Facilitated Diffusion · 易化扩散
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| facilitated diffusion/fəˈsɪlɪteɪtɪd dɪˈfjuːʒn/ | 易化扩散 | yì huà kuò sàn |
| channel protein/ˈtʃænl ˈprəʊtiːn/ | 通道蛋白 | tōng dào dàn bái |
| carrier protein/ˈkærɪə ˈprəʊtiːn/ | 载体蛋白 | zài tǐ dàn bái |
A door for the stuck molecules
- Oxygen slips through the membrane freely, but many molecules cannot.
- A charged ion or a large sugar is blocked by the oily middle.
- Yet cells still need these substances to cross.
- The answer is a doorway built from protein.
给被卡住的分子一扇门
- 氧气自由地滑过膜,但许多分子做不到。
- 一个带电的离子或一个大的糖被油性的中间挡住。
- 然而细胞仍然需要这些物质穿过。
- 答案是一扇由蛋白质构成的门。
Why some molecules are blocked
- The membrane's core is made of water-fearing fatty tails.
- Charged particles and large polar molecules are repelled by this oily layer.
- On their own, they simply cannot get through.
- They need a helper embedded in the membrane.
有些分子为什么被挡住
- 膜的核心由怕水的脂肪尾构成。
- 带电的粒子和大的极性分子被这层油性的层排斥。
- 靠它们自己,根本过不去。
- 它们需要一个嵌在膜里的帮手。
Why do some molecules need facilitated diffusion instead of crossing the bilayer directly? · 为什么有些分子需要易化扩散,而不能直接穿过双层?
Charged ions and large polar molecules cannot cross the oily core, so a protein must help them. · 带电的离子和大的极性分子无法穿过油性核心,所以蛋白质必须帮它们。
Channels and carriers
- Facilitated diffusion 易化扩散 is diffusion helped by a membrane protein.
- A channel protein 通道蛋白 is a lined pore that lets specific particles pass.
- A carrier protein 载体蛋白 binds a molecule, then changes shape to release it on the other side.
- Each protein is specific — shaped to fit just one kind of particle.
通道与载体
- 易化扩散(facilitated diffusion)是由膜蛋白帮助的扩散。
- 通道蛋白(channel protein)是一个带内衬的孔,让特定的粒子通过。
- 载体蛋白(carrier protein)结合一个分子,然后改变形状,在另一侧把它释放。
- 每个蛋白质都是特异的——形状恰好适合某一种粒子。
Diffusion through a protein · 通过蛋白质扩散
Particles still move down their gradient — but here a membrane protein gives charged or large molecules a way through. · 粒子仍然沿它们的梯度移动——但这里一个膜蛋白给带电或大的分子一条通路。
A channel protein helps diffusion by… · 通道蛋白通过……帮助扩散。
A channel protein is a lined pore; a carrier protein binds a molecule and changes shape to move it. · 通道蛋白是一个带内衬的孔;载体蛋白结合一个分子并改变形状来移动它。
Still passive, still downhill
- Even with a protein's help, the particles move down their gradient.
- No ATP is spent — the protein only provides a route.
- So facilitated diffusion is a form of passive transport.
- It just widens the range of what diffusion can move.
仍然被动,仍然向下
- 即使有蛋白质帮忙,粒子仍然沿它们的梯度向下移动。
- 不花费 ATP——蛋白质只提供一条通路。
- 所以易化扩散是被动运输的一种形式。
- 它只是拓宽了扩散能移动的范围。
Facilitated diffusion is still passive — it uses no ATP. · 易化扩散仍然是被动的——它不用 ATP。
The protein only provides a route; the particles still move down · 下 their gradient, so no ATP is used. · 蛋白质只提供一条通路;粒子仍然沿它们的梯度向下移动,所以不用 ATP。
In facilitated diffusion, particles still move down their concentration ____. · 在易化扩散中,粒子仍然沿它们的浓度____向下移动。
The protein just opens a route; the direction is still down the gradient. · 蛋白质只是打开一条通路;方向仍然是沿梯度向下。
Select all · 所有 true statements about facilitated diffusion. · 选出关于易化扩散的所有正确说法。
It never pumps uphill — that would be active transport. The other three are correct. · 它绝不往上泵——那会是主动运输。其余三条正确。
Facilitated diffusion is not active transport. The protein is only a doorway — the particle still travels down its gradient, and no ATP is used. If it were going uphill, that would be active transport instead.
易化扩散不是主动运输。蛋白质只是一扇门——粒子仍然沿它的梯度向下移动,不用 ATP。如果它是往上走,那就变成主动运输了。
Glucose entering a cell:
- Glucose is large and polar, so it cannot cross the bilayer alone.
- A carrier protein binds it and flips it to the inside.
- Because blood glucose is higher than inside the cell, it still moves down its gradient — passive, no ATP.
葡萄糖进入细胞:
- 葡萄糖又大又极性,所以它不能自己穿过双层。
- 一个载体蛋白结合它,把它翻转到内侧。
- 因为血糖比细胞内部高,它仍然沿它的梯度向下移动——被动,不用 ATP。
Facilitated diffusion lets charged or large molecules cross the membrane using a channel protein (a pore) or a carrier protein (a shape-changing binder). It is still passive: the particles move down their gradient and no ATP is used — the protein just provides the route.
易化扩散让带电或大的分子用通道蛋白(一个孔)或载体蛋白(一个会变形的结合体)穿过膜。它仍然是被动的:粒子沿它们的梯度向下移动,不用 ATP——蛋白质只是提供通路。