📚 A-Level WJEC Biology: Ultimate Revision Checklist | WJEC A-Level 生物：期末复习提纲
This comprehensive revision checklist covers all the key topics for the WJEC A-Level Biology specification, designed to help you consolidate knowledge and excel in your final exams. From the chemistry of life to complex ecosystems, each section summarises essential concepts, key processes and practical skills. Use it alongside past papers and practical handbooks to target your revision efficiently.
这份全面的复习提纲涵盖了 WJEC A-Level 生物课程的所有关键主题，旨在帮助你巩固知识并在期末考试中取得优异成绩。从生命的化学到复杂的生态系统，每个部分都概括了核心概念、关键过程与实验技能。结合历年真题与实验手册使用，可以更有针对性地高效复习。
1. Biological Molecules | 生物分子
All living organisms share the same fundamental biochemical building blocks: carbohydrates, lipids, proteins and nucleic acids. Monomers are joined by condensation reactions to form polymers, releasing water, while hydrolysis reactions break them apart by adding water. The specific types of bonds – glycosidic, ester, peptide and phosphodiester – determine the structure and function of each macromolecule.
所有生物体都由相同的基本生化构建模块组成：碳水化合物、脂质、蛋白质和核酸。单体通过缩合反应聚合，同时释放水；而水解反应则通过加水将聚合物分解。特定的化学键——糖苷键、酯键、肽键和磷酸二酯键——决定了每种大分子的结构和功能。
Carbohydrates range from monosaccharides (e.g. glucose C₆H₁₂O₆, fructose, ribose) to disaccharides (maltose, sucrose, lactose) and polysaccharides. Starch (α-glucose, 1-4 and 1-6 glycosidic bonds) provides a compact energy store; cellulose (β-glucose, 1-4 bonds, every other monomer inverted) forms strong, insoluble microfibrils for cell walls. Proteins exhibit four levels of structure: primary (sequence of amino acids), secondary (α-helices and β-pleated sheets maintained by hydrogen bonds), tertiary (3D folding driven by hydrophobic interactions, ionic bonds, disulfide bridges and hydrogen bonds) and quaternary (assembly of multiple polypeptides, as in haemoglobin). Lipids include triglycerides (glycerol + three fatty acids via ester bonds) and phospholipids, which spontaneously assemble into a bilayer due to their hydrophilic heads and hydrophobic tails. Nucleic acids DNA and RNA are polymers of nucleotides; DNA stores genetic information as a double helix with complementary base pairing (A-T, C-G), while RNA is usually single-stranded and uses uracil instead of thymine.
碳水化合物的范围从单糖（如葡萄糖 C₆H₁₂O₆、果糖、核糖）到二糖（麦芽糖、蔗糖、乳糖）和多糖。淀粉（α-葡萄糖，1-4 和 1-6 糖苷键）提供了紧凑的能量存储形式；纤维素（β-葡萄糖，1-4 键，每隔一个单体倒置）形成坚固、不溶的微纤丝，构成细胞壁。蛋白质具有四级结构：一级（氨基酸序列），二级（由氢键维持的 α-螺旋和 β-折叠），三级（通过疏水相互作用、离子键、二硫键和氢键驱动的三维折叠）和四级（多条肽链组装，如血红蛋白）。脂质包括甘油三酯（甘油 + 三个脂肪酸，以酯键连接）和磷脂；磷脂因其亲水性头部和疏水性尾部而自发组装成双分子层。核酸 DNA 和 RNA 是核苷酸的聚合物；DNA 以双螺旋形式存储遗传信息，碱基互补配对（A-T，C-G），而 RNA 通常是单链，并用尿嘧啶代替胸腺嘧啶。
Standard biochemical tests are indispensable for identifying these molecules: the Benedict's test for reducing sugars (producing a brick-red precipitate upon heating), the iodine test for starch (blue-black), the biuret test for proteins (violet colour) and the ethanol emulsion test for lipids (milky-white emulsion).
常规生化测试是鉴定这些分子的必备手段：本尼迪克特试剂检测还原糖（加热后产生砖红色沉淀），碘液测试淀粉（蓝黑色），双缩脲试剂检测蛋白质（紫色）以及乙醇乳化法测试脂质（乳白色乳浊液）。
2. Cell Structure & Membranes | 细胞结构与膜
Prokaryotic cells (e.g. bacteria) lack a membrane-bound nucleus and organelles; they possess 70S ribosomes, a single circular chromosome, and often a cell wall of peptidoglycan. Eukaryotic cells contain a true nucleus, 80S ribosomes, and membrane-bound organelles such as mitochondria (site of aerobic respiration), chloroplasts (photosynthesis, containing thylakoid stacks called grana), rough and smooth endoplasmic reticulum, Golgi apparatus, lysosomes, and a large permanent vacuole in plants. The ultrastructure of each organelle is closely linked to its function.
原核细胞（如细菌）缺少有膜包被的细胞核与细胞器；它们拥有 70S 核糖体、一条环形染色体，且细胞壁通常由肽聚糖构成。真核细胞含有真正的细胞核、80S 核糖体以及多种膜包被的细胞器，例如线粒体（有氧呼吸场所）、叶绿体（光合作用，内含称为基粒的类囊体垛叠）、粗面和滑面内质网、高尔基体、溶酶体，以及植物细胞中的中央大液泡。每种细胞器的超微结构都与其功能密切相关。
The fluid mosaic model describes the plasma membrane as a dynamic phospholipid bilayer with embedded proteins, cholesterol (in animal cells) and glycocalyx. Transport across membranes occurs via simple diffusion (passive, small non-polar molecules), facilitated diffusion through channel or carrier proteins (passive, down concentration gradient), active transport (requires ATP, via carrier proteins against gradient), and bulk transport (endocytosis and exocytosis). Water potential ψ is the sum of solute potential ψₛ and pressure potential ψₚ; water moves from higher to lower water potential. In plant cells, turgor pressure is generated when the cell is in a hypotonic solution, whereas animal cells may burst (lysis).
流动镶嵌模型将细胞膜描述为动态的磷脂双分子层，其中嵌有蛋白质、胆固醇（动物细胞）和糖萼。物质跨膜运输包括：简单扩散（被动，小分子非极性物质）、通过通道蛋白或载体蛋白的易化扩散（被动，顺浓度梯度）、主动运输（需 ATP，载体蛋白逆浓度梯度转运）以及批量运输（胞吞和胞吐）。水势 ψ 为溶质势 ψₛ 与压力势 ψₚ 之和；水分从高水势区域向低水势区域移动。在植物细胞中，当处于低渗溶液时产生膨压，而动物细胞则可能破裂（溶血）。
| Transport type | Energy | Proteins | Direction |
|---|---|---|---|
| Simple diffusion | None (passive) | No | Down concentration gradient |
| Facilitated diffusion | None (passive) | Channel/carrier proteins | Down concentration gradient |
| Active transport | ATP required | Carrier proteins | Against concentration gradient |
3. Enzymes & Metabolism | 酶与代谢
specific active site that binds substrate(s). While the lock-and-key model implies a rigid fit, the induced-fit model proposes that the active site changes shape slightly upon substrate binding, stressing bonds and lowering activation energy. Reaction rate depends on temperature (rising until denaturation around 40– erature coefficient Q₁₀ is typically about 2), pH (each enzyme has an optimum), enzyme concentration and substrate concentration. According to the Michaelis– where Vₘₐₓ is the maximum rate when all active sites are occupied, and Kₘ (Michaelis constant) indicates the affinity of the enzyme for the substrate; a low Kₘ means high affinity.
酶是具有特定活性位点的球状蛋白质，能与底物结合。锁钥模型认为活性位点形状固定，而诱导契合模型提出活性位点在底物结合时略微改变构象，拉扯化学键并降低活化能。反应速率受温度（升高直至许多人体酶在 40–50 °C 附近变性；温度系数 Q₁₀ 一般约为 2）、pH（每种酶有最适值）、酶浓度和底物浓度的影响。根据米氏模型，v = Vₘₐₓ[S] / (Kₘ + [S])，其中 Vₘₐₓ 是所有活性位点被占据时的最大速率，Kₘ（米氏常数）反映酶对底物的亲和力；Kₘ 低意味着亲和力高。
Inhibitors reduce enzyme activity. Competitive inhibitors structurally resemble the substrate and bind reversibly to the active site; they increase the apparent Kₘ but do not change Vₘₐₓ because the inhibition can be overcome by excess substrate. Non-competitive inhibitors bind to an allosteric site, altering the enzyme's shape so the active site no longer functions; they lower Vₘₐₓ without affecting Kₘ. End-product inhibition is a form of non-competitive regulation in metabolic pathways. Coenzymes (e.g. NAD⁺, FAD, coenzyme A) and metal ion cofactors are often required for enzyme activity.
抑制剂可降低酶活性。竞争性抑制剂在结构上与底物相似，可逆地与活性位点结合；它们增加表观 Kₘ，但不改变 Vₘₐₓ，因为过量底物可以克服抑制。非竞争性抑制剂结合于别构位点，改变酶的形状使活性位点失活；它们降低 Vₘₐₓ 而不影响 Kₘ。代谢途径中的末端产物抑制是一种非竞争性调控形式。辅酶（如 NAD⁺、FAD、辅酶 A）和金属离子辅因子常常是酶活性所必需的。
| Inhibition type | Kₘ effect | Vₘₐₓ effect |
|---|---|---|
| Competitive | Increases | No change |
| Non-competitive | No change | Decreases |
4. Cell Division & Genetics | 细胞分裂与遗传学
The cell
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