Cell Structure and Function | 细胞结构与功能

📚 Cell Structure and Function | 细胞结构与功能

In IGCSE Biology, understanding the structure and function of cells is fundamental to every other topic. This article provides a concise yet complete revision guide, aligned with the Edexcel specification, covering animal, plant, and bacterial cells, as well as specialised cells and key laboratory techniques.

在 IGCSE 生物课程中，理解细胞的结构与功能是所有其他主题的基础。本文依据 Edexcel 考纲提供简洁而完整的复习指南，涵盖动物细胞、植物细胞、细菌细胞，以及特化细胞和关键实验技术。

1. The Cell as the Unit of Life | 细胞是生命的基本单位

All living organisms are composed of cells. The cell is the smallest structural and functional unit that can carry out all the processes of life. Organisms may be unicellular (e.g. Amoeba) or multicellular (e.g. humans).

所有生物体都由细胞构成。细胞是能够完成生命活动的最小结构和功能单位。生物可以是单细胞的（如变形虫）或多细胞的（如人类）。

According to cell theory, all new cells are produced by the division of existing cells. In IGCSE Biology, you need to be able to identify and describe the structure of animal and plant cells using light microscope images and diagrams.

根据细胞学说，所有新细胞都是由现有细胞分裂产生的。在 IGCSE 生物中，你需要能够通过光学显微镜图像和示意图识别并描述动物细胞和植物细胞的结构。

2. Animal Cell Structure | 动物细胞的结构

A typical animal cell contains the following structures: a plasma membrane, cytoplasm, a nucleus, mitochondria, and ribosomes. You should know each structure’s function in detail.

典型的动物细胞包含以下结构：质膜、细胞质、细胞核、线粒体和核糖体。你应该详细了解每个结构的功能。

Plasma membrane – controls the movement of substances into and out of the cell; it is partially permeable.
Cytoplasm – a jelly-like fluid where many metabolic reactions occur; holds organelles in place.
Nucleus – contains DNA arranged as chromosomes; controls the cell’s activities and is the site of transcription.
Mitochondria – the site of aerobic respiration, which releases energy (ATP) for the cell.
Ribosomes – the site of protein synthesis, often found on the rough endoplasmic reticulum (not always shown at IGCSE).

3. Plant Cell Structure | 植物细胞的结构

Plant cells have all the structures found in animal cells, plus three additional structures: a cell wall, a permanent vacuole, and (in most photosynthetic cells) chloroplasts.

植物细胞具有动物细胞中的所有结构，另外还包含三种额外结构：细胞壁、永久液泡以及（在大多数光合作用细胞中的）叶绿体。

Cell wall – made of cellulose; provides structural support and prevents bursting under turgor pressure.
Permanent vacuole – filled with cell sap; maintains turgidity and supports the plant.
Chloroplasts – contain chlorophyll; the site of photosynthesis.

The table below summarises the main differences between animal and plant cells.

下表总结了动物细胞与植物细胞的主要区别。

Feature	Animal cell	Plant cell
Cell wall	Absent	Present (cellulose)
Chloroplasts	Absent	Present (in most)
Vacuole	Small/absent	Large permanent vacuole
Stores starch?	Usually stores glycogen	Stores starch

4. Bacterial Cell Structure | 细菌细胞的结构

Bacteria are prokaryotic organisms. Their cells do not have a true nucleus or membrane-bound organelles. You need to know the key features of a bacterial cell.

细菌是原核生物。它们的细胞没有真正的细胞核或膜结合细胞器。你需要了解细菌细胞的关键特征。

Cytoplasm – contains ribosomes (smaller than those in animal/plant cells) and no membrane-bound organelles.
Plasma membrane – controls entry and exit of substances.
Cell wall – made of peptidoglycan (not cellulose), giving shape and protection.
Genetic material – a single circular DNA loop (chromosome) plus small extra pieces called plasmids.
Flagellum (optional) – a tail-like structure used for movement.

Bacteria are much smaller than eukaryotic cells. Under the microscope, their DNA is not enclosed in a nucleus.

细菌比真核细胞小得多。在显微镜下，它们的DNA没有包裹在细胞核中。

5. Specialised Cells | 特化细胞

In multicellular organisms, cells become specialised to perform particular functions. This is called differentiation. You should be able to describe at least a few examples.

在多细胞生物中，细胞会特化以执行特定功能，这一过程称为分化。你应该能够描述至少几个例子。

Red blood cells – biconcave disc shape increases surface area for oxygen loading; they contain haemoglobin and have no nucleus.
Sperm cells – have a tail (flagellum) for swimming, lots of mitochondria for energy, and an acrosome with enzymes to digest the egg membrane.
Root hair cells – have a large surface area due to the hair-like extension, increasing water and mineral uptake.
Palisade mesophyll cells – packed with many chloroplasts to maximise light absorption for photosynthesis.

Each specialised cell is adapted to its function through its shape, size, or organelles.

每个特化细胞都通过其形状、大小或细胞器来适应其功能。

6. Levels of Organisation | 组织的层次

Cells are organised into tissues, organs, and organ systems. For example, muscle cells form muscle tissue; muscle tissue forms the heart (an organ); the heart is part of the circulatory system.

细胞组织成组织、器官和器官系统。例如，肌肉细胞形成肌肉组织；肌肉组织构成心脏（器官）；心脏属于循环系统的一部分。

You should be able to give examples from both plants and animals.

你应该能够举例说明植物和动物中的组织层次。

Animal example: epithelial cell → epithelial tissue → stomach → digestive system
Plant example: leaf palisade cell → palisade tissue → leaf → plant

This hierarchical organisation allows for division of labour and efficiency.

这种层级组织实现了分工与高效。

7. Using a Light Microscope | 使用光学显微镜

The light microscope is a key tool in cell biology. You need to know how to calculate magnification and how to prepare a simple temporary mount.

光学显微镜是细胞生物学的重要工具。你需要知道如何计算放大倍数以及如何制备简单的临时装片。

Common calculations use the equation:

Magnification = Image size ÷ Actual size

Use the triangle method: cover the quantity you want to find. Remember to use the same units before dividing.

使用三角形法：盖住你想求的量。相除前记得换算成相同单位。

Example: If an image is 40 mm and the actual size is 0.02 mm, magnification = 40 ÷ 0.02 = 2000×.

示例：如果图像大小为 40 mm，实际大小为 0.02 mm，则放大倍数 = 40 ÷ 0.02 = 2000×。

8. Drawing Biological Specimens | 绘制生物标本

When drawing cells under the microscope, follow these rules: use a sharp pencil, draw thin clear lines, do not shade, label with straight horizontal lines, and include a scale bar or magnification.

在显微镜下绘制细胞时，请遵循以下规则：用削尖的铅笔，画细而清晰的线条，不要涂阴影，用平直的水平线标注，并包含比例尺或放大倍数。

Your drawing should reflect the relative sizes and shapes of the structures as seen.

你的绘图应反映所见结构的相对大小和形状。

9. Comparing Prokaryotic and Eukaryotic Cells | 比较原核细胞与真核细胞

This is a common exam question. Remember that prokaryotic cells (bacteria) lack a true nucleus and membrane-bound organelles, while eukaryotic cells (animals, plants, fungi) have both.

这是常见的考试题目。请记住，原核细胞（细菌）缺乏真正的细胞核和膜结合细胞器，而真核细胞（动物、植物、真菌）两者都有。

Feature	Prokaryotic	Eukaryotic
Nucleus	Absent	Present
Mitochondria	Absent	Present
Ribosomes	Small	Large
Cell wall material	Peptidoglycan	Cellulose (plants)

10. Common Exam Tips | 常见考试技巧

To maximise your score, always give the precise name of the structure and then its function. Use the same spelling as the specification. For example, write ‘plasma membrane’ not ‘membrane’ alone when referring to the outer boundary.

为了最大化分数，始终给出结构的准确名称及其功能。使用考纲中的拼写。例如，写“质膜”而不是仅写“膜”来表示外边界。

When answering questions about magnification, show your working step by step. If a question says ‘label the structure’, write the label directly on the diagram with a straight line.

回答有关放大倍数的问题时，逐步展示你的计算过程。如果题目要求“标注结构”，请用直线直接在图上写出标注。

11. Quick Revision Checklist | 快速复习清单

Before the exam, make sure you can answer these questions without notes:

考试前，请确保你能不借助笔记回答以下问题：

Can you draw and label an animal cell and a plant cell?
Can you state the function of each organelle?
Can you compare animal, plant, and bacterial cells in a table?
Can you calculate magnification using the equation?
Can you explain how specialised cells are adapted to their functions?

Practise past paper questions on this topic until you can complete them within time limits.

反复练习此主题的历年真题，直到你能够在规定时间内完成。

12. Summary | 总结

Cell structure is the foundation of IGCSE Biology. Master the differences between eukaryotic and prokaryotic cells, know the functions of every structure, and practise drawing and calculations. With this guide, you are ready for the exam.

细胞结构是 IGCSE 生物的基础。掌握真核与原核细胞的区别，了解每个结构的功能，并练习绘图与计算。使用本指南，你已准备好应对考试。

Published by TutorHao | Biology Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）

Cell Structure and Function | 细胞结构与功能