IB Biology: Cell Structure – Key Concepts and Tips | IB 生物：细胞结构考点精讲

📚 IB Biology: Cell Structure – Key Concepts and Tips | IB 生物：细胞结构考点精讲

Understanding cell structure is fundamental to IB Biology. This revision guide covers the essential concepts: from cell theory and the ultrastructure of prokaryotic and eukaryotic cells to membrane structure, organelles, and the techniques used to study cells. Each section provides key points in both English and Chinese to support bilingual learning and exam success.

理解细胞结构是IB生物学的基础。本复习指南涵盖了基本概念：从细胞学说、原核与真核细胞的超微结构，到膜结构、细胞器以及研究细胞的技术。每个部分都提供中英双语要点，以支持双语学习和考试成功。

1. Cell Theory and Common Features | 细胞学说与共同特征

The cell theory has three main principles: (1) all living things are composed of one or more cells, (2) the cell is the basic structural and functional unit of life, and (3) all cells arise from pre-existing cells by division. However, some organisms challenge these generalizations—for example, striated muscle cells are multinucleated, aseptate fungal hyphae have many nuclei in a continuous cytoplasm, and giant algae like Acetabularia can be single-celled but very large.

细胞学说有三个主要原则：（1）所有生物体都由一个或多个细胞组成，（2）细胞是生命的基本结构和功能单位，（3）所有细胞都来自已存在的细胞通过分裂产生。然而，有些生物对上述概括提出了挑战——例如，横纹肌细胞是多核的，无隔真菌菌丝的连续细胞质中有许多细胞核，而像伞藻这样的大型藻类可以是单细胞的但体型很大。

Despite this diversity, all cells share common features: a plasma membrane that separates the cell from its environment, cytoplasm containing cytosol and organelles, DNA as the heritable material, and ribosomes that synthesize proteins.

尽管存在这些多样性，所有细胞都具有共同特征：将细胞与外界环境分隔开的细胞膜、包含细胞液和细胞器的细胞质、作为遗传物质的DNA以及合成蛋白质的核糖体。

2. Prokaryotic vs Eukaryotic Cells | 原核与真核细胞的比较

Prokaryotic cells (e.g., bacteria and archaea) are structurally simpler than eukaryotic cells. The table below summarises key differences:

原核细胞（如细菌和古菌）在结构上比真核细胞简单。下表总结了关键差异：

Prokaryotes divide by binary fission, while eukaryotes undergo mitosis and meiosis. Both types can have flagella, but the structure differs (prokaryotic flagella are simpler, lacking a 9+2 arrangement).

原核生物通过二分裂繁殖，真核生物进行有丝分裂和减数分裂。两种类型都可以有鞭毛，但结构不同（原核鞭毛更简单，没有9+2微管排列）。

3. Ultrastructure of Eukaryotic Cells: Organelles | 真核细胞的超微结构：细胞器

Eukaryotic cells possess an elaborate system of internal membranes that create distinct compartments. The major organelles include the nucleus, endoplasmic reticulum (ER), Golgi apparatus, mitochondria, chloroplasts (in plants), lysosomes, vacuoles, and peroxisomes. Ribosomes, although not membrane-bound, are essential organelles for protein synthesis. The cytoskeleton provides structural support and facilitates movement.

真核细胞拥有一套复杂的内膜系统，形成不同的区室。主要的细胞器包括细胞核、内质网（ER）、高尔基器、线粒体、叶绿体（存在于植物中）、溶酶体、液泡和过氧化物酶体。核糖体虽然无膜包被，但却是蛋白质合成的重要细胞器。细胞骨架提供结构支持并促进运动。

Each organelle has a specific structure adapted to its function. Compartmentalization allows incompatible chemical reactions to occur simultaneously, increases efficiency, and maintains optimal conditions for enzymatic activity.

每种细胞器都具有适应其功能的特定结构。区室化使得不相容的化学反应能够同时进行，提高了效率，并维持酶活性的最适条件。

4. Nucleus and Ribosomes | 细胞核与核糖体

The nucleus is surrounded by a double membrane called the nuclear envelope, which contains nuclear pores for transport of molecules such as mRNA and proteins. Inside, chromatin (DNA + histones) is present, and the nucleolus is the site of ribosomal RNA (rRNA) synthesis and ribosome assembly.

细胞核由称为核被膜的双层膜包围，核被膜上有核孔，用于mRNA和蛋白质等分子的运输。内部有染色质（DNA + 组蛋白），核仁是核糖体RNA（rRNA）合成和核糖体组装的地方。

Ribosomes are composed of rRNA and proteins, consisting of a large and a small subunit. In eukaryotes, 80S ribosomes are found free in the cytoplasm or bound to the rough ER. They are the sites of translation, where mRNA is decoded into a polypeptide chain.Published by TutorHao | IB Biology Revision Series | aleveler.com

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