Cell Biology and Microscopy | 细胞生物学与显微镜技术

📚 Cell Biology and Microscopy | 细胞生物学与显微镜技术

Cell biology underpins much of the Cambridge AS & A Level Biology course. This article reviews the structural organisation of prokaryotic and eukaryotic cells, the functions of key organelles, and the principles and calculations behind light and electron microscopy.

细胞生物学是剑桥 AS 与 A Level 生物课程的重要基础。本文回顾原核细胞与真核细胞的结构组织、关键细胞器的功能，以及光学显微镜和电子显微镜背后的原理与计算。

1. The Cell Theory | 细胞学说

The modern cell theory states that all living organisms are composed of one or more cells, the cell is the basic unit of structure and function, and all cells arise from pre-existing cells by cell division.

现代细胞学说指出，所有生物体都由一个或多个细胞组成，细胞是结构和功能的基本单位，所有细胞都来自已有细胞的分裂。

Exceptions and complications exist. Skeletal muscle fibres are multinucleate, fungal hyphae may be aseptate, and viruses are acellular, so they do not fit the classical cell theory perfectly.

也存在例外和特殊情况。骨骼肌纤维是多核的，真菌菌丝可能无隔，病毒是非细胞结构，因此它们并不完全符合经典细胞学说。

In Cambridge exams, you should be able to discuss evidence for the cell theory and explain why some structures are not typical cells.

在剑桥考试中，你应能讨论细胞学说的证据，并解释为什么某些结构不是典型细胞。

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

Prokaryotic cells, such as bacteria, lack a membrane-bound nucleus and membrane-bound organelles. Their DNA is circular and lies free in the cytoplasm as a nucleoid.

原核细胞（如细菌）没有膜包被的细胞核和膜包被的细胞器。它们的 DNA 是环状的，裸露在细胞质中形成拟核。

They possess 70S ribosomes, a peptidoglycan cell wall, a cell membrane, plasmids, and sometimes a capsule and flagella. Some cyanobacteria have thylakoid membranes for photosynthesis.

它们具有 70S 核糖体、肽聚糖细胞壁、细胞膜、质粒，有时还有荚膜和鞭毛。一些蓝细菌具有用于光合作用的类囊体膜。

Eukaryotic cells have a true nucleus, 80S ribosomes, linear DNA associated with histone proteins, and compartmentalised organelles such as mitochondria, chloroplasts, endoplasmic reticulum and Golgi apparatus.

真核细胞具有真正的细胞核、80S 核糖体、与组蛋白结合的线性 DNA，以及线粒体、叶绿体、内质网和高尔基体等分区化的细胞器。

Comparing the two cell types is a frequent exam task, especially in tables covering size, DNA form, ribosomes and cell wall composition.

比较这两类细胞是常见的考试任务，尤其是在覆盖大小、DNA 形式、核糖体和细胞壁组成的表格题中。

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

The nucleus contains chromatin and the nucleolus; it controls gene expression and manufactures ribosomal RNA.

细胞核含有染色质和核仁；它控制基因表达并合成核糖体 RNA。

Rough endoplasmic reticulum is studded with ribosomes and transports and modifies newly synthesised proteins; smooth ER synthesises lipids and detoxifies chemicals.

粗面内质网附着核糖体，运输和修饰新合成的蛋白质；光面内质网合成脂质并解毒化学物质。

The Golgi apparatus modifies, packages and sorts proteins into vesicles for secretion or delivery to lysosomes.

高尔基体对蛋白质进行修饰、包装和分选，装入囊泡，用于分泌或运送至溶酶体。

• Mitochondrion: carries out aerobic respiration and synthesises ATP.
  线粒体：进行有氧呼吸并合成 ATP。
• Chloroplast: carries out photosynthesis in plant and algal cells.
  叶绿体：在植物和藻类细胞中进行光合作用。
• Lysosome: contains hydrolytic enzymes for intracellular digestion.
  溶酶体：含有用于细胞内消化的水解酶。
• Large permanent vacuole: stores solutes and maintains turgor in plant cells.
  大的永久液泡：在植物细胞中储存溶质并维持膨压。
• Centrioles: organise spindle fibres during cell division in animal cells.
  中心粒：在动物细胞分裂时组织纺锤丝。

4. Plant, Animal and Fungal Cells | 植物、动物与真菌细胞

Plant cells have a cellulose cell wall, a large permanent vacuole, and chloroplasts in photosynthetic tissues;

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