜不是刚硬的——脂质像流体一样漂移。
- 蛋白质像瓷砖一样散布在其中,构成一个流动镶嵌(fluid mosaic)。
- 有些蛋白质是通道;有些是泵;有些是受体。
- 胆固醇坐在脂质之间,让膜保持稳定。
The model of the membrane, with proteins floating in a moving lipid sheet, is the ____ mosaic model. · 膜的模型——蛋白质漂浮在流动的脂质片中——叫做____镶嵌模型。
In the fluid mosaic model the lipids move like a fluid, and proteins are scattered through them like a mosaic. · 在流动镶嵌模型里,脂质像流体一样移动,蛋白质像马赛克一样散布在其中。
Selectively permeable
- The membrane is selectively permeable 选择性通透的: it lets some things cross, not others.
- Small nonpolar molecules (like oxygen) slip straight through the oily middle.
- Charged ions and large molecules cannot — they need protein help.
- This control is how the cell keeps its inside different from its surroundings.
选择透过性
- 膜是选择透过性(selectively permeable)的:它让一些东西穿过,另一些不行。
- 小的非极性分子(比如氧气)直接滑过油性的中间。
- 带电的离子和大分子不行——它们需要蛋白质帮忙。
- 这种控制,就是细胞让内部与周围保持不同的方式。
Parts of the membrane · 膜的组成部分
Sort each membrane part by the job it does in the fluid mosaic. · 按照每个膜的部件在流动镶嵌中做的工作,给它们分类。
The membrane is selectively permeable — it lets some substances cross but not others. · 膜是选择透过性的——它让一些物质穿过,而另一些不行。
Being selectively permeable lets the cell control exactly what enters and leaves. · 选择透过性让细胞精确地控制什么进出。
Which crosses the lipid bilayer most easily on its own? · 哪一种最容易自己穿过脂质双层?
Small nonpolar molecules slip through the oily core; charged or large molecules need a protein to help. · 小的非极性分子能滑过油性的核心;带电或大的分子需要蛋白质帮忙。
Select all · 所有 true statements about the plasma membrane. · 选出关于质膜的所有正确说法。
The membrane is fluid and flexible, not a solid wall. The other three are correct. · 膜是流动而柔软的,不是坚硬的墙。其余三条正确。
The membrane is not a solid wall. It is a flexible, moving sheet only two molecules thick. Picture a layer of oil droplets on water, not a brick wall — it can bend, flow, and even reseal itself.
膜不是一堵坚硬的墙。它是一张柔软、流动、只有两个分子厚的片。想象水面上的一层油滴,而不是砖墙——它能弯曲、流动,甚至能自我重新封闭。
Why oxygen crosses but sodium needs help:
- Oxygen is small and nonpolar, so it dissolves through the lipid tails freely.
- A sodium ion carries a charge, so the oily core repels it.
- Sodium must pass through a protein channel or pump — it cannot cross on its own.
氧气为什么能穿过,而钠需要帮忙:
- 氧气小而非极性,所以它自由地溶解穿过脂质尾。
- 一个钠离子带电荷,所以油性的核心排斥它。
- 钠必须通过蛋白质通道或泵——它不能自己穿过。
The plasma membrane is a phospholipid bilayer with proteins scattered through it — the fluid mosaic model. It is selectively permeable: small nonpolar molecules cross freely, while charged or large molecules need protein channels or pumps. This is how the cell controls its traffic.
质膜是一个磷脂双层,蛋白质散布在其中——这就是流动镶嵌模型。它是选择透过性的:小的非极性分子自由穿过,而带电或大的分子需要蛋白质通道或泵。这就是细胞控制运输的方式。