Membrane Permeability · 膜的通透性
| English | 中文 | Pinyin · 拼音 |
|---|---|---|
| diffusion/dɪˈfjuːʒn/ | 扩散 | kuò sàn |
| concentration gradient/ˌkɒnsənˈtreɪʃn ˈɡreɪdɪənt/ | 浓度梯度 | nóng dù tī dù |
| passive/ˈpæsɪv/ | 被动的 | bèi dòng de |
Crossing without effort
- Some things enter and leave a cell all by themselves, with no energy spent.
- Oxygen drifts in; carbon dioxide drifts out — no pumping needed.
- This free movement is called diffusion.
- It is the simplest way a substance can cross the membrane.
不费力地穿过
- 有些东西完全靠自己进出细胞,不花费能量。
- 氧气飘进来;二氧化碳飘出去——不需要泵送。
- 这种自由的移动叫做扩散。
- 它是一种物质穿过膜最简单的方式。
Diffusion: high to low
- Diffusion 扩散 is the net movement of particles from where they are crowded to where they are sparse.
- Particles are always moving randomly, so they spread out on their own.
- The overall drift is from high concentration to low.
- Given time, the particles end up evenly spread.
扩散:从高到低
- 扩散(diffusion)是粒子从拥挤的地方到稀疏的地方的净移动。
- 粒子总是在随机运动,所以它们自己散开。
- 总体的漂移是从高浓度到低浓度。
- 给足时间,粒子最终会均匀分布。
In diffusion, particles move… · 在扩散中,粒子……移动。
Diffusion · 扩散 is the net movement of particles down their concentration gradient — high to low. · 扩散是粒子沿它们的浓度梯度的净移动——从高到低。
The concentration gradient
- The difference in concentration between two places is the concentration gradient 浓度梯度.
- A steeper gradient makes diffusion faster.
- As the two sides even out, the gradient shrinks and diffusion slows.
- When both sides are equal, net movement stops.
浓度梯度
- 两个地方之间浓度的差异是浓度梯度(concentration gradient)。
- 更陡的梯度让扩散更快。
- 随着两侧变得均匀,梯度缩小,扩散变慢。
- 当两侧相等时,净移动停止。
Diffusion across a membrane · 跨膜扩散
Drag the concentrations. Particles diffuse down their gradient until both sides are equal. · 拖动浓度。粒子沿它们的梯度扩散,直到两侧相等。
The difference in concentration between two regions is the concentration ____. · 两个区域之间浓度的差异是浓度 ____。
A steeper concentration gradient makes diffusion faster. · 更陡的浓度梯度让扩散更快。
Passive: no energy needed
- Diffusion is passive 被动的 — the cell spends no ATP on it.
- The particles' own random motion does all the work.
- This is why simple gases cross the membrane for free.
- Warmth, a big surface, and a thin membrane all speed it up.
被动:不需要能量
- 扩散是被动(passive)的——细胞不为它花费 ATP。
- 粒子自己的随机运动做了所有的工作。
- 这就是简单气体免费穿过膜的原因。
- 温暖、大表面和薄膜都加快它。
Diffusion is passive — it needs no energy from the cell. · 扩散是被动的——它不需要细胞的能量。
Diffusion is passive: particles move on their own random motion, so the cell spends no ATP. · 扩散是被动的:粒子靠自己的随机运动移动,所以细胞不花费 ATP。
Which change makes diffusion across a membrane faster · 更快? · 哪个变化让跨膜扩散更快?
A steeper gradient (plus a thin membrane, big area, and warmth) speeds diffusion. · 更陡的梯度(加上薄膜、大面积和温暖)加快扩散。
Select all · 所有 true statements about diffusion. · 选出关于扩散的所有正确说法。
Diffusion goes high → low, never the reverse on its own. The other three are correct. · 扩散是从高 → 低,不会自己反过来。其余三条正确。
When both sides are equal, the particles do not stop moving. They keep darting about — but just as many cross each way, so there is no net change. Equal concentration means no net movement, not no movement at all.
当两侧相等时,粒子并不停止移动。它们继续四处乱窜——但每个方向穿过的数量一样多,所以没有净变化。浓度相等意味着没有净移动,而不是完全没有移动。
Oxygen into your blood:
- Air in the lungs is rich in oxygen; blood arriving is low in it.
- That gradient drives oxygen to diffuse across the thin lung wall into the blood.
- No energy is spent — the gradient does the work, all by diffusion.
氧气进入你的血液:
- 肺里的空气富含氧气;到达的血液氧气少。
- 那个梯度驱动氧气跨过薄薄的肺壁扩散进血液。
- 不花费能量——梯度做了工作,全靠扩散。
Diffusion is the net, passive movement of particles down a concentration gradient — from high to low — needing no ATP. A steeper gradient, a thinner membrane, and a larger area all speed it up. Net movement stops when both sides are equal, though particles keep moving.
扩散是粒子沿浓度梯度的净的、被动的移动——从高到低——不需要 ATP。更陡的梯度、更薄的膜和更大的面积都加快它。两侧相等时净移动停止,尽管粒子仍在移动。