Cell Structure and Function | 细胞结构与功能

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

Cell biology is the foundation of all IGCSE Biology. Understanding how cells are organised, how they work, and how they are studied is essential for exam success. This revision guide covers the key concepts you need for the Edexcel IGCSE Biology syllabus.

细胞生物学是 IGCSE 生物学的基础。理解细胞如何组织、如何工作以及如何被研究，对于考试成功至关重要。本复习指南涵盖 Edexcel IGCSE 生物学大纲所需的关键概念。

1. Introduction to Cell Theory | 细胞理论简介

The cell theory is a unifying principle in biology. It states that all living organisms are composed of one or more cells; the cell is the basic unit of structure and organisation in organisms; and all cells arise from pre-existing cells.

细胞理论是生物学中的统一原理。它指出所有生物体由一个或多个细胞组成；细胞是生物体结构和组织的基本单位；所有细胞都来自已有的细胞。

This theory was developed in the 19th century by scientists such as Schleiden, Schwann, and Virchow. It remains a key concept in modern biology and underpins all studies of life processes.

该理论由施莱登、施旺和菲尔绍等科学家在 19 世纪发展而来。它至今仍是现代生物学中的关键概念，并支撑着对所有生命过程的研究。

2. Animal and Plant Cells | 动植物细胞

Despite their diversity, all eukaryotic cells share common structures. Animal cells typically contain a nucleus, cytoplasm, cell membrane, mitochondria, and ribosomes. Plant cells also have a cell wall, chloroplasts, and a large permanent vacuole.

尽管种类多样，所有真核细胞都拥有共同的结构。动物细胞通常包含细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞还拥有细胞壁、叶绿体和大而永久的液泡。

Both cell types carry out essential life processes such as respiration, protein synthesis, and waste removal. The differences in structure reflect differences in function and mode of life.

两种细胞都执行基本生命过程，如呼吸、蛋白质合成和废物排出。结构上的差异反映了功能和生活方式的差异。

Animal cells are generally smaller and irregular in shape, as they lack a rigid cell wall.

动物细胞通常较小且形状不规则，因为它们缺少坚硬的细胞壁。
Plant cells have a cellulose cell wall that provides structural support.

植物细胞具有提供结构支持的纤维素细胞壁。
Chloroplasts are present in plant cells to carry out photosynthesis.

叶绿体存在于植物细胞中以进行光合作用。

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

The nucleus contains DNA and controls cell activities. It is surrounded by a nuclear membrane with pores for communication with the cytoplasm.

细胞核含有 DNA 并控制细胞活动。它由带有核孔的核膜包围，以便与细胞质进行交流。

Cytoplasm is the gel-like fluid where organelles are suspended. Many metabolic reactions occur here, including glycolysis.

细胞质是悬浮有细胞器的凝胶状液体。许多代谢反应在这里发生，包括糖酵解。

The cell membrane controls the movement of substances in and out of the cell. It is selectively permeable and plays a role in cell signalling.

细胞膜控制物质进出细胞。它具有选择性通透性，并在细胞信号传导中发挥作用。

Mitochondria are the sites of aerobic respiration, producing ATP for cellular activities. Cells with high energy demands, such as muscle cells, have many mitochondria.

线粒体是有氧呼吸的场所，为细胞活动产生 ATP。能量需求高的细胞（如肌肉细胞）含有大量线粒体。

Ribosomes are small structures that synthesize proteins. They may be free in the cytoplasm or attached to the rough endoplasmic reticulum.

核糖体是合成蛋白质的小结构。它们可游离在细胞质中，或附着在粗糙内质网上。

Plant-specific organelles include chloroplasts (photosynthesis), a permanent vacuole (turgor support), and the cell wall (protection and shape).

植物特有的细胞器包括叶绿体（光合作用）、永久液泡（膨压支持）和细胞壁（保护和形状）。

4. Specialised Cells | 特化细胞

Multicellular organisms have specialised cells that are adapted to perform specific functions. For example, red blood cells contain haemoglobin and have no nucleus to maximise oxygen transport.

多细胞生物具有特化细胞，这些细胞经过适应以执行特定功能。例如，红细胞含有血红蛋白并且没有细胞核，以最大化氧气运输。

Root hair cells increase surface area for water and mineral absorption. They have a large surface area and thin cell walls.

根毛细胞增加表面积以吸收水分和矿物质。它们具有大表面积和薄细胞壁。

Nerve cells are long and branched to transmit electrical impulses quickly. Muscle cells contain many mitochondria to provide energy for contraction.

神经细胞长且具有分支，以快速传递电脉冲。肌肉细胞含有许多线粒体，以为收缩提供能量。

Sperm cells have a tail for movement and enzymes to penetrate the egg. These adaptations illustrate the relationship between structure and function.

精子细胞有尾用于运动，并含有酶以穿透卵细胞。这些适应性说明了结构与功能之间的关系。

5. Cell Organisation | 细胞组织化

In complex organisms, cells are organised into tissues, organs, and organ systems. A tissue is a group of cells with similar structure and function working together.

在复杂生物中，细胞组织成组织、器官和器官系统。组织是一组结构和功能相似并共同工作的细胞。

An organ is made of different tissues that work together to perform a specific function. For example, the stomach contains muscle tissue, epithelial tissue, and glandular tissue.

器官由不同组织组成，这些组织共同执行特定功能。例如，胃包含肌肉组织、上皮组织和腺体组织。

Organ systems are groups of organs that carry out major body functions. The digestive system, respiratory system, and circulatory system are examples.

器官系统是执行主要机体功能的一组器官。消化系统、呼吸系统和循环系统都是例子。

6. Microscopy and Magnification | 显微镜与放大

Microscopes allow us to study cells. Light microscopes use light to magnify objects up to about ×1000, while electron microscopes can magnify up to ×1,000,000 and reveal ultrastructure.

显微镜使我们能够研究细胞。光学显微镜使用光放大物体至约 1000 倍，而电子显微镜可放大至 1,000,000 倍并显示超微结构。

Magnification is calculated using the equation: magnification = size of image ÷ actual size. Units must be converted carefully (1 mm = 1000 μm).

放大倍数通过公式计算：放大倍数 = 图像大小 ÷ 实际大小。单位必须小心换算（1 mm = 1000 μm）。

Magnification = Image size ÷ Actual size
放大倍数 = 图像大小 ÷ 实际大小

To measure real cell sizes, you can use a graticule and a stage micrometer. This skill is commonly tested in practical questions.

要测量实际细胞大小，您可以使用目镜测微尺和载台测微尺。这项技能常在实验题中考查。

7. Prokaryotic vs Eukaryotic Cells | 原核与真核细胞

Eukaryotic cells (plants, animals, fungi, protists) contain a membrane-bound nucleus and membrane-bound organelles. Prokaryotic cells (bacteria) do not have a nucleus or membrane-bound organelles.

真核细胞（植物、动物、真菌、原生生物）含有膜结合的细胞核和膜结合的细胞器。原核细胞（细菌）没有细胞核或膜结合的细胞器。

Bacterial cells have circular DNA known as a plasmid, a capsule, and small ribosomes. They are typically much smaller than eukaryotic cells.

细菌细胞拥有称为质粒的环状 DNA、荚膜和小核糖体。它们通常比真核细胞小得多。

The key differences are tabulated below:

关键区别如下表所示：

Feature (特征)	Eukaryotic cells (真核细胞)	Prokaryotic cells (原核细胞)
Nucleus (细胞核)	Present (有)	Absent (无)
Membrane-bound organelles	Present (有)	Absent (无)
Ribosome size (核糖体大小)	Large (80S)	Small (70S)
DNA arrangement	Linear chromosomes (线性染色体)	Circular plasmid/chromosome (环状质粒/染色体)
Cell wall (if present)	Cellulose (plant) / Chitin (fungi)	Peptidoglycan (肽聚糖)

8. Cell Division (Mitosis) | 细胞分裂（有丝分裂）

Mitosis is the process by which a eukaryotic cell divides to produce two genetically identical daughter cells. It is used for growth, repair, and asexual reproduction.

有丝分裂是真核细胞分裂产生两个遗传上相同的子细胞的过程。它用于生长、修复和无性生殖。

Before mitosis, DNA replicates so that each chromosome consists of two sister chromatids. During mitosis, these chromatids are separated and distributed equally.

在有丝分裂前，DNA 复制，使每条染色体由两条姐妹染色单体组成。在有丝分裂期间，这些染色单体被分开并平均分配。

The stages of mitosis are prophase, metaphase, anaphase, and telophase. After cytokinesis, two identical cells are formed.

有丝分裂的各个阶段是前期、中期、后期和末期。胞质分裂后形成两个相同的细胞。

Mitosis is important for maintaining chromosome number and genetic stability in an organism.

有丝分裂对于维持生物体中的染色体数目和遗传稳定性很重要。

9. Diffusion, Osmosis and Active Transport | 扩散、渗透与主动运输

Substances move across cell membranes by passive and active processes. Diffusion is the net movement of particles from a high to a low concentration, down a concentration gradient.

物质通过被动和主动过程穿过细胞膜。扩散是粒子从高浓度到低浓度（沿浓度梯度向下）的净移动。

Osmosis is the diffusion of water across a selectively permeable membrane. Water moves from a dilute solution (high water potential) to a concentrated solution (low water potential).

渗透是水通过选择性通透膜的扩散。水从稀溶液（高水势）移动到浓溶液（低水势）。

Active transport is the movement of particles against a concentration gradient, from low to high concentration. This requires energy from respiration.

主动运输是粒子逆浓度梯度（从低浓度到高浓度）的移动。这需要呼吸作用产生的能量。

Sodium-potassium pumps and glucose absorption in the ileum are classic examples of active transport in humans.

人体中钠钾泵和回肠中的葡萄糖吸收是主动运输的典型例子。

10. Common Exam Questions and Tips | 常见考试题目与技巧

In exams, you may be asked to label diagrams, compare cell types, or calculate magnification. Always use the correct units and show your working.

考试中，您可能会被要求标注图表、比较细胞类型或计算放大倍数。始终使用正确的单位并展示您的计算过程。

For diagrams, draw neat pencil lines and label with straight lines. Remember that plant cells have a cell wall, chloroplasts, and a vacuole; animal cells do not.

对于图表，用铅笔画出整洁的线条，并用直线标注。记住植物细胞有细胞壁、叶绿体和液泡；动物细胞没有。

When describing osmosis, use the term ‘water potential’ instead of just ‘concentration’. This shows a deeper understanding.

在描述渗透作用时，使用术语’水势’而不仅仅是’浓度’。这显示更深的理解。

Practice past paper questions on cell structure and transport. Time yourself and review mark schemes to learn key phrases.

练习关于细胞结构和运输的历年真题。为自己计时并复习评分标准，学习关键短语。

Understanding the relationship between structure and function is essential for answering application questions that appear at the end of the paper.

理解结构与功能之间的关系对于回答试卷末尾的应用题至关重要。

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Cell Structure and Function | 细胞结构与功能