A complete bilingual revision guide covering every key concept for WJEC GCSE Biology Cells.
1. Cell Theory 细胞学说
EN: The cell is the basic structural and functional unit of all life. All cells arise from pre-existing cells through division. Robert Hooke first observed cells in 1665. Schleiden and Schwann later formalised cell theory, establishing that all plants and animals are composed of cells.
中文：细胞是所有生命体的基本结构和功能单位。所有细胞来自已有细胞的分裂。1665年罗伯特·胡克首次观察到细胞，施莱登和施旺随后提出细胞学说，确立动植物均由细胞构成。
2. Microscopy 显微镜技术
EN: Light microscopes use visible light, achieving ×2000 magnification and ~200 nm resolution. Electron microscopes use electron beams, reaching ×2,000,000 with ~0.2 nm resolution. Formula: total magnification = eyepiece × objective lens. Electron microscopes require dead specimens in a vacuum — living cells cannot be observed.
中文：光学显微镜使用可见光，放大×2000，分辨率~200 nm。电子显微镜用电子束，可达×2,000,000，分辨率~0.2 nm。公式：总放大倍率=目镜×物镜。电子显微镜需真空死亡样本，无法观察活细胞。
3. Animal vs Plant Cells 动植物细胞
EN: Shared structures: nucleus, cytoplasm, cell membrane, mitochondria, ribosomes. Plant-only: cell wall (cellulose), permanent vacuole (cell sap), chloroplasts (photosynthesis). The cell wall provides support and prevents osmotic bursting.
中文：共有：细胞核、细胞质、细胞膜、线粒体、核糖体。植物独有：细胞壁（纤维素）、永久液泡（细胞液）、叶绿体（光合作用）。细胞壁提供支撑并防止渗透破裂。
4. Bacterial Cells 细菌细胞
EN: Bacteria are prokaryotes — no true nucleus. They have a single circular chromosome, plasmids (small DNA rings), 70S ribosomes, a cell membrane, and a peptidoglycan cell wall. Some possess a capsule, flagella (movement), or pili (attachment).
中文：细菌是原核生物——无真正细胞核。含单条环状染色体、质粒（DNA小环）、70S核糖体、细胞膜和肽聚糖细胞壁。有些具荚膜、鞭毛（运动）或菌毛（附着）。
5. Organelle Functions 细胞器功能
EN: Nucleus — stores DNA, controls cell. Cytoplasm — site of metabolic reactions. Cell membrane — selectively permeable barrier. Mitochondria — aerobic respiration, produces ATP. Ribosomes — protein synthesis. Chloroplasts — photosynthesis, contains chlorophyll. Cell wall — structural support, fully permeable. Permanent vacuole — stores sap, maintains turgor.
中文：细胞核——储存DNA，控制细胞。细胞质——代谢反应场所。细胞膜——选择性通透屏障。线粒体——有氧呼吸，产生ATP。核糖体——蛋白质合成。叶绿体——光合作用，含叶绿素。细胞壁——结构支撑，完全通透。永久液泡——储存细胞液，维持膨压。
6. Specialised Cells 特化细胞
EN: Sperm — streamlined, acrosome enzymes, many mitochondria, flagellum. Nerve — long axon, myelin sheath, dendrites. Muscle — many mitochondria, contractile fibres. Root hair — long extension for water absorption. Xylem — dead hollow tubes, lignin-reinforced. Phloem — sieve plates, companion cells.
中文：精子——流线型，顶体酶，大量线粒体，鞭毛。神经——长轴突，髓鞘，树突。肌肉——大量线粒体，收缩纤维。根毛——长突起吸水。木质部——死细胞中空管，木质素加固。韧皮部——筛板，伴胞。
7. Mitosis 有丝分裂
EN: Mitosis produces two genetically identical daughter cells. Interphase — DNA replicates. Prophase — chromosomes condense, nuclear membrane breaks. Metaphase — chromosomes align at equator. Anaphase — chromatids separate to poles. Telophase — new nuclear membranes form. Cytokinesis — cytoplasm divides. Used for growth, repair, asexual reproduction.
中文：有丝分裂产生两个遗传相同的子细胞。间期——DNA复制。前期——染色体凝聚，核膜解体。中期——染色体赤道排列。后期——染色单体分离至两极。末期——新核膜形成。胞质分裂——细胞质分裂。用于生长、修复和无性繁殖。
8. Stem Cells 干细胞
EN: Stem cells are undifferentiated and can become specialised cells. Embryonic stem cells are pluripotent — any cell type. Adult stem cells (bone marrow) are multipotent — limited potential. Plant meristems in root/shoot tips enable lifelong growth. WJEC may ask about ethical issues of embryonic stem cell research.
中文：干细胞未分化，可分化为特化细胞。胚胎干细胞多能——可分化为任何类型。成体干细胞（骨髓）多向——潜力有限。植物分生组织位于根尖茎尖，使其终生生长。WJEC可能考查胚胎干细胞研究的伦理问题。
9. Transport 物质运输
EN: Diffusion — particles move from high to low concentration, passive. Osmosis — water diffuses across a partially permeable membrane from high to low water potential. Active transport — moves against gradient using ATP and carrier proteins. Classic WJEC practical: potato cylinders in sugar solutions to study osmosis.
中文：扩散——粒子高浓度→低浓度，被动运输。渗透——水分子通过部分通透膜从高水势→低水势。主动运输——逆梯度移动，需要ATP和载体蛋白。WJEC经典实验：土豆圆柱体在不同糖浓度中探究渗透。
10. Exam Tips 考试技巧
EN: (1) Use straight label lines on diagrams. (2) Correct units: μm for cells, nm for organelles. (3) Use "whereas" and "in contrast" for comparison questions. (4) Six-mark questions — one distinct point per mark. (5) Master the magnification formula: M = image size / actual size; practice mm↔μm↔nm (×1000 each step). (6) Read question stems carefully — WJEC embeds clues in scenarios.
中文：（1）图表用直线标注。（2）正确单位：细胞用μm，细胞器用nm。（3）对比题用"而""相比之下"。（4）六分题每个明确要点一分。（5）掌握放大倍率公式：M=图像尺寸/实际尺寸；练习mm↔μm↔nm换算（每级×1000）。（6）仔细阅读题干——WJEC情景中常嵌线索。
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