IB & WJEC Biology: Last-Minute Revision Notes | IB 与 WJEC 生物考前冲刺笔记

📚 IB & WJEC Biology: Last-Minute Revision Notes | IB 与 WJEC 生物考前冲刺笔记

Whether you are sitting IB Biology or WJEC Biology exams, the final hours before the test are all about consolidating high-yield content, spotting common traps, and strengthening your command of core principles. This set of revision notes distils essential topics into concise, bilingual summaries that help you review quickly and accurately. Each section pairs an English explanation with its Chinese counterpart so you can cross-reference and reinforce your understanding in two languages. Use these notes to sharpen your recall, clarify concepts, and walk into the exam hall with confidence.

无论你参加的是 IB 生物还是 WJEC 生物考试，考前最后几小时的关键在于巩固高回报内容、识别常见陷阱并加强对核心原理的掌握。这套复习笔记将核心主题浓缩为简洁的双语摘要，帮助你快速准确地回顾。每个要点先提供英文解释，再给出对应的中文阐述，方便你通过双语交叉对照加深理解。利用这些笔记强化记忆、厘清概念，自信地走进考场。

1. Cell Structure & Function | 细胞结构与功能

Eukaryotic cells contain membrane-bound organelles such as the nucleus, mitochondria, rough and smooth endoplasmic reticulum, Golgi apparatus, lysosomes, and (in plants) chloroplasts and a large central vacuole. Prokaryotic cells lack a nucleus and membrane-bound organelles, having instead a single circular chromosome, 70S ribosomes, and often a cell wall made of peptidoglycan. Both cell types share a plasma membrane, cytoplasm, and ribosomes, supporting the idea of common ancestry.

真核细胞含有由膜包被的细胞器，如细胞核、线粒体、粗面与滑面内质网、高尔基体、溶酶体，以及（植物细胞中的）叶绿体和大液泡。原核细胞没有细胞核和膜包被的细胞器，取而代之的是单个环状染色体、70S 核糖体，通常还具有由肽聚糖构成的细胞壁。两类细胞都拥有质膜、细胞质和核糖体，这支持了共同祖先的观点。

For exam success, be able to label a typical animal and plant cell diagram, and compare prokaryotic and eukaryotic cells in a table. The table should cover size, nucleus, membrane-bound organelles, ribosome type, and cell wall composition. Remember that viruses are non-cellular; they have a protein capsid and nucleic acid core and can only reproduce inside host cells.

为了在考试中拿分，要能标注典型的动物细胞和植物细胞结构图，并能用表格对比原核细胞与真核细胞。表格应涵盖大小、细胞核、膜包被细胞器、核糖体类型以及细胞壁组成。记住，病毒是非细胞结构，具有蛋白质衣壳和核酸核心，只能在宿主细胞内繁殖。

Feature	Prokaryotic	Eukaryotic
Nucleus	Absent	Present
Membrane-bound organelles	None	Many (mitochondria, ER, etc.)
Ribosomes	70S	80S
Cell wall	Peptidoglycan (bacteria)	Cellulose (plants), chitin (fungi)

2. Biological Molecules | 生物分子

Carbohydrates, lipids, proteins, and nucleic acids are the four major classes of biological molecules. Monosaccharides such as glucose are joined by glycosidic bonds to form disaccharides (maltose, sucrose) and polysaccharides (starch, glycogen, cellulose). Lipids are made of glycerol and fatty acids; triglycerides are energy storage molecules, while phospholipids form the bilayer of cell membranes due to their amphipathic nature.

碳水化合物、脂质、蛋白质和核酸是四大类生物分子。单糖（如葡萄糖）通过糖苷键连接成二糖（麦芽糖、蔗糖）和多糖（淀粉、糖原、纤维素）。脂质由甘油和脂肪酸构成；甘油三酯是能量储存分子，而磷脂则因其两亲性构成细胞膜的双层结构。

Proteins are polymers of amino acids linked by peptide bonds. There are four levels of protein structure: primary (linear sequence), secondary (alpha helices and beta pleated sheets via hydrogen bonds), tertiary (3D folding due to hydrophobic interactions, disulfide bonds, ionic bonds), and quaternary (more than one polypeptide chain, e.g. haemoglobin). Enzyme activity depends on the precise tertiary shape of the active site.

蛋白质是由氨基酸通过肽键连接而成的聚合物。蛋白质结构分为四个层次：一级结构（线性序列）、二级结构（通过氢键形成的 α-螺旋和 β-折叠）、三级结构（由疏水作用、二硫键、离子键等导致的三维折叠）和四级结构（多条多肽链的组合，如血红蛋白）。酶的活性依赖于活性位点精确的三级结构。

For nucleic acids, recall that DNA is a double helix of nucleotides (deoxyribose sugar, phosphate, nitrogenous base A, T, C, G) held by hydrogen bonds and phosphodiester backbones. RNA uses ribose and uracil instead of thymine. ATP is the energy currency, composed of adenine, ribose, and three phosphate groups; energy is released when the terminal phosphate is hydrolysed.

核酸方面，记住 DNA 是由核苷酸（脱氧核糖、磷酸、含氮碱基 A、T、C、G）组成的双螺旋，通过氢键和磷酸二酯骨架维持结构。RNA 使用核糖，并以尿嘧啶代替胸腺嘧啶。ATP 是能量货币，由腺嘌呤、核糖和三个磷酸基团组成；水解末端磷酸基团时释放能量。

3. Enzymes | 酶

Enzymes are biological catalysts that lower activation energy without being consumed. The lock-and-key model suggests a perfect fit between substrate and active site, while the induced-fit model states that the active site changes shape to accommodate the substrate. Factors affecting enzyme activity include temperature, pH, substrate concentration, and inhibitor presence.

酶是降低活化能而不被消耗的生物催化剂。锁钥模型认为底物与活性位点完全契合，而诱导契合模型则指出活性位点会改变形状以容纳底物。影响酶活性的因素有温度、pH、底物浓度以及抑制剂的存在。

Competitive inhibitors resemble the substrate and compete for the active site; their effect can be overcome by increasing substrate concentration. Non-competitive inhibitors bind to an allosteric site, altering the enzyme’s shape and reducing V_max regardless of substrate concentration. Denaturation occurs when extreme pH or high temperature disrupts hydrogen and ionic bonds, permanently altering the active site.

竞争性抑制剂与底物结构相似，竞争活性位点；增加底物浓度可克服其抑制效应。非竞争性抑制剂结合于别构位点，改变酶的形状，无论底物浓度如何都会降低 V_max。当极端的 pH 或高温破坏了氢键和离子键时，酶发生变性，活性位点永久改变。

In practical assessments, you may need to design an experiment to investigate the effect of a variable on enzyme activity (e.g. measuring the rate of catalase breaking down hydrogen peroxide). Always identify independent, dependent, and control variables, state how you would measure the rate, and consider repeats for reliability.

在实验评估中，你可能需要设计实验探究某一变量对酶活性的影响（如测量过氧化氢酶分解过氧化氢的速率）。始终要明确自变量、因变量和控制变量，说明如何测量速率，并考虑重复实验以保证可靠性。

4. Cell Membranes & Transport | 细胞膜与运输

The fluid mosaic model describes the plasma membrane as a phospholipid bilayer with embedded proteins, cholesterol (in animals), and glycoproteins. Phospholipids can move laterally, giving the membrane fluidity. Transport across membranes occurs via passive processes (diffusion, facilitated diffusion, osmosis) and active transport, which requires ATP.

流动镶嵌模型将质膜描述为磷脂双分子层，其中嵌有蛋白质、胆固醇（动物细胞）和糖蛋白。磷脂可侧向移动，赋予膜流动性。跨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。

Osmosis is the net movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane. Water potential is affected by solute concentration and pressure. In plant cells, turgor pressure opposes further water uptake when the cell is turgid; in animal cells, lysis can occur in hypotonic solutions without a cell wall.

渗透是水分子通过部分透性膜从较高水势区域向较低水势区域的净移动。水势受溶质浓度和压力的影响。在植物细胞中，当细胞处于饱满状态时，膨压会阻止水分进一步进入；动物细胞无细胞壁，在低渗溶液中可能发生裂解。

Bulk transport (endocytosis and exocytosis) allows large molecules to cross the membrane via vesicles. Endocytosis engulfs material by infolding of the membrane; exocytosis secretes substances by vesicle fusion with the membrane. These processes also require energy.

批量运输（胞吞和胞吐）使大分子能够通过囊泡跨越细胞膜。胞吞通过膜内陷包裹物质；胞吐则是囊泡与膜融合，将物质分泌出去。这些过程同样需要能量。

5. DNA Replication, Transcription & Translation | DNA 复制、转录与翻译

DNA replication is semi-conservative: each new DNA molecule consists of one original strand and one newly synthesised strand. The enzyme helicase unwinds the double helix, and DNA polymerase adds complementary nucleotides in a 5′ to 3′ direction. The leading strand is synthesised continuously, while the lagging strand is built in Okazaki fragments, later joined by DNA ligase.

DNA 复制是半保留的：每个新的 DNA 分子由一条原始链和一条新合成的链组成。解旋酶解开双螺旋，DNA 聚合酶沿 5’→3′ 方向添加互补核苷酸。前导链连续合成，后随链则以冈崎片段的形式合成，随后由 DNA 连接酶连接。

Transcription produces mRNA from a DNA template. RNA polymerase binds to the promoter, unwinds the DNA, and assembles complementary RNA nucleotides (uracil replaces thymine). In eukaryotes, pre-mRNA undergoes splicing to remove introns before leaving the nucleus. Translation occurs at ribosomes, where tRNA molecules with anticodons match mRNA codons, bringing specific amino acids to form a polypeptide chain.

转录以 DNA 为模板合成 mRNA。RNA 聚合酶与启动子结合，解开 DNA，并按碱基互补原则组装 RNA 核苷酸（尿嘧啶替代胸腺嘧啶）。在真核生物中，前体 mRNA 需经过剪接去除内含子后才能离开细胞核。翻译在核糖体进行，带有反密码子的 tRNA 识别 mRNA 上的密码子，携带特定氨基酸延伸多肽链。

The genetic code is degenerate (more than one codon can code for the same amino acid) and universal. Be prepared to interpret a codon table. Mutations such as substitution, insertion, or deletion can alter the amino acid sequence, potentially affecting protein function.

遗传密码具有简并性（多个密码子可编码同一种氨基酸）和通用性。要会解读密码子表。替换、插入或缺失等突变可改变氨基酸序列，可能影响蛋白质功能。

6. Cell Division & Genetics | 细胞分裂与遗传学

Mitosis produces two genetically identical diploid daughter cells and is used for growth, repair, and asexual reproduction. The stages are prophase, metaphase, anaphase, and telophase (followed by cytokinesis). Meiosis produces four genetically diverse haploid gametes through two divisions. Key events include crossing over in prophase I and independent assortment in metaphase I, both generating variation.

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、修复和无性生殖。阶段包括前期、中期、后期和末期（随后是胞质分裂）。减数分裂通过两次分裂产生四个遗传多样的单倍体配子。关键事件包括前期 I 的交叉互换和中期 I 的独立分配，两者都产生变异。

Mendelian genetics relies on the segregation of alleles during gamete formation. Use Punnett squares to predict genotypic and phenotypic ratios for monohybrid and dihybrid crosses. Understand terms such as dominant, recessive, homozygous, heterozygous, genotype, and phenotype. Sex-linked traits (e.g. colour blindness) are carried on the X chromosome, leading to different inheritance patterns in males and females.

孟德尔遗传学基于配子形成时等位基因的分离。使用庞纳特方格预测单基因杂交和双基因杂交的基因型比例与表现型比例。要理解显性、隐性、纯合、杂合、基因型和表现型等术语。伴性遗传性状（如色盲）由 X 染色体携带，导致男女遗传模式不同。

Pedigree charts can be analysed to determine inheritance patterns (autosomal dominant, autosomal recessive, X-linked recessive). Symbols represent individuals; shaded shapes usually indicate affected individuals. Practice interpreting pedigrees for common exam questions.

可通过系谱图分析遗传模式（常染色体显性、常染色体隐性、X 连锁隐性）。符号代表个体；阴影通常表示患病个体。针对常见考题，多练习解读系谱图。

7. Cellular Respiration & Photosynthesis | 细胞呼吸与光合作用

Cellular respiration breaks down glucose to release ATP. Glycolysis occurs in the cytoplasm, producing pyruvate and a small amount of ATP and NADH. In aerobic respiration, pyruvate enters the mitochondrion for the link reaction, Krebs cycle, and oxidative phosphorylation, yielding up to 38 ATP per glucose. Anaerobic respiration in animals produces lactate; in yeast and plants, it produces ethanol and CO₂.

细胞呼吸分解葡萄糖释放 ATP。糖酵解在细胞质中进行，产生丙酮酸以及少量 ATP 和 NADH。在有氧呼吸中，丙酮酸进入线粒体进行连接反应、克雷布斯循环和氧化磷酸化，每分子葡萄糖最多生成 38 个 ATP。无氧呼吸在动物中产生乳酸，在酵母和植物中产生乙醇和 CO₂。

Photosynthesis captures light energy to synthesise organic molecules. Light-dependent reactions occur in the thylakoid membranes: light splits water (photolysis), generating O₂, ATP, and NADPH. The Calvin cycle (light-independent) uses ATP and NADPH to fix CO₂ into glucose in the stroma. Key factors limiting photosynthesis include light intensity, carbon dioxide concentration, and temperature.

光合作用捕获光能合成有机物。光依赖反应发生在类囊体膜上：光能分解水（光解），产生 O₂、ATP 和 NADPH。卡尔文循环（碳固定）在基质中利用 ATP 和 NADPH 将 CO₂ 固定为葡萄糖。限制光合作用的主要因素包括光照强度、二氧化碳浓度和温度。

The overall word equations to memorise:

Glucose + Oxygen → Carbon dioxide + Water (+ ATP energy) for respiration, and

Carbon dioxide + Water → Glucose + Oxygen (in the presence of light and chlorophyll) for photosynthesis.

要记住的总反应方程式：

葡萄糖 + 氧气 → 二氧化碳 + 水 (+ ATP 能量) （呼吸作用）

二氧化碳 + 水 → 葡萄糖 + 氧气 （光合作用，需要光和叶绿体）

8. Evolution & Natural Selection | 进化与自然选择

Natural selection acts on phenotypic variation within a population. Individuals with advantageous traits are more likely to survive and reproduce, passing on those alleles. Over generations, the allele frequency for beneficial traits increases, leading to adaptation. Darwin’s theory is supported by fossil records, homologous structures, and DNA evidence.

自然选择作用于种群内的表现型变异。拥有有利性状的个体更有可能存活并繁殖，将这些等位基因传递下去。经过数代，有利性状的等位基因频率上升，导致适应。达尔文学说得到化石记录、同源结构和 DNA 证据的支持。

Antibiotic resistance in bacteria is a prime example of natural selection. A mutation confers resistance; in the presence of antibiotics, sensitive bacteria die while resistant ones thrive and multiply, shifting the population. Understanding this mechanism helps explain why completing antibiotic courses and cautious use are essential.

细菌的抗生素耐药性是自然选择的典型例子。突变产生耐药性；在抗生素存在时，敏感菌死亡，耐药菌存活并大量繁殖，使种群发生转变。理解这一机制有助于解释为什么完成整个疗程和谨慎使用抗生素至关重要。

Speciation occurs when populations become reproductively isolated. Allopatric speciation happens due to geographical barriers; sympatric speciation occurs without physical separation, often through polyploidy or behavioural changes. Cladistics uses shared derived characteristics to construct phylogenetic trees, showing evolutionary relationships.

物种形成发生在种群生殖隔离时。异域物种形成由地理屏障导致；同域物种形成则无物理隔离，常通过多倍体或行为变化实现。支序分类学利用共享衍征构建系统发育树，展示进化关系。

9. Ecology & Energy Flow | 生态学与能量流动

Ecosystems consist of communities interacting with their abiotic environment. Energy enters most ecosystems through sunlight and is converted by producers (plants) via photosynthesis. Energy flows unidirectionally through trophic levels, with only about 10% transferred from one level to the next; the rest is lost as heat through respiration or remains in uneaten parts. This is represented in pyramids of energy, which are always upright.

生态系统由群落与其非生物环境相互作用构成。能量通过阳光进入大多数生态系统，由生产者（植物）通过光合作用转化。能量沿营养级单向流动，仅约 10% 的能量从一个营养级传递到下一个；其余以呼吸产热或未食部分的形式散失。这体现在能量金字塔上，而且能量金字塔总是正立的。

Nutrient cycles (carbon and nitrogen) are essential for life. The carbon cycle involves photosynthesis, respiration, decomposition, and combustion. The nitrogen cycle includes nitrogen fixation, nitrification, assimilation, ammonification, and denitrification. Be able to label diagrams showing these processes and the roles of different bacteria.

物质循环（碳循环和氮循环）对生命至关重要。碳循环包括光合作用、呼吸作用、分解作用和燃烧。氮循环包括固氮作用、硝化作用、同化作用、氨化作用和反硝化作用。要能标注显示这些过程的示意图，并说明不同细菌的角色。

Ecological techniques such as quadrats and transects are used to estimate population sizes and distribution. Use the Lincoln index (capture-mark-recapture) for motile organisms. Simpson’s diversity index gives a measure of biodiversity; higher values indicate greater diversity and usually a more stable ecosystem.

样方和样带等生态学技术用于估算种群大小和分布。对于活动性生物，使用林肯指数（捕获-标记-再捕获法）。辛普森多样性指数衡量生物多样性；数值越高表示多样性越高，通常生态系统也越稳定。

10. Human Physiology: Key Systems | 人体生理学：关键系统

The circulatory system includes the heart, blood vessels, and blood. The heart is a double pump; the right side pumps deoxygenated blood to the lungs, the left side pumps oxygenated blood to the body. Be able to trace the path of blood through the heart, naming chambers (atria, ventricles), valves (tricuspid, bicuspid, semilunar), and major vessels (aorta, vena cava, pulmonary artery, pulmonary vein).

循环系统包括心脏、血管和血液。心脏是一个双泵：右侧将缺氧血泵至肺部，左侧将富氧血泵至全身。要能追踪血液流经心脏的路径，说出心腔（心房、心室）、瓣膜（三尖瓣、二尖瓣、半月瓣）和主要血管（主动脉、腔静脉、肺动脉、肺静脉）的名称。

The respiratory system exchanges gases via the alveoli, which have thin walls, large surface area, and a rich capillary network. Breathing involves the diaphragm and intercostal muscles. Gas exchange occurs by diffusion down concentration gradients. Haemoglobin binds oxygen in the lungs and releases it in tissues; the Bohr effect means that higher CO₂ concentration lowers haemoglobin’s affinity for oxygen.

呼吸系统通过肺泡进行气体交换，肺泡壁薄、表面积大且具有丰富的毛细血管网。呼吸涉及膈肌和肋间肌。气体交换通过扩散顺着浓度梯度进行。血红蛋白在肺部结合氧，在组织释放氧；玻尔效应表明，较高的 CO₂ 浓度会降低血红蛋白对氧的亲和力。

The immune system defends against pathogens. Non-specific defences include skin, mucus, and phagocytes. Specific immunity involves lymphocytes: B cells produce antibodies (humoral response), while T cells help destroy infected cells (cell-mediated response). Vaccination stimulates memory cell production for long-term immunity.

免疫系统防御病原体。非特异性防御包括皮肤、粘液和吞噬细胞。特异性免疫涉及淋巴细胞：B 细胞产生抗体（体液免疫），T 细胞协助摧毁受感染细胞（细胞免疫）。疫苗接种可刺激记忆细胞生成，产生长期免疫力。

The nervous system uses neurones to transmit electrical impulses. A reflex arc includes a receptor, sensory neurone, relay neurone in the CNS, motor neurone, and effector. Synaptic transmission uses neurotransmitters such as acetylcholine. The endocrine system releases hormones (e.g. insulin, glucagon) to regulate blood glucose; negative feedback maintains homeostasis.

神经系统利用神经元传递电冲动。反射弧包括感受器、感觉神经元、中枢神经系统中的联络神经元、运动神经元和效应器。突触传递使用乙酰胆碱等神经递质。内分泌系统释放激素（如胰岛素、胰高血糖素）来调节血糖；负反馈维持稳态。

11. Plant Biology: Transport & Growth | 植物生物学：运输与生长

Xylem vessels transport water and mineral ions from roots to leaves. The cohesion-tension theory explains water movement: transpiration from leaves creates tension, pulling water up the xylem as a continuous column due to cohesion between water molecules. Phloem transports sugars (mainly sucrose) by translocation from sources to sinks, using the pressure-flow hypothesis.

木质部导管将水分和矿物质离子从根部运往叶片。内聚力-张力学说解释了水分运输：叶片的蒸腾作用产生张力，而水分子间的内聚力使水分在木质部中形成连续水柱，被向上拉动。韧皮部则通过压力流假说以转运的方式将糖类（主要是蔗糖）从源运输到库。

Factors affecting transpiration rate include light intensity, temperature, humidity, and air movement. A potometer can be used to estimate transpiration rate, but it measures water uptake, not transpiration directly. Be prepared to interpret graphs showing how these factors change transpiration.

影响蒸腾速率的因素有光照强度、温度、湿度和空气流动。蒸腾计可用于估算蒸腾速率，但它测量的是吸水速率，而非直接测量蒸腾。要会解读显示这些因素如何改变蒸腾作用的图表。

Plant growth is regulated by hormones such as auxins, which promote cell elongation and are involved in phototropism and gravitropism. In shoots, higher auxin concentration on the shaded side causes cells to elongate more, bending the shoot toward light. In roots, high auxin inhibits cell elongation, causing the root to bend downwards.

植物生长受激素调控，如生长素促进细胞伸长，并参与向光性和向地性。在茎中，背光侧生长素浓度较高，使细胞伸长更多，导致茎向光弯曲。在根中，高浓度生长素抑制细胞伸长，使根向下弯曲。

12. Exam Technique & Common Pitfalls | 考试技巧与常见陷阱

In both IB and WJEC exams, marks are lost when students do not read command terms carefully. ‘Explain’ requires a scientific reason, ‘describe’ asks for what you see, ‘compare’ needs similarities and differences, and ‘evaluate’ expects a balanced judgement with evidence. Time management is crucial; allocate roughly one minute per mark and leave time to check answers.

无论是 IB 还是 WJEC 考试，学生因未仔细审题而失分的情况十分常见。“解释”要求给出科学原因，“描述”问的是观察到的现象，“比较”需要指出相同点和不同点，而“评价”则期待基于证据的平衡判断。时间管理至关重要；大约每分分配一分钟，并留出时间检查答案。

Draw diagrams with a pencil, label clearly with straight lines, and avoid arrowheads unless indicating direction. Use correct scientific terminology at all times. For calculations, show your working, include units, and pay attention to significant figures. In data analysis questions, always quote figures from the graph or table to support your answer.

画图要用铅笔，标注用直线并清晰书写，除非标示方向否则不要画箭头。始终使用正确的科学术语。在计算题中，写出推导过程，标明单位，注意有效数字。在数据分析题中，务必引用图表中的数值来支持你的答案。

Common pitfalls include confusing diffusion with osmosis, forgetting that enzymes are not used up in reactions, mixing up transcription and translation, and stating that ‘respiration is breathing’. Make a quick mental checklist of these misconceptions before entering the exam. Stay calm, breathe steadily, and trust your revision.

常见陷阱包括混淆扩散与渗透、忘记酶在反应中不被消耗、搞混转录与翻译，以及误认为“呼吸作用就是呼吸运动”。进入考场前在心里快速过一遍这些常见误区。保持冷静、稳定呼吸，相信你的复习成果。

Published by TutorHao | Biology Revision Series | aleveler.com

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IB & WJEC Biology: Last-Minute Revision Notes | IB 与 WJEC 生物考前冲刺笔记