細胞の特異化
国際バカロレア · IB Diploma · Biology · HL トピック 14 3:46 英語ナレーション・英語＋中文字幕 burning-in
章
Transcript
A root-hair cell and a red blood cell have different shapes because their functions impose different demands.
根毛细胞和红细胞具有不同的形状，因为它们的功能提出了不同的需求。
Differentiation produces specialized cells through different patterns of gene expression.
分化通过不同的基因表达模式产生特化细胞。
A root-hair extension increases exchange area.
根毛延伸增加了交换面积。
A mammalian red blood cell lacks a nucleus at maturity and contains haemoglobin.
哺乳动物成熟红细胞没有细胞核，含有血红蛋白。
This is a specific adaptation, not a rule for all animal cells.
这是特定适应，并非所有动物细胞的普遍规律。
Differentiation is the development of specialized cell structure and function.
分化是特化细胞结构和功能的发展过程。
Gene expression is the use of genetic information to produce a functional product.
基因表达是利用遗传信息产生功能性产物的过程。
Link a named feature to a mechanism, and then to the function.
将特定特征与机制相联系，再进一步关联到功能。
Increased area can support exchange, but membrane proteins, gradients, and metabolic demand also matter.
表面积增大可支持物质交换，但膜蛋白、浓度梯度及代谢需求同样重要。
Stem cells retain different degrees of developmental potential.
干细胞保留不同程度的发育潜能。
In the lab: Compare scaled drawings of named cells.
在实验室中，比较已命名细胞的按比例绘图。
Label the structure, state the function and explain the causal link.
标注结构，说明功能，并解释因果联系。
Use tissue-specific examples rather than saying every specialized cell has every adaptation.
请使用组织特异性示例，而不是说每种特化细胞都具备所有适应特征。
Known: a spherical model cell has radius 2 units.
已知：一个球形模型细胞的半径为2个单位。
Surface area divided by volume equals 3 divided by r, which is 1.5 per unit.
表面积与体积之比等于3除以r，即每单位1.5。
A radius of 4 gives 0.75 per unit.
半径为4时，该比值为每单位0.75。
Doubling the radius halves this ratio, even though total area increases.
即使总面积增加，将半径加倍也会使该比值减半。
Your turn.
轮到你了。
For a sphere, surface area divided by volume equals 3 over r.
对于球体，表面积除以体积等于三除以r。
Find this ratio when r equals 6 units.
当r等于6个单位时，求这个比值。
Specialization does not usually require a cell to lose most of its genes.
细胞特化通常不需要细胞丢失大部分基因。
The spherical calculation models geometry, but it does not describe every actual cell shape.
球体计算模型描述的是几何形状，但并不能描述所有实际的细胞形态。
Not true: All mature animal cells lack a nucleus.
不正确。 所有成熟的动物细胞都没有细胞核。
Most mature animal cells keep their full genome and nucleus; only a few exceptions, such as mammalian red blood cells, lose the nucleus.
大多数成熟的动物细胞保留其完整的基因组和细胞核。 只有少数例外，如哺乳动物的红细胞，会失去细胞核。
Specialization comes from gene expression, not gene loss.
细胞特化源于基因表达，而非基因丢失。
Differentiation produces specialized cells through different patterns of gene expression.
分化通过不同的基因表达模式产生特化细胞。
Link a named feature to a mechanism and then to the function.
将一个特定特征与机制及其功能联系起来。
Watch for specialization does not usually require a cell to lose most of its genes.
请注意：特化通常不需要细胞丢失大部分基因。
A spherical model cell has a radius of 10 units.
一个球形模型细胞的半径为10个单位。
Use the formula surface area divided by volume equals 3 divided by r to find the ratio.
使用表面积除以体积等于3除以r的公式，求出该比值。
Doubling the radius halves this ratio.
将半径加倍会使该比值减半。
The result is a surface-to-volume ratio of 0.30.
结果是表面积与体积之比为0.30。
For a sphere, surface area over volume is three over the radius.
对球体而言，表面积与体积之比等于三除以半径。
Doubling the radius halves the ratio, so a large cell has less surface for each unit of volume.
半径加倍，比值减半，所以大细胞每单位体积的表面更少。
A spherical cell doubles radius.
一个球形细胞的半径加倍。
Compare area, volume and SA/V factors; explain why total area increasing does not remove exchange constraints.
比较表面积、体积以及表面积与体积比的变化倍数。 解释为什么总表面积的增加并不能消除物质交换的限制。
Doubling the radius multiplies area by 4 and volume by 8, so surface area to volume halves.
半径加倍时，表面积变为 4 倍，体积变为 8 倍，所以表面积与体积之比减半。
Exchange capacity per volume falls in the geometric model; actual cell specialization also involves shape, transport and demand.
在这个几何模型中，单位体积的交换能力下降；实际的细胞特化还涉及形状、运输和需求。
Pause and check yourself. Explain each point on screen in your own words, then change one number in the last example and say which assumption must still hold.
暂停一下，自我检查：用自己的话解释屏幕上的每个要点，再改动最后一个例子中的一个数字，说明哪个假设仍然必须成立。