GCSE WJEC Biology: Cell Structure Key Points | GCSE WJEC 生物：细胞结构 考点精讲

📚 GCSE WJEC Biology: Cell Structure Key Points | GCSE WJEC 生物：细胞结构 考点精讲

Understanding cell structure is fundamental to GCSE WJEC Biology. This article covers key concepts including organelles, differences between cell types, microscopy, cell specialisation, and transport processes. By working through these topics, you will consolidate your knowledge and be better prepared for exam questions on cell biology.

了解细胞结构是 GCSE WJEC 生物的基础。本文涵盖关键概念，包括细胞器、不同细胞类型之间的差异、显微镜技术、细胞特化以及物质运输过程。通过系统学习这些主题，你将巩固知识，并在细胞生物学的考试中更有把握。

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1. What is a Cell? | 什么是细胞？

A cell is the basic structural and functional unit of all living organisms. Some organisms are unicellular (made of one cell, e.g. bacteria), while others are multicellular (made of many cells, e.g. humans and plants). Cells can be broadly classified into eukaryotic cells (with a true nucleus and membrane-bound organelles) and prokaryotic cells (lacking a nucleus and membrane-bound organelles). The cell theory states that all living things are composed of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells.

细胞是所有生物体结构和功能的基本单位。有些生物是单细胞的（由一个细胞构成，如细菌），而其他生物是多细胞的（由许多细胞构成，如人类和植物）。细胞可大致分为真核细胞（具有真正的细胞核和膜包被的细胞器）和原核细胞（没有细胞核和膜包被的细胞器）。细胞学说指出：所有生物都是由细胞组成的，细胞是生命的基本单位，并且所有细胞都来源于已存在的细胞。

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2. Animal Cells and Their Organelles | 动物细胞及其细胞器

Animal cells are typical eukaryotic cells. They are bounded by a cell membrane and contain several organelles suspended in a jelly-like cytoplasm. Below are the key structures you must know for your WJEC exam, together with their functions.

动物细胞是典型的真核细胞。它们由细胞膜包围，内含悬浮在胶冻状细胞质中的多种细胞器。以下是你必须掌握的 WJEC 考试关键结构及其功能。

Cell membrane: A very thin, partially permeable layer that controls which substances enter and leave the cell. It is composed mainly of phospholipids and proteins.

细胞膜： 一层极薄的部分通透膜，控制物质进出细胞。主要由磷脂和蛋白质组成。

Nucleus: The largest organelle, surrounded by a nuclear envelope with pores. It contains the cell’s genetic material (DNA) arranged as chromatin, and controls all cellular activities, including cell division and protein synthesis.

细胞核： 最大的细胞器，由带有核孔的核膜包围。内含以染色质形式存在的遗传物质（DNA），控制所有细胞活动，包括细胞分裂和蛋白质合成。

Cytoplasm: A jelly-like substance where most of the cell’s metabolic reactions occur. It contains water, dissolved solutes and organelles.

细胞质： 一种胶状物质，大多数细胞的代谢反应在此进行。其中含有水、溶解的溶质和细胞器。

Mitochondria (singular: mitochondrion): Oval-shaped organelles with a double membrane; the inner membrane is folded into cristae. They are the site of aerobic respiration, releasing energy in the form of ATP.

线粒体（单数 mitochondrion）： 具有双层膜的椭圆形细胞器；内膜向内折叠形成嵴。它们是有氧呼吸的场所，以 ATP 的形式释放能量。

Ribosomes: Tiny organelles made of RNA and protein. They are responsible for protein synthesis. In eukaryotic cells, ribosomes can be found free in the cytoplasm or attached to the rough endoplasmic reticulum (although the ER is not required at GCSE).

核糖体： 由 RNA 和蛋白质组成的微小细胞器。负责蛋白质的合成。在真核细胞中，核糖体可以游离在细胞质中，或附着在粗面内质网上（尽管内质网在 GCSE 阶段不要求）。

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3. Plant Cells and Additional Organelles | 植物细胞及额外细胞器

Plant cells share all the organelles found in animal cells, but they also possess three additional structures that are essential for plant life. You must be able to identify these in diagrams and explain their functions.

植物细胞拥有动物细胞中的所有细胞器，但它们还有三种对植物生命至关重要的额外结构。你必须能够在图中识别它们，并解释其功能。

Cell wall: A rigid layer made of cellulose that surrounds the cell membrane. It provides structural support, gives the cell a fixed shape, and prevents bursting when water enters by osmosis.

细胞壁： 由纤维素组成的坚硬外层，包围着细胞膜。它提供结构支撑，赋予细胞固定形状，并防止细胞因渗透吸水而破裂。

Permanent vacuole: A large, fluid-filled sac bounded by a membrane called the tonoplast. It contains cell sap — a solution of salts, sugars and pigments — and helps maintain turgor pressure, keeping the plant upright.

永久液泡： 一个由液泡膜包围的、充满液体的大囊。内含细胞液——盐、糖和色素的溶液，有助于维持膨压，使植物保持挺立。

Chloroplasts: Oval organelles containing the green pigment chlorophyll. They are the site of photosynthesis, where light energy is converted into chemical energy stored in glucose. Chloroplasts have a double membrane and internal stacks of thylakoids.

叶绿体： 含有绿色色素叶绿素的椭圆形细胞器。它们是光合作用的场所，光能被转化为储存在葡萄糖中的化学能。叶绿体具有双层膜和内部的类囊体堆叠。

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4. Prokaryotic Cells (Bacteria) | 原核细胞（细菌）

Prokaryotic cells are much smaller and simpler than eukaryotic cells. Bacteria are the most common examples. Rather than a true nucleus, the genetic material is a single circular strand of DNA that floats freely in the cytoplasm. Plasmids are small extra rings of DNA that can carry additional genes. Prokaryotes lack membrane-bound organelles such as mitochondria and chloroplasts; their cell wall is made of peptidoglycan, not cellulose or chitin. Some bacteria also have a flagellum for movement and a slime capsule for protection. Ribosomes in bacteria are smaller (70S) than those in eukaryotes.

原核细胞比真核细胞小得多，也简单得多。最常见的例子是细菌。原核细胞没有真正的细胞核，遗传物质是一条游离在细胞质中的单一环状 DNA。质粒是额外的小型 DNA 环，可携带附加基因。原核细胞缺乏膜包被的细胞器，如线粒体和叶绿体；它们的细胞壁由肽聚糖构成，而不是纤维素或几丁质。某些细菌还具有用于运动的鞭毛和用于保护的黏液荚膜。细菌中的核糖体（70S）比真核细胞中的小。

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5. Fungal Cells | 真菌细胞

Fungal cells, such as those of yeast and mushroom hyphae, are eukaryotic but have some features that differ from plant and animal cells. The cell wall is made of chitin, not cellulose. They possess a true nucleus and membrane-bound organelles, including mitochondria and ribosomes. Fungal cells never contain chloroplasts, so they cannot photosynthesise. Instead, they obtain nutrients by absorption. Some fungi, like yeast, are unicellular and have a large vacuole. In multicellular fungi, cells may form thread-like hyphae that can be multinucleate (contain many nuclei).

真菌细胞（如酵母菌和蘑菇菌丝中的细胞）是真核细胞，但具有一些区别于植物细胞和动物细胞的特征。其细胞壁由几丁质构成，而非纤维素。它们拥有真正的细胞核和膜包被的细胞器，包括线粒体和核糖体。真菌细胞从不含有叶绿体，因此不能进行光合作用；它们通过吸收获取营养。有些真菌（如酵母菌）是单细胞的，并有一个大液泡。在多细胞真菌中，细胞可形成丝状的菌丝，这些菌丝可能是多核的（含有多个细胞核）。

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6. Cell Structure Comparison Table | 细胞结构比较表

The following table summarises the presence or absence of key structures in animal, plant, bacterial and fungal cells. Use it as a quick reference when answering compare-and-contrast questions.

下表总结了动物细胞、植物细胞、细菌细胞和真菌细胞中关键结构的存在情况。将其用作回答比较类问题时的快速参考。

Structure	Animal Cell	Plant Cell	Bacterial Cell	Fungal Cell
Cell membrane	Yes	Yes	Yes	Yes
Nucleus	Yes	Yes	No (DNA free in cytoplasm)	Yes
Cytoplasm	Yes	Yes	Yes	Yes
Ribosomes	Yes	Yes	Yes (70S)	Yes
Mitochondria	Yes	Yes	No	Yes
Chloroplasts	No	Yes	No	No
Cell wall	No	Yes (cellulose)	Yes (peptidoglycan)	Yes (chitin)
Large permanent vacuole	No	Yes	No	Sometimes (small)
Plasmids	No	No	Yes	No

Remember: the key differences are that bacterial cells lack a nucleus and membrane-bound organelles, plant cells have cellulose cell walls and chloroplasts, and fungal cell walls contain chitin. Only plant cells have a large permanent vacuole and chloroplasts.

记住：关键区别在于细菌细胞没有细胞核和膜包被的细胞器；植物细胞有纤维素细胞壁和叶绿体；真菌细胞壁含有几丁质。只有植物细胞具有大型永久液泡和叶绿体。

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7. Microscopy and Magnification | 显微镜与放大率

At GCSE level, you must be familiar with light microscopes and the magnification formula. Light microscopes use lenses to magnify specimens, typically up to about ×1500, while electron microscopes have much higher magnifications and resolution. However, the WJEC specification focuses mainly on light microscopy and calculations. The equation you need to know is:

在 GCSE 阶段，你必须熟悉光学显微镜和放大倍数公式。光学显微镜使用透镜放大标本，通常可放大至约 1500 倍，而电子显微镜有更高的放大倍数和分辨率。不过，WJEC 考纲主要关注光学显微镜及其计算。你需要掌握的公式是：

Magnification = Image size / Actual size

This equation can be rearranged to find any one of the three variables if the other two are known. Always ensure that the image size and actual size are in the same units before doing the calculation. Common units include millimetres (mm), micrometres (µm), and nanometres (nm). 1 mm = 1000 µm; 1 µm = 1000 nm.

该公式可以变形，以便在已知其中两个变量的情况下求出第三个。计算前务必确保图像尺寸和实际尺寸使用相同的单位。常见单位包括毫米（mm）、微米（µm）和纳米（nm）。1 mm = 1000 µm；1 µm = 1000 nm。

Example: A student measures the length of a cell image to be 50 mm. The actual cell length is 0.1 mm. Calculate the magnification.

示例： 一名学生测得一个细胞图像的长度为 50 mm，而细胞的实际长度为 0.1 mm。请计算放大倍数。

Magnification = 50 ÷ 0.1 = 500×. If the actual size were given as 25 µm and the image size as 10 mm, you must first convert 10 mm to 10 000 µm, so Magnification =

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