📚 A-Level Edexcel Biology: End-of-Term Revision Guide | A-Level Edexcel 生物：期末复习提纲
This end-of-term revision guide brings together the most important topics from the Edexcel A-Level Biology specification. Whether you are preparing for a mock or a final assessment, use this checklist to review key concepts, common exam traps and essential practical skills. Each section is written to help you test your understanding and identify gaps before you walk into the exam hall.
这份期末复习提纲汇总了 Edexcel A-Level 生物学科最核心的主题。无论你是在准备模拟考试还是最终测评，都可以利用这份清单回顾关键概念、常见失分点和必考的实验技能。每个部分旨在帮助你检验理解并找出知识漏洞，让你自信地走进考场。
1. Biological Molecules: Key Concepts | 生物分子：关键概念
All living organisms are built from four major groups of biological molecules: carbohydrates, lipids, proteins and nucleic acids. Learning to recognise the monomer units (monosaccharides, glycerol and fatty acids, amino acids, nucleotides) and the condensation reactions that polymerise them is essential. Be confident drawing ring forms of α‑ and β‑glucose and the glycosidic bond in maltose.
所有生物都由四大类生物分子构成：碳水化合物、脂质、蛋白质和核酸。学会识别单体单元（单糖、甘油和脂肪酸、氨基酸、核苷酸）以及使它们聚合的缩合反应至关重要。要能熟练画出α‑和β‑葡萄糖的环状结构以及麦芽糖中的糖苷键。
Qualitative tests are frequently examined: Benedict’s reagent for reducing sugars (brick‑red precipitate), heating with acid and then Benedict’s for non‑reducing sugars, iodine solution for starch (blue‑black) and the biuret test for proteins (purple). The emulsion test for lipids produces a cloudy white layer.
定性检测是常考内容：本尼迪克特试剂检测还原糖（砖红色沉淀），先加酸加热再用本尼迪克特试剂检测非还原糖，碘液检测淀粉（蓝黑色），双缩脲试剂检测蛋白质（紫色）。脂质的乳浊液测试会形成浑浊的白色层。
Protein structure has four levels: primary (amino acid sequence), secondary (α‑helix and β‑pleated sheet held by hydrogen bonds), tertiary (3D folding stabilised by hydrogen bonds, ionic bonds, disulfide bridges and hydrophobic interactions) and quaternary (more than one polypeptide chain). The specific shape of the active site in enzymes is determined by the tertiary structure.
蛋白质结构有四个层次：一级（氨基酸序列），二级（靠氢键维持的α‑螺旋和β‑折叠），三级（由氢键、离子键、二硫键和疏水相互作用稳定下来的三维折叠）和四级（不止一条多肽链）。酶活性位点的特定形状就是由三级结构决定的。
Water serves as an excellent solvent, has a high specific heat capacity and a high latent heat of vaporisation, and exhibits strong cohesion – properties that make it vital for transport, temperature regulation and supporting life processes.
水是优良的溶剂，具有高比热容和高汽化潜热，内聚力强——这些性质使水对运输、温度调节和维持生命过程至关重要。
2. Cell Ultrastructure and Function | 细胞超微结构与功能
Prokaryotic cells (bacteria) lack a true nucleus and membrane‑bound organelles; they possess 70S ribosomes, a circular DNA molecule and may have plasmids. Eukaryotic cells contain a double‑membrane nucleus, linear DNA associated with histones and 80S ribosomes.
原核细胞（细菌）没有真正的细胞核和膜包被的细胞器；它们有 70S 核糖体、环状 DNA 分子，并可能含有质粒。真核细胞含有双层膜的细胞核、与组蛋白结合的线性 DNA 和 80S 核糖体。
Be able to describe the structure and function of key organelles: mitochondria (aerobic respiration), chloroplasts (photosynthesis), rough endoplasmic reticulum (protein synthesis and transport), smooth ER (lipid synthesis), Golgi apparatus (modifying and packaging proteins), lysosomes (digestion), ribosomes (translation) and centrioles (spindle fibre organisation).
要能描述关键细胞器的结构与功能：线粒体（有氧呼吸）、叶绿体（光合作用）、粗糙内质网（蛋白质合成与运输）、光滑内质网（脂质合成）、高尔基体（蛋白质修饰与包装）、溶酶体（消化）、核糖体（翻译）以及中心粒（纺锤丝的组织）。
Light microscopes and electron microscopes (TEM and SEM) are used for different resolutions. Always convert units correctly when calculating magnification: magnification = image size ÷ actual size. Cell fractionation and differential centrifugation separate organelles based on size and density.
光学显微镜与电子显微镜（透射电镜和扫描电镜）用于不同的分辨率。计算放大倍数时务必要正确换算单位：放大倍数 = 图像尺寸 ÷ 实际尺寸。细胞分级分离和差速离心可以根据大小和密度分离细胞器。
3. Membrane Transport and Exchange | 膜运输与物质交换
The fluid‑mosaic model describes membranes as a phospholipid bilayer with embedded proteins (channel and carrier proteins), cholesterol (regulating fluidity) and glycoproteins/glycolipids (cell recognition). The arrangement is dynamic, not static.
流动镶嵌模型将膜描述为磷脂双分子层，其中嵌有蛋白质（通道蛋白和载体蛋白）、胆固醇（调节流动性）和糖蛋白/糖脂（细胞识别）。这种排列是动态的，而非静止不动。
Passive transport requires no metabolic energy. Simple diffusion occurs down a concentration gradient; facilitated diffusion uses channel or carrier proteins. Osmosis is the net movement of water from a region of higher water potential (ψ) to a lower water potential, influenced by solute and pressure potentials (ψ = ψs + ψp).
被动运输不需要代谢能量。简单扩散顺浓度梯度进行；协助扩散利用通道蛋白或载体蛋白。渗透作用是水从较高水势(ψ)区域向较低水势区域的净移动，受溶质势和压力势的影响 (ψ = ψs + ψp)。
Active transport uses ATP to move substances against their concentration gradient via carrier proteins. Co‑transport mechanisms, such as the absorption of glucose in the ileum, couple the movement of Na⁺ down its gradient to the uptake of glucose. Bulk transport (endocytosis and exocytosis) moves large molecules.
主动运输利用 ATP，通过载体蛋白逆浓度梯度移动物质。协同转运机制——例如小肠对葡萄糖的吸收——将 Na⁺ 顺梯度移动与葡萄糖的摄取耦合起来。大分子则通过胞吞和胞吐进行批量运输。
4. Enzymes and Metabolic Pathways | 酶与代谢途径
Enzymes are globular proteins with a specific active site complementary to the substrate. The induced‑fit model states that the active site changes shape slightly as the substrate binds, stressing bonds and lowering activation energy.
酶是球状蛋白，拥有与底物互补的特异性活性位点。诱导契合模型认为，当底物结合时，活性位点形状略微改变，使化学键受到应力，从而降低活化能。
Temperature, pH, enzyme concentration and substrate concentration all affect the rate of enzyme‑catalysed reactions. You must be able to sketch and interpret graphs showing initial rate of reaction against each factor, explaining the shape with reference to kinetic energy, denaturation and saturation of active sites.
温度、pH、酶浓度和底物浓度都会影响酶促反应的速率。你必须能够绘制并解读反应初速率针对各因素的曲线图，并用动能、变性及活性位点饱和来解释曲线形状。
Competitive inhibitors bind at the active site and can be overcome by increasing substrate concentration. Non‑competitive inhibitors bind elsewhere (allosteric site), altering the shape of the active site; increasing substrate concentration does not reverse the effect. End‑product inhibition is a form of non‑competitive regulation.
竞争性抑制剂结合于活性位点，可通过提高底物浓度来克服。非竞争性抑制剂结合在其他部位（别构位点），改变活性位点形状；提高底物浓度不会逆转其影响。终产物抑制是一种非竞争性调控形式。
5. Nucleic Acids and Protein Synthesis | 核酸与蛋白质合成
DNA is a double helix composed of deoxyribonucleotides joined by phosphodiester bonds. Two strands are held together by hydrogen bonds between complementary base pairs: adenine‑thymine (two H‑bonds) and cytosine‑guanine (three H‑bonds). RNA is single‑stranded, contains ribose and uracil instead of thymine.
DNA 为双螺旋，由脱氧核糖核苷酸通过磷酸二酯键连接而成。两条链通过互补碱基对之间的氢键维系：腺嘌呤‑胸腺嘧啶（两个氢键），胞嘧啶‑鸟嘌呤（三个氢键）。RNA 为单链，含有核糖，用尿嘧啶替代胸腺嘧啶。
DNA replication is semi‑conservative, as shown by the Meselson–Stahl experiment. Helicase unwinds the double helix; DNA polymerase adds complementary nucleotides in the 5′ to 3′ direction; ligase joins Okazaki fragments on the lagging strand.
DNA 复制是半保留的，由梅塞尔森–斯塔尔实验证明。解旋酶解开双螺旋；DNA 聚合酶沿 5′ 到 3′ 方向添加互补核苷酸；连接酶将滞后链上的冈崎片段连接起来。
During transcription, RNA polymerase produces a pre‑mRNA molecule that is spliced to remove introns in eukaryotes. Translation at ribosomes uses mRNA codons, tRNA anticodons and peptide bond formation to assemble a polypeptide. Substitution, insertion and deletion mutations can create frameshifts with drastic effects on the amino acid sequence.
转录过程中，RNA 聚合酶产生前体 mRNA，真核生物中前体 mRNA 经过剪接去除内含子。翻译在核糖体上进行，利用 mRNA 密码子、tRNA 反密码子和肽键的形成来组装多肽。置换、插入和缺失突变可产生移码，对氨基酸序列产生巨大影响。
6. Cell Cycle and Genetics | 细胞周期与遗传学
The cell cycle consists of interphase (G₁, S, G₂) and mitosis followed by cytokinesis. Mitosis produces two genetically identical diploid daughter cells for growth and repair. Meiosis involves two divisions (meiosis I and II), halving the chromosome number and generating genetic variation through crossing over and independent assortment.
细胞周期包括间期（G₁、S、G₂）以及有丝分裂和随后的胞质分裂。有丝分裂产生两个遗传上完全相同的二倍体子细胞，用于生长和修复。减数分裂包含两次分裂（减数 I 和减数 II），将染色体数目减半，并通过交叉互换和独立分配产生遗传变异。
Stem cells differ in potency: totipotent (can give rise to a whole organism), pluripotent (all cell types of an embryo), multipotent (several cell types) and unipotent (one type). The use of embryonic stem cells raises ethical issues that need to be evaluated.
干细胞的分化潜能不同：全能性（可发育成完整个体）、多能性（胚胎的全部细胞类型）、多潜能（几种细胞类型）和单能性（一种类型）。胚胎干细胞的使用会带来需要权衡的伦理问题。
7. Inheritance and Gene Expression | 遗传与基因表达
Monohybrid and dihybrid crosses yield characteristic phenotypic ratios (3:1, 9:3:3:1) under Mendelian independent assortment. Learn to work with co‑dominance (e.g. blood groups Iᴬ, Iᴮ, i) and sex‑linked traits (X‑linked recessive) where males are more frequently affected.
在孟德尔独立分配定律下，单基因杂交和双基因杂交会产生典型的表型比例（3:1，9:3:3:1）。要学会处理共显性（例如血型 Iᴬ, Iᴮ, i）和性连锁性状（X 染色体隐性），男性患病率更高。
Autosomal linkage leads to deviations from expected ratios because linked genes are inherited together unless crossing over separates them. The chi‑squared test is used to determine whether observed ratios differ significantly from expected.
常染色体连锁会导致偏离预期比率，因为连锁基因倾向于一起遗传，除非发生交叉互换将它们分开。卡方检验用于判断观测比例是否与预期比例有显著差异。
Epigenetic changes, such as DNA methylation and histone modification, can alter gene expression without changing the DNA sequence. These changes can be
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