📚 IB & OCR Biology: End-of-Term Revision Checklist | IB与OCR生物：期末复习提纲
As the end of term approaches, a structured revision checklist is essential for mastering the core concepts in both IB Biology and OCR A-level Biology. This article provides a comprehensive bilingual overview, highlighting key topics, definitions, and mechanisms that appear frequently in exams. Whether you are preparing for the IB higher level (HL) or the OCR Biology A specification, this guide will help you focus your revision efficiently.
随着学期末临近，一份系统的复习提纲对于掌握IB生物和OCR A-level生物的核心概念至关重要。本文提供一份全面的中英双语概览，突出考试中常见的关键主题、定义和机制。无论你是在准备IB高等级（HL）还是OCR生物A课程，本指南都将帮助你高效地聚焦复习。
Work through the twelve sections below in order, and tick off a syllabus point only when you can explain it out loud without your notes. Anything you cannot explain within one minute becomes the first item of your next revision session.
请按顺序完成以下十二个小节，只有当你能够不看书、口头讲清某个考纲条目时，才在它旁边打勾。任何一分钟内讲不清的内容，就是你下一次复习的首要任务。
1. Cell Biology: Cell Theory and Cell Structure | 细胞生物学：细胞学说与细胞结构
Cell theory states that all living organisms are composed of cells, the cell is the basic unit of life, and all cells arise from pre-existing cells. Exam questions rarely ask you to recite these three statements; they ask you to apply them to an unfamiliar organism or to an unusual observation.
细胞学说指出所有生物体都由细胞组成，细胞是生命的基本单位，并且所有细胞都来自已有的细胞。考试很少要求你背诵这三句话，而是要求你把它应用到陌生生物体或不寻常的观察结果上。
Prokaryotic cells lack a membrane-bound nucleus and membrane-bound organelles, while eukaryotic cells possess compartmentalised structures such as the nucleus, mitochondria, and endoplasmic reticulum. Ribosomes are the only non-membrane-bound structure shared by both cell types, although prokaryotic ribosomes are 70S and eukaryotic cytoplasmic ribosomes are 80S.
原核细胞缺乏膜包裹的细胞核和膜性细胞器，而真核细胞拥有区室化的结构，例如细胞核、线粒体和内质网。核糖体是两类细胞共有的唯一非膜性结构，不过原核核糖体为 70S，真核细胞质核糖体为 80S。
You should also be able to link every organelle to its function: mitochondria for aerobic respiration and ATP synthesis, chloroplasts for photosynthesis, rough endoplasmic reticulum and Golgi apparatus for protein processing and packaging, lysosomes for hydrolysis of macromolecules, and the cytoskeleton for cell shape and movement.
你还应能把每个细胞器与其功能对应起来：线粒体负责有氧呼吸与 ATP 合成，叶绿体负责光合作用，粗面内质网和高尔基体负责蛋白质的加工与包装，溶酶体负责大分子的水解，细胞骨架则维持细胞形状并参与运动。
| Feature | Prokaryotic cell | Eukaryotic cell |
| Nucleus | Absent; circular DNA free in cytoplasm | Present; linear DNA with histones |
| Membrane-bound organelles | Absent | Present (mitochondria, ER, Golgi) |
| Ribosomes | 70S | 80S in cytoplasm |
| Cell wall | Peptidoglycan (bacteria) | Cellulose (plants), chitin (fungi) |
| Typical diameter | 1-5 μm | 10-100 μm |
Remember the magnification and resolution distinction: magnification enlarges the image, whereas resolution is the minimum distance at which two points can still be seen as separate, which is why electron microscopes reveal organelles that light microscopes cannot.
请记住放大率与分辨率的区别：放大率只是把图像放大，而分辨率是两点仍能被分辨开的最小距离，这正是电子显微镜能看到光镜无法显示的细胞器结构的原因。
2. Cell Membranes and Transport | 细胞膜与物质运输
The fluid mosaic model describes the cell membrane as a phospholipid bilayer with embedded proteins, glycoproteins, and cholesterol (in animal cells). The hydrophobic fatty acid tails face inwards, the hydrophilic phosphate heads face outwards, and the whole structure is dynamic rather than rigid.
流动镶嵌模型将细胞膜描述为磷脂双分子层，其中嵌有蛋白质、糖蛋白和胆固醇（在动物细胞中）。疏水的脂肪酸尾部朝向内侧，亲水的磷酸头部朝向外侧，整个结构是动态的而非刚性的。
Membrane transport includes passive processes (diffusion, facilitated diffusion, osmosis) and active transport requiring ATP. Bulk transport occurs via endocytosis and exocytosis, which move material in vesicles and therefore do not require the substance to cross the bilayer directly.
膜运输包括被动过程（扩散、协助扩散、渗透）和需要 ATP 的主动运输。批量运输通过内吞和外排完成，它们以囊泡搬运物质，因此物质本身不必直接穿过双分子层。
| Process | Direction | ATP? | Example |
| Simple diffusion | Down gradient | No | O₂, CO₂ across alveoli |
| Facilitated diffusion | Down gradient | No | Glucose via carrier proteins |
| Osmosis | Down water potential gradient | No | Water through aquaporins |
| Active transport | Against gradient | Yes | Na⁺/K⁺ pump: 3 Na⁺ out, 2 K⁺ in |
Water potential is a useful quantitative idea for both specifications. Pure water has a water potential of 0 kPa, and solutes always lower it, so water moves from the solution with the higher (less negative) water potential to the lower one.
水势对两个课程都是一个有用的定量概念。纯水的水势为 0 kPa，溶质总会使其降低，因此水总是从水势较高（负值较小）的溶液流向水势较低的溶液。
Ψ = Ψs + Ψp
In this equation Ψ is water potential, Ψs is solute potential (always negative in a solution) and Ψp is pressure potential, which becomes positive in a turgid plant cell.
该式中 Ψ 为水势，Ψs 为溶质势（在溶液中总是负值），Ψp 为压力势，在膨压饱满的植物细胞中为正值。
3. Biological Molecules | 生物分子
Water is the solvent of life because it is polar, forms hydrogen bonds, has a high specific heat capacity, a high latent heat of vaporisation, and strong cohesion between molecules. These properties explain its role in transport, temperature buffering, and support in plants.
水是生命的溶剂，因为它具有极性、能形成氢键、比热容高、汽化潜热高，并且分子间有很强的内聚力。这些性质解释了水在运输、温度缓冲以及植物支持方面的作用。
All biological macromolecules are built by condensation reactions and broken down by hydrolysis
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