📚 GCSE Biology: Cell Structure – Key Points | GCSE 生物：细胞结构 考点精讲
Cells are the building blocks of all living organisms. In GCSE Biology, understanding cell structure is fundamental, covering the differences between eukaryotic and prokaryotic cells, the organelles found in animal, plant and bacterial cells, and how specialised cells are adapted to their functions. This article summarises the key points you need to know for your exam.
细胞是所有生物体的基本构成单位。在 GCSE 生物中，理解细胞结构是基础，涵盖真核细胞与原核细胞的区别，动物、植物和细菌细胞中含有的细胞器，以及特化细胞如何适应其功能。本文总结了你考试需要掌握的核心考点。
1. The Basics of Cell Theory | 细胞学说的基本概念
All living things are made up of one or more cells. The cell is the simplest unit that can carry out all life processes. New cells are produced from existing cells by cell division.
所有生物都由一个或多个细胞构成。细胞是能够执行所有生命过程的最简单单位。新细胞是通过细胞分裂从已有细胞产生的。
Most cells are microscopic, with animal cells typically ranging from 10 to 30 µm in diameter and plant cells from 10 to 100 µm. The small size of cells means they have a large surface area to volume ratio, which allows efficient exchange of materials with their environment.
大多数细胞是微观的，动物细胞直径通常为 10–30 µm，植物细胞为 10–100 µm。细胞体积小意味着它们具有较大的表面积与体积比，从而能够与环境高效地交换物质。
2. Eukaryotic and Prokaryotic Cells | 真核细胞与原核细胞
Organisms can be grouped based on cell type. Eukaryotic cells have a true nucleus where the genetic material (DNA) is enclosed within a nuclear membrane. Plant and animal cells are eukaryotic.
根据细胞类型，生物可以分为不同类群。真核细胞拥有真正的细胞核，遗传物质（DNA）被核膜包裹。植物和动物细胞是真核细胞。
Prokaryotic cells are much smaller and simpler. They lack a nucleus; instead, their DNA is a single circular chromosome that floats freely in the cytoplasm. Bacteria are prokaryotes. They also may contain small rings of DNA called plasmids.
原核细胞更小、更简单。它们没有细胞核；DNA 是一条环状染色体，游离在细胞质中。细菌是原核生物。它们还可能含有称为质粒的小型环状 DNA。
3. Animal Cell Structure | 动物细胞的结构
A typical animal cell contains the following structures: cell membrane, cytoplasm, nucleus, mitochondria and ribosomes. Under a light microscope, the nucleus and cytoplasm are usually visible, while organelles like mitochondria require higher magnification.
典型的动物细胞含有以下结构：细胞膜、细胞质、细胞核、线粒体和核糖体。在光学显微镜下，通常能看到细胞核和细胞质，而线粒体等细胞器需要更高的放大倍数。
The cell membrane is a thin, partially permeable layer that surrounds the cell and controls the movement of substances in and out. The cytoplasm is a jelly-like substance where most chemical reactions take place.
细胞膜是一层薄薄的、具有选择透过性的膜，包围着细胞并控制物质进出。细胞质是一种凝胶状物质，大部分化学反应在其中进行。
The nucleus contains the cell’s genetic material and controls the cell’s activities. Mitochondria are the sites of aerobic respiration, releasing energy for the cell. Ribosomes are tiny structures where proteins are synthesised.
细胞核含有细胞的遗传物质，并控制细胞的活动。线粒体是有氧呼吸的场所，为细胞释放能量。核糖体是合成蛋白质的微小结构。
4. Functions of Animal Cell Organelles | 动物细胞器的功能
Cell membrane: acts as a barrier and selectively allows substances such as oxygen, water and glucose to pass through, while keeping harmful substances out.
细胞膜：作为屏障，选择性地允许氧气、水和葡萄糖等物质通过，同时阻挡有害物质。
Cytoplasm: a mixture of water and dissolved solutes where enzymes catalyse metabolic reactions, including anaerobic respiration when oxygen is lacking.
细胞质：水和溶解物的混合物，酶在此催化代谢反应，包括在缺氧时进行的无氧呼吸。
Nucleus: stores DNA arranged in chromosomes. The DNA carries the instructions for making proteins and controls cell division and differentiation.
细胞核：储存以染色体形式排列的 DNA。DNA 携带着制造蛋白质的指令，并控制细胞分裂和分化。
Mitochondria: have a folded inner membrane that provides a large surface area for the reactions of aerobic respiration. Cells with high energy demands, such as muscle cells, contain many mitochondria.
线粒体：具有折叠的内膜，为有氧呼吸反应提供较大的表面积。能量需求高的细胞（如肌肉细胞）含有大量线粒体。
Ribosomes: extremely small organelles that can be found free in the cytoplasm or attached to the rough endoplasmic reticulum. They read the genetic code and assemble amino acids into proteins.
核糖体：极小的细胞器，可游离于细胞质中或附着在粗面内质网上。它们读取遗传密码并将氨基酸组装成蛋白质。
5. Plant Cell Structure | 植物细胞的结构
Plant cells contain all the organelles found in animal cells plus three additional structures: a rigid cell wall, a large permanent vacuole, and often chloroplasts. These extra features allow plants to photosynthesise and provide structural support.
植物细胞含有动物细胞中的所有细胞器，还额外具有三种结构：坚硬的细胞壁、一个巨大的永久液泡，通常还有叶绿体。这些额外的特征使植物能够进行光合作用并提供结构支撑。
The cell wall is made of cellulose, which gives the cell its shape and protects it from bursting when water enters by osmosis. The permanent vacuole is filled with cell sap and helps maintain turgor pressure, keeping the plant upright.
细胞壁由纤维素构成，赋予细胞形状，并防止细胞因渗透吸水而破裂。永久液泡充满细胞液，有助于维持膨压，使植物保持挺立。
Chloroplasts contain the green pigment chlorophyll, which captures light energy for photosynthesis. They are mostly found in the palisade mesophyll cells of leaves.
叶绿体含有绿色色素叶绿素，可捕获光能用于光合作用。它们主要存在于叶片的栅栏叶肉细胞中。
6. Functions of Plant Organelles | 植物细胞器的功能
Cell wall: provides strength and support. The cell wall is fully permeable, allowing water and dissolved substances to pass through freely. Adjacent plant cells are often joined by a middle lamella that helps stick them together.
细胞壁：提供强度与支撑。细胞壁是全透性的，水和小分子溶质可自由通过。相邻植物细胞通常由胞间层连接，帮助细胞黏合。
Permanent vacuole: stores water, ions, sugars and sometimes pigments or waste products. When the vacuole is full, the cytoplasm pushes against the cell wall, making the cell turgid and supporting the plant tissue.
永久液泡：储存水分、离子、糖类，有时还有色素或废物。当液泡充满时，细胞质挤压细胞壁，使细胞成为坚挺状态，支撑植物组织。
Chloroplasts: each chloroplast contains stacks of membranes called thylakoids, where the light-dependent reactions of photosynthesis occur. The stroma is the fluid where the light-independent (Calvin cycle) reactions take place.
叶绿体：每个叶绿体含有称为类囊体的膜堆叠，光合作用的光依赖反应在此发生。基质是进行光不依赖反应（卡尔文循环）的液体环境。
7. Bacterial Cell Structure | 细菌细胞的结构
Bacterial cells are prokaryotic and therefore much simpler in structure. They have a cell wall (made of peptidoglycan, not cellulose), a cell membrane and cytoplasm. Instead of a nucleus, the genetic material forms a single, circular strand of DNA that lies in the cytoplasm.
细菌细胞是原核细胞，结构简单得多。它们有细胞壁（由肽聚糖构成，而非纤维素）、细胞膜和细胞质。遗传物质是一条环状 DNA，位于细胞质中，取代了细胞核。
Many bacteria also contain small loops of DNA called plasmids, which can be transferred between cells and often carry genes for antibiotic resistance. Some bacteria have a flagellum (plural flagella), a long whip-like tail that rotates to move the cell.
许多细菌还含有小型环状 DNA 称为质粒，质粒可以在细胞间转移，常携带抗生素抗性基因。有些细菌具有鞭毛，一种长鞭状结构，通过旋转推动细胞运动。
Bacterial cells do not contain mitochondria, chloroplasts or a permanent vacuole. Instead, enzymes for respiration are located on the cell membrane. Ribosomes in bacteria are smaller (70S) than those in eukaryotic cells (80S).
细菌细胞不含线粒体、叶绿体或永久液泡。取而代之的是，呼吸酶位于细胞膜上。细菌的核糖体（70S）比真核细胞中的（80S）更小。
8. Comparison of Cell Types | 细胞类型的比较
Presence of a nucleus: animal and plant cells have a distinct nucleus enclosed by a nuclear membrane, whereas bacterial cells lack a nucleus and their DNA is free in the cytoplasm.
细胞核的存在：动物和植物细胞拥有被核膜包裹的清楚细胞核，而细菌细胞没有细胞核，其 DNA 游离于细胞质中。
Cell wall: animal cells do not possess a cell wall. Plant cells have a cellulose cell wall. Bacterial cells have a cell wall made of different material (peptidoglycan).
细胞壁：动物细胞没有细胞壁。植物细胞具有纤维素细胞壁。细菌细胞的细胞壁由不同物质（肽聚糖）构成。
Chloroplasts and vacuole: chloroplasts are only present in plant cells (and some algae). A large permanent vacuole is characteristic of mature plant cells but is absent in animal and bacterial cells.
叶绿体和液泡：叶绿体仅存在于植物细胞（及某些藻类）中。巨大的永久液泡是成熟植物细胞的特征，动物细胞和细菌细胞中不存在。
Mitochondria: present in all eukaryotic cells (both animal and plant) but absent in bacteria. In bacteria, respiration occurs across the cell membrane.
线粒体：存在于所有真核细胞（动物和植物）中，但细菌中没有。在细菌中，呼吸作用发生在细胞膜上。
DNA organisation: in eukaryotes, DNA is organised into linear chromosomes inside the nucleus. In prokaryotes, it is a single, circular chromosome, often accompanied by plasmids.
DNA 组织方式：在真核生物中，DNA 被组织成细胞核内的线性染色体。在原核生物中，它是一条环状染色体，通常伴有质粒。
9. Specialised Animal Cells | 特化的动物细胞
Sperm cell: adapted for reproduction. It has a streamlined head containing the nucleus and an acrosome with enzymes to penetrate the egg. The midpiece is packed with mitochondria to provide energy for the tail (flagellum) which propels the cell towards the egg.
精子细胞：适应于生殖。它具有流线型的头部，内含细胞核和含有酶的顶体，用于穿透卵子。中段密集排列着线粒体，为尾巴（鞭毛）提供能量，推动细胞游向卵子。
Red blood cell: specialised for oxygen transport. Its biconcave disc shape increases surface area for oxygen uptake. Mature red blood cells lack a nucleus and most organelles, maximising space for the oxygen-carrying protein haemoglobin.
红细胞：特化于氧气运输。其双凹圆盘形状增加了吸收氧气的表面积。成熟红细胞没有细胞核和大多数细胞器，为携氧蛋白血红蛋白腾出最大空间。
Nerve cell (neuron): designed to transmit electrical impulses rapidly. It has a long axon covered by a myelin sheath (formed by Schwann cells in GCSE contexts) that insulates the signal. The branched dendrites make connections with other neurons.
神经细胞（神经元）：适于快速传递电冲动。它具有长轴突，被髓鞘（在 GCSE 范围内由施万细胞形成）包裹以绝缘信号。分支的树突与其他神经元建立连接。
Muscle cell: adapted to contract. Muscle cells are elongated and contain many mitochondria to supply the ATP needed for contraction. They also contain specialised proteins (actin and myosin) that slide past each other to shorten the cell.
肌肉细胞：适应于收缩。肌肉细胞呈细长状，含有大量线粒体，以提供收缩所需的 ATP。它们还含有特殊的蛋白质（肌动蛋白和肌球蛋白），这些蛋白相互滑动使细胞缩短。
10. Specialised Plant Cells | 特化的植物细胞
Root hair cell: found near the tips of roots, it has a long, thin extension that greatly increases the surface area for absorption of water and mineral ions from the soil. The cell contains many mitochondria to provide energy for active transport of ions against the concentration gradient.
根毛细胞：位于根尖附近，具有细长的突起，大大增加了吸收土壤中水分和矿质离子的表面积。该细胞含有许多线粒体，为逆浓度梯度主动运输离子提供能量。
Palisade mesophyll cell: located in the upper part of a leaf, these cells are packed with chloroplasts to capture maximum light for photosynthesis. Their columnar shape and close arrangement help absorb light efficiently.
栅栏叶肉细胞：位于叶片上部，这些细胞内充满了叶绿体，以最大限度地捕获光能进行光合作用。其柱状形态和紧密排列有助于高效吸收光线。
Xylem vessel cell: formed from dead cells that have lost their cytoplasm and end walls, creating a continuous, hollow tube. The cell walls are strengthened with lignin, which makes them waterproof and provides structural support for the plant. Xylem transports water and dissolved minerals upwards from the roots.
木质部导管细胞：由失去细胞质和端壁的死细胞形成，产生连续的空心管道。细胞壁由木质素加强，使其防水并为植物提供结构支撑。木质部将水分和溶解的矿物质从根部向上运输。
Phloem companion cells and sieve tubes: phloem transports sugars and amino acids. Sieve tubes are living cells that lack a nucleus but are supported by companion cells which provide metabolic functions and energy through many mitochondria.
韧皮部伴胞与筛管：韧皮部运输糖类和氨基酸。筛管是活细胞，没有细胞核，但由伴胞支持，伴胞通过许多线粒体提供代谢功能和能量。
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