Plant and Animal Cells | 植物与动物细胞

📚 Plant and Animal Cells | 植物与动物细胞

Cells are the basic units of life. This article explains the structure of plant and animal cells, the functions of their main organelles, how to observe them with a microscope, and how they are adapted for different jobs. You will also learn how to compare the two cell types clearly for KS3 CIE Biology.

细胞是生命的基本单位。本文介绍植物细胞和动物细胞的结构、主要细胞器的功能、如何用显微镜观察细胞，以及细胞如何适应不同的功能。你还将学会如何清晰地比较这两种细胞类型，为 KS3 CIE 生物课程做好准备。

1. What Are Cells? | 细胞是什么

Cells are the basic structural and functional units of all living organisms. Most individual cells are too small to be seen with the naked eye, so a light microscope is usually needed. Some organisms, such as bacteria and yeast, are unicellular, meaning they consist of only one cell. Plants and animals are multicellular: their bodies are made up of many cells working together. Both plant and animal cells are eukaryotic cells, which means they contain a true nucleus enclosed by a membrane. Understanding cell structure helps explain how living things grow, reproduce, and carry out life processes.

细胞是所有生物体结构和功能的基本单位。大多数单个细胞太小，肉眼无法看到，因此通常需要使用光学显微镜。有些生物，如细菌和酵母，是单细胞生物，也就是说它们只由一个细胞构成。植物和动物是多细胞生物：它们的身体由许多细胞共同组成。植物细胞和动物细胞都属于真核细胞，即它们含有由膜包裹的真正的细胞核。了解细胞结构有助于解释生物如何生长、繁殖以及进行生命活动。

2. Using a Microscope to See Cells | 用显微镜观察细胞

A light microscope magnifies cells using two sets of lenses: the eyepiece lens and the objective lens. The main parts include the eyepiece lens, objective lenses, stage, clips, mirror or lamp, and focusing knobs. Total magnification is calculated by multiplying the eyepiece magnification by the objective lens magnification.

光学显微镜通过两组透镜放大细胞：目镜和物镜。主要部件包括目镜、物镜、载物台、玻片夹、反光镜或灯以及调焦旋钮。总放大倍数通过目镜放大倍数乘以物镜放大倍数来计算。

Total magnification = eyepiece magnification × objective lens magnification

总放大倍数 = 目镜放大倍数 × 物镜放大倍数

To prepare onion epidermis cells, peel a thin layer from inside an onion, place it flat on a slide in a drop of water, add iodine solution, and lower a coverslip. To prepare human cheek cells, gently scrape the inside of the cheek with a cotton bud, smear the sample onto a slide, add methylene blue stain, and cover with a coverslip.

制作洋葱表皮细胞装片时，从洋葱内侧撕下一薄层，平放在载玻片的水滴中，滴加碘液，然后盖上盖玻片。制作人体口腔上皮细胞装片时，用棉签轻轻刮取口腔内壁，将样本涂在载玻片上，滴加亚甲蓝染液，再盖上盖玻片。

3. Animal Cell Structure | 动物细胞结构

A typical animal cell, such as a human cheek cell, contains a cell membrane, cytoplasm, nucleus, and mitochondria. The cell membrane is the outer boundary that controls what enters and leaves the cell. Cytoplasm is a jelly-like fluid where many chemical reactions happen. The nucleus is usually a round structure located near the centre. Mitochondria are small oval organelles that release energy through aerobic respiration. Animal cells do not have a cell wall, chloroplasts, or a large permanent vacuole, which makes their shape quite flexible.

典型的动物细胞，比如人的口腔上皮细胞，含有细胞膜、细胞质、细胞核和线粒体。细胞膜是控制物质进出细胞的外部边界。细胞质是一种胶状液体，许多化学反应在这里发生。细胞核通常是位于中央附近的圆形结构。线粒体是小型椭圆形细胞器，通过有氧呼吸释放能量。动物细胞没有细胞壁、叶绿体和大型液泡，因此形状较为灵活。

4. Plant Cell Structure | 植物细胞结构

A typical plant cell, such as a palisade cell or onion epidermal cell, has all the structures found in animal cells plus three extra features: a cellulose cell wall, a large permanent vacuole, and chloroplasts. The cell wall surrounds the cell membrane and gives the cell a fixed shape. The large permanent vacuole contains cell sap and helps keep the cell firm. Chloroplasts are green organelles that contain chlorophyll and carry out photosynthesis. Not all plant cells contain chloroplasts: root cells and onion epidermal cells usually do not, because they are not exposed to light.

典型的植物细胞，如栅栏细胞或洋葱表皮细胞，具有动物细胞中的所有结构，此外还有三种额外特征：纤维素细胞壁、大型液泡和叶绿体。细胞壁包围细胞膜，使细胞具有固定形状。大型液泡含有细胞液，帮助细胞保持坚挺。叶绿体是含有叶绿素的绿色细胞器，进行光合作用。并非所有植物细胞都含叶绿体：根细胞和洋葱表皮细胞通常没有，因为它们不接触光。

5. The Nucleus: Control Centre | 细胞核：控制中心

The nucleus controls all cell activities, including growth, repair, and reproduction. It contains chromosomes made of DNA. Chromosomes carry genes that determine inherited characteristics such as eye colour or leaf shape. The nucleus is surrounded by a nuclear membrane that separates it from the cytoplasm. In both plant and animal cells, the nucleus is essential because without it the cell cannot divide or function properly. During cell division, the chromosomes are copied so genetic information can be passed to new cells.

细胞核控制所有细胞活动，包括生长、修复和繁殖。它含有由DNA组成的染色体。染色体携带决定遗传特征的基因，例如眼睛颜色或叶片形状。细胞核由核膜包围，将它与细胞质分开。在植物和动物细胞中，细胞核都至关重要，因为没有它，细胞就无法分裂或正常运作。在细胞分裂期间，染色体会被复制，这样遗传信息就可以传递给新细胞。

6. Cytoplasm and Cell Membrane | 细胞质与细胞膜

Cytoplasm is a jelly-like substance that fills the cell and holds organelles in place. Many metabolic reactions, such as the early stages of respiration, occur in the cytoplasm. It contains dissolved nutrients, enzymes, and salts. The cell membrane is selectively permeable, meaning it

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