Sujet 1 : Biologie cellulaire
AQA · GCSE · Biology Sujet 1 22:59 Narration en anglais · sous-titres en anglais et en 中文 au choix
Chapitres
Transcript
Why it matters.
为什么这很重要。
In 1665 the English scientist Robert Hooke published Micrographia, a book of drawings made through his home-built microscope.
1665年，英国科学家罗伯特·胡克出版了《显微图谱》，书中收录了他通过自制显微镜观察后绘制的图画。
When he looked at a thin slice of cork, he saw it was full of tiny empty boxes.
当他观察一片薄软木时，发现里面布满了微小的空盒子。
They reminded him of the small rooms that monks lived in, so he called them "cells".
这些盒子让他想起修道士居住的小房间，于是他把它们称为“细胞”。
Eleven years later, in 1676, the Dutch cloth merchant Antonie van Leeuwenhoek wrote to the Royal Society in London that he had seen "very little animalcules" swimming in a drop of water: the first record of bacteria.
十一年后的1676年，荷兰布商安东尼·范·列文虎克写信给伦敦皇家学会，说他看到水滴中有“非常小的微动物”在游动：这是关于细菌的最早记录。
Every living thing is made of cells, and almost everything in biology, from how a muscle contracts to how an antibiotic works, starts with what happens inside them.
所有生物都由细胞构成，生物学中几乎所有问题，从肌肉如何收缩到抗生素如何起作用，都要从细胞内部发生的事情说起。
In this unit you will: AQA GCSE Biology (8461), topic 4.1 Cell biology, examined on Paper 1.
在本单元中，你将学习：AQA GCSE Biology (8461)，主题4.1细胞生物学，在 Paper 1 中考查。
It includes three required practicals: using a light microscope (RP1), testing antiseptics and antibiotics on bacteria (RP2, biology only) and osmosis in plant tissue (RP3).
它包括三个必修实验：使用光学显微镜 (RP1)、在细菌上测试防腐剂和抗生素 (RP2，仅生物学) 以及植物组织中的渗透作用 (RP3)。
Culturing microorganisms is biology only; content marked (HT) is Higher tier only.
培养微生物仅属于生物学内容；标记为 (HT) 的内容仅属于 Higher 层级。
compare animal, plant and bacterial cells, and link each cell part to its job; explain how cells become specialised, and calculate magnification; culture bacteria safely and test antibiotics (biology only);
比较动物、植物和细菌细胞，并将每个细胞结构与其功能联系起来；解释细胞如何特化，并计算放大倍数；安全地培养细菌并测试抗生素（仅生物学）；
describe the cell cycle, mitosis and the uses of stem cells; explain diffusion, osmosis and active transport, and why large organisms need exchange surfaces.
描述细胞周期、有丝分裂以及干细胞的用途；解释扩散、渗透作用和主动运输，以及大型生物为什么需要交换表面。
Eukaryotic cells, such as animal, plant and yeast cells, keep their genetic material inside a nucleus.
真核细胞，例如动物、植物和酵母菌细胞，将遗传物质保存在细胞核内。
Prokaryotic cells, the bacteria, have no nucleus: their DNA is a single loop in the cytoplasm, and many also have small rings of DNA called plasmids.
原核细胞，也就是细菌，没有细胞核：它们的 DNA 是细胞质中的一个环，许多细菌还有称为质粒的小 DNA 环。
Bacterial cells are much smaller, typically 1 to 5 micrometres long, while most animal and plant cells are 10 to 100 micrometres.
细菌细胞小得多，长度通常为1至5微米，而大多数动物和植物细胞为10至100微米。
Parts of animal and plant cells.
动物和植物细胞的组成部分。
Plant cells also have: Bacterial cells have a cell membrane, cytoplasm, ribosomes and a cell wall (not made of cellulose), but no nucleus, mitochondria or chloroplasts.
植物细胞还有：细菌细胞有细胞膜、细胞质、核糖体和细胞壁（不由纤维素构成），但没有细胞核、线粒体或叶绿体。
A plasmid is a small extra ring of DNA, which often carries genes such as those for antibiotic resistance.
质粒是一个额外的小 DNA 环，常携带抗生素抗性等基因。
Key to the numbers: 1 nucleus, 2 cell membrane, 3 cytoplasm, 4 mitochondrion, 5 ribosome, 6 cell wall, 7 permanent vacuole, 8 chloroplast, 9 DNA loop, 10 plasmid.
数字说明：1细胞核，2细胞膜，3细胞质，4线粒体，5核糖体，6细胞壁，7永久液泡，8叶绿体，9 DNA 环，10质粒。
Worked example 1.
例题1。
A question shows a bacterial cell and a yeast cell.
一道题展示了一个细菌细胞和一个酵母菌细胞。
Name two structures in the yeast cell that are not in the bacterial cell.
说出酵母菌细胞中存在而细菌细胞中不存在的两个结构。
Answer: a nucleus and mitochondria (a permanent vacuole also scores).
答案：细胞核和线粒体（答永久液泡也得分）。
"The yeast cell is more complicated" earns nothing: name the structures.
“酵母菌细胞更复杂”不能得分：要说出结构名称。
The nucleus contains DNA and controls the cell's activities.
细胞核含有 DNA，控制细胞的活动。
The cell membrane controls what enters and leaves the cell.
细胞膜控制物质进出细胞。
The cytoplasm is a jelly where many chemical reactions happen.
细胞质是一种胶状物质，许多化学反应在其中发生。
Each mitochondrion is where aerobic respiration releases energy.
每个线粒体都是有氧呼吸释放能量的场所。
Each ribosome is where proteins are made.
每个核糖体都是合成蛋白质的场所。
a cell wall made of cellulose, which supports the cell;
由纤维素构成的细胞壁，起支撑细胞的作用；
a permanent vacuole filled with cell sap, which keeps the cell firm; in the green parts of the plant, a chloroplast in which photosynthesis happens.
充满细胞液的永久液泡，使细胞保持坚挺；在植物的绿色部分，有进行光合作用的叶绿体。
Root cells are underground and have no chloroplasts.
根细胞位于地下，没有叶绿体。
An animal cell, a plant cell and a bacterial cell, not to scale; the numbers are listed in the key below.
一个动物细胞、一个植物细胞和一个细菌细胞，图中比例不代表实际比例；数字的说明列在下方。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
A bacterial cell and a yeast cell, not to scale (AQA GCSE Biology Paper 1H, June 2025, Figure 10).
一个细菌细胞和一个酵母菌细胞，图中比例不代表实际比例（AQA GCSE Biology Paper 1H，2025年6月，Figure 10）。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
Specialised cells have features that suit their jobs.
特化细胞具有适合其功能的特征。
In an answer, give the feature and then explain how it helps.
答题时，要先说出特征，再解释它如何发挥作用。
Differentiation is the process by which a cell gains the special structures it needs to do one job.
分化是细胞获得完成某一功能所需的特殊结构的过程。
Most animal cells differentiate early in development and then keep their type; cell division in adult animals is mainly for repair and replacement.
大多数动物细胞在发育早期分化，之后保持其类型；成年动物的细胞分裂主要用于修复和替换。
Many plant cells can differentiate throughout the life of the plant.
许多植物细胞在植物的一生中都能分化。
Specialised cells have features that suit their jobs.
特化细胞具有适合其功能的特征。
In an answer, give the feature and then explain how it helps.
答题时，要先说出特征，再解释它如何发挥作用。
Differentiation is the process by which a cell gains the special structures it needs to do one job.
分化是细胞获得完成某一功能所需的特殊结构的过程。
Most animal cells differentiate early in development and then keep their type; cell division in adult animals is mainly for repair and replacement.
大多数动物细胞在发育早期分化，之后保持其类型；成年动物的细胞分裂主要用于修复和替换。
A light microscope uses light and lenses; it magnifies up to about 1500 times.
光学显微镜使用光和透镜；它最多可放大约1500倍。
An electron microscope uses a beam of electrons.
电子显微镜使用电子束。
Electron microscopes have a much greater magnification and resolving power (resolution), the ability to show two points close together as separate.
电子显微镜具有高得多的放大倍数和分辨本领（分辨率），也就是将相距很近的两个点显示为两个独立点的能力。
This is why they revealed ribosomes and the inside of mitochondria, which light microscopes cannot show.
因此，电子显微镜揭示了光学显微镜无法显示的核糖体和线粒体内部结构。
Making a blurred image bigger does not show more detail.
把模糊的图像放大，并不能显示更多细节。
Magnification has no unit.
放大倍数没有单位。
The image size and the real size must be in the same unit before you divide.
相除之前，图像大小和实际大小必须使用相同的单位。
Remember: 1 mm = 1000 µm (micrometres) and 1 µm = 1000 nm (nanometres).
记住：1 mm = 1000 µm（微米），1 µm = 1000 nm（纳米）。
Worked example 2.
例题2。
A cell's image is 4.8 cm long at a magnification of ×1200.
一个细胞的图像长度为4.8 cm，放大倍数为×1200。
Find its real length in micrometres.
求它以微米为单位的实际长度。
4.8 cm = 48 mm = 48 000 mum , so real size = 48 000 over 1200 = 40 mum .
4.8 cm = 48 mm = 48 000 mum，所以实际大小 = 48 000除以1200 = 40 mum。
Worked example 3 (HT).
例题3 (HT)。
A cylindrical structure has volume 24 500 000 nm³ and radius 125 nm.
一个圆柱形结构的体积为24 500 000 nm³，半径为125 nm。
Its image is 4 mm long.
它的图像长度为4 mm。
Find the magnification, using pi = 3.14.
取 pi = 3.14，求放大倍数。
Real length = V over pi r^2 = 24 500 000 over 3.14 times 125^2 = 499.4 nm.
实际长度 = V除以pi r^2 = 24 500 000除以3.14乘以125^2 = 499.4 nm。
Image length = 4 mm = 4 000 000 nm.
图像长度 = 4 mm = 4 000 000 nm。
Magnification = 4 000 000 over 499.4 = 8010, written ×8010 with no unit.
放大倍数 = 4 000 000除以499.4 = 8010，写作×8010，没有单位。
Keep the full value of the real length until the last step.
将实际长度的完整数值保留到最后一步。
Required practical 1: using a light microscope.
必修实验1：使用光学显微镜。
Place a thin specimen, such as onion skin stained with iodine, on a slide under a cover slip.
将薄标本，例如用碘液染色的洋葱表皮，放在载玻片上，并盖上盖玻片。
Start with the lowest-power objective lens, focus with the coarse focus knob, then move to a higher power and use the fine focus.
从最低倍的物镜开始，用粗准焦螺旋调焦，然后换用更高倍的物镜，使用细准焦螺旋。
Draw what you actually see with clear, unshaded outlines, label the structures, and write the magnification (eyepiece × objective) or add a scale bar.
用清晰、不涂阴影的轮廓画出实际看到的内容，标注结构，并写上放大倍数（目镜 × 物镜）或加上比例尺。
A light microscope uses light and lenses; it magnifies up to about 1500 times.
光学显微镜使用光和透镜；它最多可放大约1500倍。
An electron microscope uses a beam of electrons.
电子显微镜使用电子束。
Electron microscopes have a much greater magnification and resolving power (resolution), the ability to show two points close together as separate.
电子显微镜具有高得多的放大倍数和分辨本领（分辨率），也就是将相距很近的两个点显示为两个独立点的能力。
This is why they revealed ribosomes and the inside of mitochondria, which light microscopes cannot show.
因此，电子显微镜揭示了光学显微镜无法显示的核糖体和线粒体内部结构。
Bacteria reproduce by binary fission: one cell splits into two.
细菌通过二分裂繁殖：一个细胞分裂成两个。
In good conditions some bacteria divide as often as every 20 minutes.
在良好条件下，有些细菌最快每20分钟分裂一次。
They can be grown in a liquid nutrient broth or as colonies on agar gel.
它们可以在液体营养肉汤中培养，也可以在琼脂凝胶上培养成菌落。
Worked example 4.
例题4。
One bacterium divides every 20 minutes.
一个细菌每20分钟分裂一次。
How many bacteria are there after 3 hours?
3小时后有多少个细菌？
Number of divisions = 180 div 20 = 9, so the number is 1 times 2^9 = 512.
分裂次数 = 180 div 20 = 9，所以数量为1 times 2^9 = 512。
(HT) In standard form, after 2 hours there are 2^6 = 64 = 6.4 times 10^1 bacteria.
(HT) 用科学记数法表示，2小时后有2^6 = 64 = 6.4 times 10^1个细菌。
This assumes that the bacteria have enough food and space.
这是假设细菌有足够的食物和空间。
Aseptic technique.
无菌操作技术。
Aseptic technique prevents contamination of the culture by unwanted microorganisms.
无菌操作技术可以防止不需要的微生物污染培养物。
Each step has a reason: In school, cultures are kept at 25 °C or below, which reduces the growth of bacteria that could cause disease in humans.
每一步都有其原因：在学校，培养物保持在25 °C或以下，这能减少可能使人生病的细菌的生长。
Hospital laboratories use 37 °C, body temperature, so cultures grow faster.
医院实验室使用37 °C，即体温，使培养物生长得更快。
Required practical 2: antiseptics and antibiotics.
必修实验2：防腐剂和抗生素。
Spread bacteria evenly over agar to make a "lawn".
将细菌均匀涂布在琼脂上，形成“菌苔”。
Put paper discs soaked in different antibiotics or antiseptics on the agar, and one disc soaked in sterile water as a control.
把浸有不同抗生素或防腐剂的纸片放在琼脂上，再放一片浸过无菌水的纸片作为对照。
After incubation, a clear zone forms around a disc where bacteria have been killed or stopped from growing.
培养后，在细菌被杀死或生长受到抑制的纸片周围会形成透明区域。
A bigger zone of inhibition means a more effective substance against that bacterium.
抑菌圈越大，说明该物质对这种细菌越有效。
The control shows that the paper disc alone does not stop growth.
对照表明，纸片本身不会抑制生长。
Worked example 5.
例题5。
In a test, antibiotic C has a small clear zone around it.
在一次测试中，抗生素 C 周围有一个小透明区。
A student says the bacteria are resistant to antibiotic C.
一名学生说细菌对抗生素 C 有抗性。
Explain why the student is wrong.
解释这名学生为什么不对。
A clear zone, even a small one, shows that antibiotic C killed some bacteria or stopped their growth.
透明区即使很小，也表明抗生素 C 杀死了一些细菌或抑制了它们的生长。
If the bacteria were resistant, they would grow right up to the edge of the disc.
如果细菌有抗性，它们就会一直生长到纸片边缘。
Worked example 6.
例题6。
A clear zone has a diameter of 12 mm.
一个透明区的直径为12 mm。
Find its area.
求它的面积。
The radius is 12 div 2 = 6 mm, so the area is pi r^2 = pi times 6^2 = 113 mm² (3 s.f.).
半径为12 div 2 = 6 mm，所以面积为pi r^2 = pi times 6^2 = 113 mm²（3位有效数字）。
Using 12 mm as the radius would give an area four times too large.
如果把12 mm用作半径，得到的面积会是实际面积的四倍。
sterilise the Petri dishes and culture media before use, to kill microorganisms already on them; pass the inoculating loop through a flame before use, to kill microorganisms on it; lift the lid only slightly, so that microorganisms from the air do not fall in;
使用前对培养皿和培养基进行灭菌，以杀死上面已有的微生物；使用前将接种环通过火焰，以杀死上面的微生物；只将盖子稍稍掀起，防止空气中的微生物落入；
secure the lid with tape (but do not seal it all round), so that oxygen can still get in and harmful anaerobic bacteria do not grow; store the dish upside down, so that drops of condensation do not fall onto the agar.
用胶带固定盖子（但不要将四周完全封住），这样氧气仍能进入，有害的厌氧细菌便不会生长；将培养皿倒置存放，防止冷凝水滴落到琼脂上。
Five antibiotics, A to E, and a control disc with no antibiotic (AQA GCSE Biology Paper 1H, June 2023, Figure 4).
五种抗生素，A至E，以及一片不含抗生素的对照纸片（AQA GCSE Biology Paper 1H，2023年6月，Figure 4）。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
Antibiotic A has no clear zone, B a large one and C a small one (AQA GCSE Biology Paper 1H, June 2024, Figure 5).
抗生素 A 没有透明区，B 有一个大的透明区，C 有一个小的透明区（AQA GCSE Biology Paper 1H，2024年6月，Figure 5）。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
A clear zone 12 mm across has a radius of 6 mm.
一个直径为12 mm的透明区，半径为6 mm。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
The nucleus contains chromosomes, long molecules of DNA.
细胞核含有染色体，染色体是长链 DNA 分子。
Each chromosome carries many genes.
每条染色体携带许多基因。
In body cells chromosomes are found in pairs: human body cells have 23 pairs, 46 chromosomes in all.
在体细胞中，染色体成对存在：人体细胞有23对，共46条染色体。
The cell cycle.
细胞周期。
The cell cycle has three stages: 1. The cell grows, makes more ribosomes and mitochondria, and copies its DNA, so that each chromosome becomes two identical copies.
细胞周期有三个阶段：1. 细胞生长，制造更多核糖体和线粒体，并复制 DNA，使每条染色体形成两个完全相同的副本。
2. Mitosis: one set of chromosomes is pulled to each end of the cell, and the nucleus divides.
2. 有丝分裂：一套染色体被拉向细胞的每一端，细胞核分裂。
3. The cytoplasm and cell membrane divide, forming two genetically identical daughter cells.
3. 细胞质和细胞膜分裂，形成两个遗传物质完全相同的子细胞。
Mitosis is used for growth and development, for repairing damage, and for asexual reproduction.
有丝分裂用于生长发育、修复损伤和无性生殖。
Worked example 7.
例题7。
A drug stops the fibres in a cell attaching to the chromosomes.
一种药物阻止细胞中的纤维附着到染色体上。
Explain how this stops the cell dividing.
解释这如何阻止细胞分裂。
Without the fibres, the chromosomes cannot be pulled to each end of the cell, so the nucleus cannot divide into two.
没有纤维，染色体就无法被拉向细胞的两端，因此细胞核无法分裂成两个。
Such a drug can slow the growth of a tumour, where cells divide out of control.
这种药物可以减缓肿瘤的生长，因为肿瘤中的细胞不受控制地分裂。
But it also slows normal dividing cells, which is why some cancer treatments cause hair loss.
但它也会减慢正常细胞的分裂，这就是一些癌症疗法会导致脱发的原因。
The nucleus contains chromosomes, long molecules of DNA.
细胞核含有染色体，染色体是长链 DNA 分子。
Each chromosome carries many genes.
每条染色体携带许多基因。
In body cells chromosomes are found in pairs: human body cells have 23 pairs, 46 chromosomes in all.
在体细胞中，染色体成对存在：人体细胞有23对，共46条染色体。
The cell cycle.
细胞周期。
The cell cycle has three stages:
细胞周期有三个阶段：
Fibres pull the copied chromosomes apart during mitosis (AQA GCSE Biology Paper 1H, June 2024, Figure 9).
有丝分裂过程中，纤维将复制后的染色体拉开（AQA GCSE Biology Paper 1H，2024年6月，Figure 9）。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
A stem cell is undifferentiated: it can divide to make more stem cells and can differentiate into other kinds of cell.
干细胞尚未分化：它可以分裂产生更多干细胞，也可以分化成其他类型的细胞。
Uses.
用途。
Embryonic stem cells might one day replace faulty cells, for example insulin-making cells in diabetes or nerve cells in paralysis.
胚胎干细胞或许有一天能替代功能异常的细胞，例如糖尿病患者产生胰岛素的细胞或瘫痪患者的神经细胞。
In therapeutic cloning, an embryo is made with the same genes as the patient, so its stem cells are not rejected by the patient's immune system.
在治疗性克隆中，培育出与患者基因相同的胚胎，因此其干细胞不会受到患者免疫系统的排斥。
Meristem cells are used to clone plants quickly and cheaply, to save rare species from extinction, or to produce many identical crop plants with useful features such as disease resistance.
分生组织细胞可用于快速、低成本地克隆植物，拯救濒临灭绝的珍稀物种，或大量培育具有抗病等有用特性的相同农作物。
Risks and objections.
风险和反对意见。
Stem cells grown in a laboratory could carry viruses that pass to the patient.
在实验室培养的干细胞可能携带病毒，并传染给患者。
Some people have ethical objections to using embryos: an embryo is destroyed when its stem cells are taken, and some believe an embryo has a right to life.
有些人基于伦理原因反对使用胚胎：提取干细胞时胚胎会被破坏，而有些人认为胚胎有生存权。
For a full answer, give the reason, not just "religion".
要完整作答，应给出原因，不能只说“宗教”。
A stem cell is undifferentiated: it can divide to make more stem cells and can differentiate into other kinds of cell.
干细胞尚未分化：它可以分裂产生更多干细胞，也可以分化成其他类型的细胞。
Uses.
用途。
Embryonic stem cells might one day replace faulty cells, for example insulin-making cells in diabetes or nerve cells in paralysis.
胚胎干细胞或许有一天能替代功能异常的细胞，例如糖尿病患者产生胰岛素的细胞或瘫痪患者的神经细胞。
In therapeutic cloning, an embryo is made with the same genes as the patient, so its stem cells are not rejected by the patient's immune system.
在治疗性克隆中，培育出与患者基因相同的胚胎，因此其干细胞不会受到患者免疫系统的排斥。
Meristem cells are used to clone plants quickly and cheaply, to save rare species from extinction, or to produce many identical crop plants with useful features such as disease resistance.
分生组织细胞可用于快速、低成本地克隆植物，拯救濒临灭绝的珍稀物种，或大量培育具有抗病等有用特性的相同农作物。
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
扩散是粒子从浓度较高的区域向浓度较低的区域的净移动。
Particles move in every direction, but more move down the concentration gradient than up it.
粒子向各个方向运动，但顺浓度梯度移动的粒子比逆浓度梯度移动的多。
Examples are oxygen and carbon dioxide in gas exchange, and urea moving from cells into the blood plasma to be taken to the kidneys.
例子包括气体交换中的氧气和二氧化碳，以及尿素从细胞进入血浆，被运送到肾脏。
Diffusion is faster with a steeper concentration gradient, a higher temperature and a larger membrane surface area.
浓度梯度越陡、温度越高、膜的表面积越大，扩散就越快。
Osmosis is the diffusion of water from a dilute solution to a more concentrated solution through a partially permeable membrane, which lets small water molecules through but not larger solute molecules such as sugar.
渗透作用是水通过半透膜从稀溶液向较浓溶液的扩散；半透膜允许小的水分子通过，却不允许糖等较大的溶质分子通过。
Active transport moves substances from a more dilute solution to a more concentrated solution, against the concentration gradient.
主动运输使物质从较稀的溶液向较浓的溶液移动，逆浓度梯度进行。
It needs energy from respiration.
它需要呼吸作用提供的能量。
Root hair cells use it to absorb each mineral ion from very dilute soil water, and the gut uses it to absorb sugar into the blood when the concentration in the gut is low.
根毛细胞利用主动运输从极稀的土壤水中吸收各种矿物质离子，肠道中糖的浓度较低时，肠道也利用主动运输将糖吸收到血液中。
Required practical 3: osmosis in potato.
必修实验3：马铃薯中的渗透作用。
Cut cylinders of potato of equal size from the same potato.
从同一个马铃薯上切取大小相同的圆柱体。
Blot them dry, weigh each one, and put them in sugar or salt solutions of different concentrations, with the same volume of solution, for the same time and at the same temperature.
吸干它们，分别称重，放入不同浓度的糖溶液或盐溶液中，保持溶液体积、浸泡时间和温度相同。
Then blot and weigh again.
然后再次吸干并称重。
Because the pieces start at slightly different masses, compare them using percentage change: Worked example 8.
由于各块马铃薯的初始质量略有不同，要用百分比变化进行比较：例题8。
A piece of potato goes from 2.5 g to 2.9 g: percentage change = 0.4 over 2.5 times 100 = +16%.
一块马铃薯从2.5 g变为2.9 g：百分比变化 = 0.4除以2.5乘以100 = +16%。
Another goes from 3.0 g to 2.55 g: -0.45 over 3.0 times 100 = -15%.
另一块从3.0 g变为2.55 g：-0.45除以3.0乘以100 = -15%。
Keep the minus sign for a loss.
质量减少时要保留负号。
In distilled water the potato gains mass, because the solution inside its cells is more concentrated and water enters by osmosis.
在蒸馏水中，马铃薯的质量增加，因为其细胞内的溶液浓度更高，水通过渗透作用进入细胞。
In a concentrated solution it loses mass, because water leaves.
在浓溶液中，它的质量会减少，因为水流出。
Where the graph crosses zero, there is no net movement of water: the solution outside has the same concentration as the cell sap.
图线与零线相交的地方，水没有净移动：外部溶液与细胞液的浓度相同。
Water molecules still move both ways, but equally.
水分子仍然双向移动，但移动量相等。
Worked example 9.
例题9。
Using the graph, explain why the mass of potato decreases in a 0.6 mol/dm³ solution, and why it decreases more in a 1.0 mol/dm³ solution.
利用图像解释为什么马铃薯在0.6 mol/dm³溶液中质量会减少，以及为什么在1.0 mol/dm³溶液中减少得更多。
In 0.6 mol/dm³ the solution outside is more concentrated than the cell sap, so water leaves the cells by osmosis.
在0.6 mol/dm³溶液中，外部溶液比细胞液浓，因此水通过渗透作用离开细胞。
In 1.0 mol/dm³ the concentration gradient is steeper, so more water leaves in the same time.
在1.0 mol/dm³溶液中，浓度梯度更陡，所以在相同时间内流出的水更多。
Diffusion is the net movement of particles from an area of higher concentration to an area of lower concentration.
扩散是粒子从浓度较高的区域向浓度较低的区域的净移动。
Particles move in every direction, but more move down the concentration gradient than up it.
粒子向各个方向运动，但顺浓度梯度移动的粒子比逆浓度梯度移动的多。
Examples are oxygen and carbon dioxide in gas exchange, and urea moving from cells into the blood plasma to be taken to the kidneys.
例子包括气体交换中的氧气和二氧化碳，以及尿素从细胞进入血浆，被运送到肾脏。
Diffusion is faster with a steeper concentration gradient, a higher temperature and a larger membrane surface area.
浓度梯度越陡、温度越高、膜的表面积越大，扩散就越快。
Diffusion, osmosis and active transport compared in three panels.
三幅图分别比较扩散、渗透作用和主动运输。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
Mean change in mass of potato in grams against solution concentration (AQA GCSE Biology Paper 1H, June 2024, Figure 4).
马铃薯质量的平均变化量，单位为克，与溶液浓度的关系（AQA GCSE Biology Paper 1H，2024年6月，Figure 4）。
Read the axes and units first.
先看坐标轴和单位。
A small single-celled organism can get all the oxygen it needs by diffusion through its surface.
小型单细胞生物可以通过表面的扩散获得所需的全部氧气。
A large organism cannot, because it has much less surface for each unit of volume, and its inner cells are far from the surface.
大型生物则不能，因为它每单位体积所对应的表面积小得多，而且内部细胞离表面很远。
This is shown by the surface area to volume ratio.
这可以用表面积与体积之比来说明。
Worked example 10.
例题10。
A cube of side 2 mm has surface area 6 times 2^2 = 24 mm² and volume 2^3 = 8 mm³, a ratio of 24 : 8 = 3 : 1.
边长为2 mm的立方体，表面积为6 times 2^2 = 24 mm²，体积为2^3 = 8 mm³，比值为24 : 8 = 3 : 1。
A cube of side 4 mm has surface area 96 mm² and volume 64 mm³, a ratio of 1.5 : 1.
边长为4 mm的立方体，表面积为96 mm²，体积为64 mm³，比值为1.5 : 1。
Doubling the side multiplies the area by 4 but the volume by 8, so the ratio halves.
边长加倍，面积变为4倍，体积却变为8倍，因此比值减半。
The larger cube has more surface in total, but less surface for each mm³ inside it.
较大的立方体总表面积更大，但内部每mm³对应的表面积更小。
So a multicellular organism needs exchange surfaces and a transport system, while a single-celled organism does not.
因此，多细胞生物需要交换表面和运输系统，而单细胞生物不需要。
Good exchange surfaces have: Examples are the alveoli in the lungs, surrounded by capillaries; the villi of the small intestine; fish gills; and plant roots and leaves.
良好的交换表面具有：例子包括周围有毛细血管的肺泡、小肠绒毛、鱼鳃，以及植物的根和叶。
a large surface area, so more substance crosses at once; a thin membrane, so the diffusion path is short; (in animals) a good blood supply, which carries substances away and keeps the gradient steep; (for gas exchange) ventilation, which brings in fresh air or water.
较大的表面积，使更多物质能同时通过；薄膜，使扩散路径短；（在动物中）良好的血液供应，将物质运走并保持较陡的浓度梯度；（对于气体交换）通气，带来新鲜空气或水。
Two cubes showing how doubling the side halves the surface-area-to-volume ratio.
两个立方体展示了边长加倍如何使表面积与体积之比减半。
Match each part of the diagram to the text.
将图中的各部分与文字对应起来。
AQA, GCSE Biology (8461) specification, section 4.1 Cell biology, and the required practical handbook.
AQA，GCSE Biology (8461) 课程标准，4.1节细胞生物学，以及必修实验手册。
R. Hooke, Micrographia (London, 1665), Observation XVIII, on cork. A.
R. 胡克，《显微图谱》（伦敦，1665年），关于软木的第十八项观察。
van Leeuwenhoek, letter to the Royal Society of 9 October 1676, Philosophical Transactions 12 (1677).
A. 范·列文虎克，1676年10月9日致皇家学会的信，《哲学汇刊》第12卷（1677年）。
AQA, GCSE Biology Paper 1 Higher (June 2023, 2024 and 2025), the antibiotic, cell division and osmosis questions, adapted.
AQA，GCSE Biology Paper 1 Higher（2023年、2024年和2025年6月），改编自抗生素、细胞分裂和渗透作用试题。
Saying all plant cells have chloroplasts; root cells do not.
说所有植物细胞都有叶绿体；根细胞没有。
Saying bacteria have no ribosomes or no cell wall; they have both.
说细菌没有核糖体或没有细胞壁；它们两者都有。
Dividing image size by real size without first changing to the same unit, or giving magnification a unit.
没有先换算成相同单位就用图像大小除以实际大小，或者给放大倍数加上单位。
Calling the water disc in RP2 a "control variable"; it is a control.
将 RP2 中的水纸片称为“控制变量”；它是对照。
Using the diameter instead of the radius in pi r^2.
在 pi r^2 中使用直径而不是半径。
Saying "water molecules stop moving" when there is no net osmosis.
没有净渗透时，说“水分子停止移动”。
Writing that active transport moves substances down the concentration gradient.
写主动运输使物质顺浓度梯度移动。
Saying a larger cube has a larger surface area to volume ratio.
说较大的立方体具有较大的表面积与体积之比。
Eukaryotic cell: a cell with its DNA inside a nucleus.
真核细胞：DNA 位于细胞核内的细胞。
Prokaryotic cell: a bacterial cell, with no nucleus.
原核细胞：没有细胞核的细菌细胞。
Differentiation: the process by which a cell becomes specialised.
分化：细胞变得特化的过程。
Magnification: how many times bigger the image is than the real object.
放大倍数：图像比实际物体大多少倍。
Aseptic technique: methods that stop unwanted microorganisms contaminating a culture.
无菌操作技术：防止不需要的微生物污染培养物的方法。
Mitosis: the division of the nucleus that makes two identical nuclei.
有丝分裂：细胞核分裂形成两个相同细胞核的过程。
Stem cell: an undifferentiated cell that can make more stem cells and other cell types.
干细胞：能产生更多干细胞和其他类型细胞的未分化细胞。
Diffusion: the net movement of particles from higher to lower concentration.
扩散：粒子从高浓度向低浓度的净移动。
Osmosis: the diffusion of water across a partially permeable membrane from a dilute to a concentrated solution.
渗透作用：水通过半透膜从稀溶液向浓溶液的扩散。
Active transport: movement against a concentration gradient, using energy from respiration.
主动运输：利用呼吸作用释放的能量，逆浓度梯度进行的移动。
1. Name three structures found in plant cells but not in animal cells.
1. 说出植物细胞有而动物细胞没有的三个结构。
2. An image is 30 mm long and the magnification is ×500.
2. 图像长度为30 mm，放大倍数为×500。
Find the real length in µm.
求以µm为单位的实际长度。
3.
3.
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