IGCSE Edexcel Biology: Cell Structure and Organisation | IGCSE Edexcel 生物：细胞结构与组织

📚 IGCSE Edexcel Biology: Cell Structure and Organisation | IGCSE Edexcel 生物：细胞结构与组织

Understanding the structure of cells is the foundation of all IGCSE Biology. Every living organism is made of cells, and the way these cells are organised determines how life functions at every level. In this revision guide, we will explore eukaryotic and prokaryotic cells, the functions of key organelles, specialised cells, levels of organisation, and the mathematics of microscopy.

理解细胞结构是 IGCSE 生物学的全部基础。每一种生物体都由细胞构成，而细胞的组织方式决定了生命在各个层面上如何运作。在本复习指南中，我们将探讨真核细胞与原核细胞、关键细胞器的功能、特化细胞、组织层级以及显微术中的数学计算。

1. The Cell Theory | 细胞学说

The cell theory is a unifying biological idea that summarises three main principles. First, all living organisms are composed of one or more cells. Second, the cell is the basic unit of structure and organisation in all organisms. Third, all cells arise from pre-existing cells through cell division.

细胞学说是一个统一的生物学基本观点，包含三条主要原则。第一，所有生物体由一种或多种细胞构成。第二，细胞是生物体结构和组织的基本单位。第三，所有细胞都通过细胞分裂来自已有的细胞。

This theory applies to all life forms, from single-celled bacteria to complex multicellular animals like humans. It also explains why viruses are not considered living cells, because viruses cannot reproduce on their own and do not have a cellular structure.

这一学说适用于所有生命形式，从单细胞细菌到人类这样的复杂多细胞动物。它也能解释为什么病毒不被视为细胞，因为病毒无法自行繁殖，也不具有细胞结构。

For the Edexcel IGCSE exam, you need to be able to state these principles clearly and use the idea of cell theory to distinguish living organisms from non-living structures.

在 Edexcel IGCSE 考试中，你需要清晰陈述这些原则，并能运用细胞学说的思想区分生物体与非生物结构。

2. Animal Cells and Plant Cells | 动物细胞与植物细胞

Animal cells and plant cells are both eukaryotic cells, meaning they have a true nucleus enclosed by a membrane. However, they show important structural differences that you must be able to draw and label from memory.

动物细胞和植物细胞都属于真核细胞，意味着它们具有由膜包被的真正细胞核。然而，它们之间存在重要的结构差异，你需要能够凭记忆画出并标注。

Typical animal cells contain the following structures: the cell membrane, cytoplasm, nucleus, mitochondria, and ribosomes. Many animal cells also contain small vacuoles, but these are usually not permanent or large.

典型的动物细胞包含以下结构：细胞膜、细胞质、细胞核、线粒体和核糖体。许多动物细胞还含有小液泡，但这些液泡通常不是永久性的，也不大。

Typical plant cells contain all of the above, plus a cell wall made of cellulose, a permanent large vacuole, and chloroplasts in the parts of the plant that carry out photosynthesis. The cell wall provides strength and prevents the cell from bursting when water enters by osmosis.

典型的植物细胞包含上述所有结构，此外还有由纤维素构成的细胞壁、持久性大液泡，以及植物进行光合作用部位所含的叶绿体。细胞壁提供强度，并在水分通过渗透作用进入细胞时防止细胞胀破。

When drawing cells for exams, always label the cell membrane as a thin line, the cell wall as a thick outer line, and the chloroplast as an oval containing internal membranes. Accuracy of proportion matters.

在考试中画细胞图时，务必把细胞膜画成细线，细胞壁画成粗外线，叶绿体画成含有内部膜结构的椭圆形。比例准确很重要。

3. Organelles and Their Functions | 细胞器及其功能

Each organelle performs a specialised job inside the cell. You need to connect each structure to its function with confidence. The most tested organelles are the nucleus, cytoplasm, cell membrane, mitochondria, ribosomes, chloroplasts, and vacuole.

每种细胞器在细胞内执行专门的功能。你需要自信地将每种结构与功能对应起来。最常考到的细胞器包括细胞核、细胞质、细胞膜、线粒体、核糖体、叶绿体和液泡。

Nucleus – controls all cell activities and contains genetic material in the form of DNA. It directs protein synthesis and cell division.

细胞核 – 控制细胞的所有活动，并以 DNA 形式携带遗传物质。它指导蛋白质合成和细胞分裂。
Cytoplasm – a jelly-like liquid where most metabolic reactions occur. It is the site of many enzyme-catalysed reactions.

细胞质 – 一种凝胶状液体，是大多数代谢反应发生的场所，也是许多酶催化反应的位点。
Cell membrane – controls what enters and leaves the cell. It is partially permeable and holds the cell contents together.

细胞膜 – 控制物质进出细胞。它具有部分通透性，并将细胞内容物维持在内部。
Mitochondria – the site of aerobic respiration. They release energy from glucose in the form of ATP.

线粒体 – 有氧呼吸的场所。它们从葡萄糖中释放能量，生成 ATP。
Ribosomes – the site of protein synthesis. They are found free in the cytoplasm or attached to the endoplasmic reticulum.

核糖体 – 蛋白质合成的场所。它们游离于细胞质中，或附着在内质网上。
Chloroplasts – found in plant cells, they absorb light energy for photosynthesis. They contain a green pigment called chlorophyll.

叶绿体 – 存在于植物细胞中，吸收光能进行光合作用。它们含有称为叶绿素的绿色色素。
Permanent vacuole – found in plant cells, it contains cell sap and helps support the plant by maintaining turgor pressure.

持久液泡 – 存在于植物细胞中，含有细胞液，并通过维持膨压来支撑植物。
Cell wall – found in plant cells, made of cellulose. It provides structural support and prevents bursting.

细胞壁 – 存在于植物细胞中，由纤维素构成。它提供结构支撑并防止细胞胀破。

Remember that animal cells lack chloroplasts and a true cell wall, so they cannot photosynthesise and they rely on the cell membrane alone to control transport.

请记住，动物细胞没有叶绿体和真正的细胞壁，因此不能进行光合作用，只能依靠细胞膜来控制物质运输。

4. Prokaryotic Cells vs Eukaryotic Cells | 原核细胞与真核细胞

Prokaryotic cells are the cells of bacteria. They are much smaller and simpler than eukaryotic cells. The key difference is that prokaryotic cells do not have a nucleus. Their genetic material floats freely in the cytoplasm as a circular DNA molecule called a plasmid.

原核细胞是细菌的细胞。它们比真核细胞小得多、简单得多。关键区别在于原核细胞没有细胞核。它们的遗传物质以称为质粒的环状 DNA 分子形式游离在细胞质中。

Prokaryotic cells also lack mitochondria and chloroplasts. Instead of mitochondria, respiration takes place in the cell membrane, and photosynthesis in photosynthetic bacteria occurs in the cytoplasm or in internal membranes.

原核细胞也没有线粒体和叶绿体。有氧呼吸不在线粒体中进行，而是在细胞膜上进行；光合细菌的光合作用则发生在细胞质或内部膜结构中。

Another distinguishing feature is the cell wall. Prokaryotic cell walls are not made of cellulose; they are made of peptidoglycan. Some prokaryotic cells also have a capsule, a flagellum, and small hairlike structures called pili.

另一个区别特征是细胞壁。原核细胞的细胞壁不是由纤维素构成的，而是由肽聚糖构成。一些原核细胞还有荚膜、鞭毛和称为菌毛的细小毛状结构。

The table below summarises the main differences for quick revision.

下表总结了主要区别，便于快速复习。

Feature	Prokaryotic cell	Eukaryotic cell
Nucleus	Absent	Present
Size	Small (0.1–5 μm)	Large (10–100 μm)
Genetic material	Circular plasmid DNA	Linear DNA in nucleus
Mitochondria	Absent	Present
Chloroplasts	Absent	Present in plants
Ribosomes	Small (70S)	Large (80S)
Cell wall material	Peptidoglycan	Cellulose in plants; none in animals

In the exam, if you are asked to name one feature of a bacterial cell that is not present in an animal cell, you should say plasmid or capsule or peptidoglycan cell wall.

在考试中，如果要求你说出一种细菌细胞有而动物细胞没有的特征，你应该回答质粒、荚膜或肽聚糖细胞壁。

5. Specialised Cells | 特化细胞

In multicellular organisms, cells become specialised for particular functions. This process is called differentiation. Specialised cells have different shapes and numbers of organelles depending on their role.

在多细胞生物中，细胞会特化执行特定功能，这个过程称为分化。特化细胞的形状和细胞器数量会根据其功能而有所不同。

Common examples you need to know include red blood cells, root hair cells, sperm cells, palisade mesophyll cells, and nerve cells. For each, you should be able to explain how its structure is adapted to its function.

你需要掌握的常见例子包括红细胞、根毛细胞、精子细胞、栅栏叶肉细胞和神经细胞。对于每一种，你都应该能解释其结构如何适应功能。

Red blood cells – biconcave disc shape increases surface area for oxygen absorption. They contain haemoglobin and lack a nucleus, allowing more space for oxygen carriage.

红细胞 – 双凹圆盘形增加了吸收氧气的表面积。它们含有血红蛋白，没有细胞核，为携带氧气腾出更多空间。
Root hair cells – long hair-like extension increases surface area for absorbing water and mineral ions. They have many mitochondria to provide energy for active transport.

根毛细胞 – 细长的毛状突起增加了吸收水分和矿质离子的表面积。它们含有许多线粒体，为主动运输提供能量。
Sperm cells – a long tail (flagellum) helps them swim. Lots of mitochondria provide energy for movement, and the acrosome contains enzymes to digest the egg membrane.

精子细胞 – 长尾（鞭毛）帮助其游动。大量线粒体提供运动所需能量，顶体中含有消化卵细胞膜的酶。
Palisade mesophyll cells – packed with chloroplasts to maximise photosynthesis. They are tall and column-shaped, positioned near the leaf surface.

栅栏叶肉细胞 – 富含叶绿体以最大化光合作用效率。它们呈长柱状，位于靠近叶表面的位置。
Nerve cells – long axon carries electrical impulses over long distances. Branched dendrites connect with other nerve cells.

神经细胞 – 长轴突在长距离上传导电脉冲。分支状树突与其他神经细胞形成连接。

The exam often asks you to “use one feature of the cell to explain how it is adapted.” Always link structure directly to function, using specific terms like surface area, mitochondria, or haemoglobin.

考试经常要求你“利用细胞的一个特征解释其如何适应功能”。务必把结构与功能直接联系起来，使用表面积、线粒体或血红蛋白等具体术语。

6. Levels of Organisation | 组织的层级

Cells are not isolated. They work together in a hierarchy of biological organisation. The correct order is cell, tissue, organ, organ system, and organism.

细胞并非孤立存在。它们按照生物组织的层级结构协同工作。正确的顺序是细胞、组织、器官、器官系统和生物体。

A tissue is a group of cells with a similar structure that work together to perform a shared function. For example, muscle tissue, xylem tissue, and phloem tissue are all made of specialised cells.

组织是一群结构相似、共同执行相同功能的细胞。例如，肌肉组织、木质部组织和韧皮部组织都是由特化细胞构成的。

An organ is a structure made of different tissues working together. For example, the stomach contains muscle tissue to churn food, glandular tissue to secrete digestive juices, and epithelial tissue to line its inner surface.

器官是由不同组织协同工作构成的结构。例如，胃包含肌肉组织来搅拌食物、腺体组织分泌消化液，以及上皮组织衬覆其内表面。

An organ system is a group of organs that work together to perform a major function. The digestive system, respiratory system, and circulatory system are common examples.

器官系统是一组器官共同执行一项重要功能。消化系统、呼吸系统和循环系统都是常见例子。

A helpful way to remember the order is: Cell → Tissue → Organ → Organ System → Organism.

一个帮助记忆顺序的好方法是：细胞 → 组织 → 器官 → 器官系统 → 生物体。

When you answer a question about organisation, always name a specific tissue and a specific organ to demonstrate full understanding.

在回答组织层级问题时，务必说出具体的组织和具体的器官，以展示完整理解。

7. Microscopy and Magnification | 显微术与放大倍数

To study cells, we use microscopes. Light microscopes can magnify up to about ×1500 and are used to see cell walls, nuclei, mitochondria, and chloroplasts. Electron microscopes can magnify much more, up to ×500,000, and allow us to see ribosomes, membranes, and viruses.

为了研究细胞，我们使用显微镜。光学显微镜最多可放大约 1500 倍，用于观察细胞壁、细胞核、线粒体和叶绿体。电子显微镜可放大大得多，可达 50 万倍，使我们能看到核糖体、膜和病毒。

In practical questions, you need to use the magnification formula. The equation is usually remembered by the triangle: magnification equals image size divided by actual size.

在实验题中，你需要使用放大倍数公式。通常可用三角形记忆：放大倍数等于图像尺寸除以实际尺寸。

Magnification = Image size ÷ Actual size

放大倍数 = 图像尺寸 ÷ 实际尺寸

You can rearrange the formula to find actual size: Actual size = Image size ÷ Magnification. You can also find image size by multiplying actual size by magnification.

你可以重新排列公式求实际尺寸：实际尺寸 = 图像尺寸 ÷ 放大倍数。也可以用实际尺寸乘以放大倍数求出图像尺寸。

Always check your units before substituting into the formula. Convert everything to the same unit, usually millimetres (mm), micrometres (μm), or nanometres (nm).

在代入公式前务必检查单位。将所有数值换算为相同单位，通常为毫米（mm）、微米（μm）或纳米（nm）。

Common conversions you need to know:

你需要掌握的常见换算关系：

1 cm = 10 mm

1 厘米 = 10 毫米
1 mm = 1000 μm

1 毫米 = 1000 微米
1 μm = 1000 nm

1 微米 = 1000 纳米

Suppose a cell measures 80 mm in a diagram under a magnification of ×2000. To find the actual size, first convert 80 mm to μm: 80 mm = 80,000 μm. Then divide by magnification: 80,000 ÷ 2000 = 40 μm. The actual cell is 40 μm long.

假设某细胞在放大 2000 倍的图像中测得 80 mm。求实际尺寸时，先将 80 mm 转换为 μm：80 mm = 80,000 μm。然后除以放大倍数：80,000 ÷ 2000 = 40 μm。所以该细胞实际长度为 40 μm。

Remember that an electron microscope gives much higher resolution than a light microscope. Resolution is the ability to distinguish two separate points that are very close together.

请记住，电子显微镜的分辨率远高于光学显微镜。分辨率是指区分彼此非常接近的两个点的能力。

8. Differences Between Animal and Plant Cells | 动物细胞与植物细胞的区别

This is one of the most commonly tested areas in IGCSE Biology. You must be able to recall all the structures present in a plant cell but absent in an animal cell, and vice versa.

这是 IGCSE 生物中最常考查的内容之一。你必须能够回忆出植物细胞有而动物细胞没有的结构，以及相反情况。

Structure	Animal cell	Plant cell
Cell wall	Absent	Present (cellulose)
Chloroplast	Absent	Present
Large vacuole	Absent or small and temporary	Present and permanent
Nucleus	Present	Present
Mitochondria	Present	Present
Ribosomes	Present	Present
Cell membrane	Present	Present
Cytoplasm	Present	Present

You may also be asked to identify cell types from a diagram. Look for the presence of a cell wall and chloroplast to identify a plant cell. Look for an irregular shape and absence of cell wall to identify an animal cell.

你还可能被要求根据图示识别细胞类型。观察是否有细胞壁和叶绿体来判断植物细胞；观察形状不规则且没有细胞壁来判断动物细胞。

9. Common Misconceptions and Exam Tips | 常见误区与考试技巧

Many students lose marks because of small but important mix-ups. One common error is writing that the cell wall “controls what enters and leaves the cell.” That is the role of the cell membrane, not the cell wall. The cell wall only provides support and allows water and solutes to pass through freely.

许多学生因为细小但重要的混淆而丢分。一个常见错误是写“细胞壁控制物质进出细胞”。那是细胞膜的功能，而不是细胞壁的功能。细胞壁只提供支撑，并让水和溶质自由通过。

Another mistake is saying that mitochondria “make energy.” They do not make energy; they release energy from glucose in a form usable by the cell. Energy is never created or destroyed.

另一个错误是写“线粒体制造能量”。线粒体并不制造能量，而是从葡萄糖中释放细胞可利用形式的能量。能量不会凭空产生或消失。

Students also confuse resolution with magnification. A high magnification without good resolution will show a blurry image. Electron microscopes provide both high magnification and high resolution.

学生也常把分辨率与放大倍数混淆。放大倍数高而分辨率低，只会得到模糊的图像。电子显微镜同时提供高放大倍数和高分辨率。

In calculation questions, always show your working and include units. If the answer asks for μm, make sure your final answer uses μm, not mm or cm.

在计算题中，一定要写出过程并包含单位。如果题目要求以 μm 作答，确保最终答案使用 μm，而不是 mm 或 cm。

Finally, do not leave definitions vague. Use precise biological vocabulary such as “partially permeable membrane”, “aerobic respiration”, and “protein synthesis” to gain full marks.

最后，不要让定义含糊不清。使用准确的生物学术语，如“部分通透性膜”“有氧呼吸”和“蛋白质合成”，以获得满分。

By mastering the structure of cells, the functions of organelles, and the differences between prokaryotic and eukaryotic cells, you will have a strong foundation for the rest of your IGCSE Biology course. Keep practising with past paper questions and always connect structure to function.

通过掌握细胞结构、细胞器功能以及原核细胞与真核细胞的区别，你将为 IGCSE 生物课程的其余部分打下坚实基础。持续练习往年真题，并始终将结构与功能联系起来。

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IGCSE Edexcel Biology: Cell Structure and Organisation | IGCSE Edexcel 生物：细胞结构与组织