Edexcel Biology 2.1 Cell Structure | 爱德思生物 2.1 细胞结构

📚 Edexcel Biology 2.1 Cell Structure | 爱德思生物 2.1 细胞结构

The Edexcel Biology Unit 2.1 focuses on cell structure, the foundation of all living organisms. Understanding the similarities and differences between animal, plant and bacterial cells is essential for both paper-based and practical examination questions.

爱德思生物第 2.1 单元重点讲解细胞结构，这是所有生物体的基础。掌握动物细胞、植物细胞和细菌细胞之间的异同，对于笔试和实验题都至关重要。

1. Cell Theory | 细胞学说

All living organisms are composed of one or more cells. The cell is the smallest unit that can carry out all life processes, including respiration, growth, reproduction and response to stimuli.

所有生物体由一个或多个细胞组成。细胞是能够进行所有生命过程的最小单位，包括呼吸、生长、繁殖和对刺激的反应。

The modern cell theory states that cells arise only from existing cells by division, and that all cells contain genetic material which is passed on during cell division.

现代细胞学说指出，细胞只能通过分裂从已有细胞产生，所有细胞都含有在细胞分裂时传递的遗传物质。

2. Eukaryotic and Prokaryotic Cells | 真核细胞与原核细胞

Cells can be divided into two main groups: eukaryotic cells, which have a true nucleus enclosed by a nuclear membrane, and prokaryotic cells, which lack a true nucleus.

细胞可分为两大类：真核细胞具有由核膜包被的真正细胞核，而原核细胞没有真正的细胞核。

Animal and plant cells are eukaryotic, while bacterial cells are prokaryotic. Eukaryotic cells are usually larger and contain membrane-bound organelles such as mitochondria and chloroplasts.

动物细胞和植物细胞属于真核细胞，细菌细胞属于原核细胞。真核细胞通常更大，并含有线粒体、叶绿体等有膜细胞器。

3. Animal Cell Organelles | 动物细胞器

A typical animal cell contains the following organelles: cell membrane, cytoplasm, nucleus, mitochondria and ribosomes. The cell membrane controls what enters and leaves the cell.

典型的动物细胞含有以下细胞器：细胞膜、细胞质、细胞核、线粒体和核糖体。细胞膜控制物质的进出。

The nucleus contains the genetic material DNA and controls cell activities. Mitochondria are the site of aerobic respiration, releasing energy for the cell.

细胞核含有遗传物质 DNA，并控制细胞活动。线粒体是有氧呼吸的场所，为细胞释放能量。

• Cell membrane: selectively permeable barrier
  细胞膜：选择透过性屏障
• Cytoplasm: site of many chemical reactions
  细胞质：许多化学反应的场所
• Nucleus: stores genetic information
  细胞核：储存遗传信息

4. Plant Cell Organelles | 植物细胞器

Plant cells contain all the organelles found in animal cells, plus three additional structures: a cell wall, chloroplasts and a permanent vacuole.

植物细胞含有动物细胞中的所有细胞器，另外还有三种结构：细胞壁、叶绿体和中央液泡。

The cell wall is made of cellulose and provides strength and support. Chloroplasts absorb light energy for photosynthesis, and the permanent vacuole stores cell sap and helps maintain turgor pressure.

细胞壁由纤维素组成，提供强度和支持。叶绿体吸收光能进行光合作用，中央液泡储存细胞液并帮助维持膨压。

• Cell wall: made of cellulose, fully permeable
  细胞壁：由纤维素组成，完全透性
• Chloroplasts: contain chlorophyll, site of photosynthesis
  叶绿体：含有叶绿素，光合作用场所
• Permanent vacuole: stores cell sap, supports cell shape
  中央液泡：储存细胞液，维持细胞形状

5. Bacterial Cell Structure | 细菌细胞结构

Bacterial cells are much smaller than plant and animal cells. They are prokaryotic and have no nucleus; instead, their genetic material forms a single circular strand of DNA in the cytoplasm.

细菌细胞比植物和动物

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