📚 IB & OCR Biology: Last-Minute Sprint Notes | IB & OCR 生物：考前冲刺笔记
Whether you’re sitting IB Higher Level or OCR A Biology, the final days before the exam demand razor-sharp recall of core principles. This sprint guide distils the key topics that overlap both specifications — from biomolecules to ecosystems — into concise, bilingual summaries designed for rapid revision. Use it to close knowledge gaps, reinforce command terms, and walk into the exam hall with confidence.
无论你参加的是 IB 高阶生物还是 OCR A 生物考试，考前最后几天都需要对核心原理有刀锋般锐利的记忆。这份冲刺笔记提炼了两套大纲中重叠的关键主题——从生物分子到生态系统——浓缩成适合快速复习的中英双语要点。用它来补足知识盲区、强化指令术语，并自信地走进考场。
1. Cell Theory & Microscopy | 细胞学说与显微镜
All living organisms are composed of cells, which arise from pre-existing cells. In both IB and OCR, you must know the differences between prokaryotic and eukaryotic cells, as well as how to calculate magnification using the formula Magnification = Image size / Actual size.
所有生物体都由细胞组成，细胞来自已有的细胞。在 IB 和 OCR 中，你必须掌握原核细胞与真核细胞的区别，以及如何使用公式 放大倍数 = 图像大小 / 实际大小 进行计算。
Distinguish between light and electron microscopes: light microscopes can view living specimens and colour but have lower resolution, while electron microscopes offer far greater resolution but kill the sample. Know how to interpret micrographs and use the scale bar for measurements.
区分光学显微镜和电子显微镜：光学显微镜可观察活体样本并显示颜色，但分辨率较低；电子显微镜分辨率极高却会杀死样品。务必学会解读显微照片并使用比例尺进行测量。
2. Membrane Structure & Transport | 膜结构与运输
The fluid mosaic model describes the plasma membrane as a phospholipid bilayer with embedded proteins, cholesterol (in animal cells), and glycoproteins. The hydrophilic phosphate heads face outward while hydrophobic fatty acid tails face inward, creating a selectively permeable barrier.
流动镶嵌模型将细胞膜描述为由磷脂双分子层与嵌入的蛋白质、胆固醇（动物细胞）及糖蛋白组成。亲水的磷酸头朝向外侧，疏水的脂肪酸尾部朝向内部，形成选择透过性屏障。
Understand passive transport (diffusion, facilitated diffusion, osmosis) and active transport requiring ATP. In IB, you must also explain endocytosis and exocytosis, and how the sodium-potassium pump generates a resting potential in neurons — a detail echoed in OCR’s communication topic.
理解被动运输（简单扩散、易化扩散、渗透）和需要 ATP 的主动运输。在 IB 中，你还需要解释胞吞与胞吐作用，以及钠钾泵如何建立神经元静息电位——OCR 的神经通讯单元也涉及此细节。
3. Biological Molecules | 生物分子
Carbohydrates: monosaccharides like glucose (C₆H₁₂O₆) are energy sources; disaccharides such as sucrose form via condensation reactions; polysaccharides include starch, glycogen, and cellulose. Know the test for reducing sugars (Benedict’s) and starch (iodine).
碳水化合物：单糖如葡萄糖（C₆H₁₂O₆）是能量来源；二糖如蔗糖通过缩合反应形成；多糖包括淀粉、糖原和纤维素。掌握还原糖（本尼迪特试剂）和淀粉（碘液）的检测法。
Lipids are composed of glycerol and three fatty acids, joined by ester bonds. They provide insulation, energy storage, and form phospholipid bilayers. Proteins have four structural levels, determined by amino acid sequence; use the Biuret test for detection.
脂质由甘油和三个脂肪酸通过酯键结合而成，具有保温、储能和构成磷脂双层的功能。蛋白质有四级结构，由氨基酸序列决定；用双缩脲检测可识别蛋白质。
4. Enzymes | 酶
Enzymes are globular proteins that lower activation energy. The induced-fit model explains how the active site moulds around the substrate. Be able to describe the effect of temperature, pH, and substrate concentration on enzyme activity, and draw the characteristic graph shapes for both specifications.
酶是能降低活化能的球状蛋白质。诱导契合模型说明了活性中心如何围绕底物发生形变。务必能描述温度、pH 和底物浓度对酶活性的影响，并能画出 IB 和 OCR 考试中都会出现的典型曲线图。
Competitive inhibitors bind to the active site; non-competitive inhibitors bind elsewhere and change the shape of the active site. End-product inhibition is a key example of negative feedback in metabolic pathways. Know how immobilised enzymes are used in industrial lactose-free milk production.
竞争性抑制剂结合于活性位点；非竞争性抑制剂结合于别处并改变活性位点形状。终产物抑制是代谢途径中负反馈的典型例子。掌握固定化酶在工业无乳糖牛奶生产中的应用。
5. DNA Replication, Transcription & Translation | DNA 复制、转录与翻译
DNA replication is semi-conservative, catalysed by helicase (unwinds) and DNA polymerase (adds nucleotides in the 5′ to 3′ direction). In IB and OCR, you must be able to explain the Meselson-Stahl experiment that proved this mechanism.
DNA 复制是半保留的，由解旋酶（解链）和 DNA 聚合酶（沿 5′ 到 3′ 方向添加核苷酸）催化。在 IB 和 OCR 考试中，你必须能解释证明该机制的梅塞尔森-斯塔尔实验。
During transcription, RNA polymerase synthesises mRNA from the template strand. Translation involves ribosomes, tRNA anticodons, and the formation of polypeptide chains. Be precise with base pairing: adenine with thymine (DNA) or uracil (RNA), and cytosine with guanine.
转录过程中，RNA 聚合酶以模板链合成 mRNA。翻译涉及核糖体、tRNA 反密码子及多肽链的形成。碱基配对要准确：腺嘌呤与胸腺嘧啶（DNA）或尿嘧啶（RNA）配对，胞嘧啶与鸟嘌呤配对。
6. Cell Division: Mitosis & Meiosis | 细胞分裂：有丝分裂与减数分裂
Mitosis produces two genetically identical diploid daughter cells for growth and repair. It consists of prophase, metaphase, anaphase, and telophase (cytokinesis). Be able to recognise each stage in micrographs and root tip squashes.
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。它包括前期、中期、后期和末期（胞质分裂）。要能识别显微图像及根尖压片中的各个时期。
Meiosis halves the chromosome number to produce haploid gametes, introducing genetic variation through independent assortment and crossing over. Both IB and OCR require you to explain how non-disjunction can lead to conditions such as Down syndrome (trisomy 21).
减数分裂将染色体数目减半，产生单倍体配子，并通过自由组合和交叉互换引入遗传变异。IB 和 OCR 都要求你解释染色体不分离如何导致唐氏综合征（21 三体）等遗传病。
7. Genetics & Inheritance | 遗传与继承
Mendelian principles include dominance, segregation, and independent assortment. Use Punnett squares to predict genotype and phenotype ratios for monohybrid and dihybrid crosses. Distinguish between autosomal and sex-linked inheritance, such as haemophilia and colour blindness.
孟德尔遗传学原理包括显性、分离和自由组合定律。使用庞纳特方格预测单基因杂交和双基因杂交的基因型与表现型比例。区分常染色体遗传和伴性遗传，如血友病和红绿色盲。
Understand codominance and multiple alleles, as in the ABO blood group system. Pedigree charts are common exam tools; practise determining whether a trait is dominant, recessive, or sex-linked from family histories.
理解共显性与复等位基因，如 ABO 血型系统。系谱图是常见的考题工具；多加练习如何根据家系判断一个性状是显性、隐性还是伴性遗传。
8. Ecology & Energy Flow | 生态学与能量流动
Ecosystems are described by pyramids of number, biomass, and energy. Energy is lost at each trophic level through respiration, heat, and undigested material — typically around 90% loss, limiting food chain length. Learn to construct and analyse pyramid diagrams.
生态系统可通过数量、生物量和能量锥体来描述。能量在每一营养级通过呼吸、散热和未消化物质而损失——通常损失约 90%，这限制了食物链的长度。学会绘制和分析锥体图。
Carbon and nitrogen cycles are essential. In the carbon cycle, processes like photosynthesis, respiration, combustion, and decomposition are key. For nitrogen, focus on nitrogen fixation, nitrification, denitrification, and the role of bacteria such as Rhizobium and Nitrosomonas.
碳循环和氮循环至关重要。碳循环中，光合作用、呼吸作用、燃烧和分解是重点。氮循环关注固氮、硝化、反硝化以及根瘤菌、亚硝化单胞菌等细菌的作用。
9. Human Physiology: Gas Exchange & Circulation | 人体生理：气体交换与循环
The lungs’ alveoli provide a large surface area, thin walls, and a rich blood supply for efficient gas exchange. Ventilation is driven by the diaphragm and intercostal muscles. Be able to trace a molecule of oxygen from the air to a muscle cell.
肺部的肺泡提供了巨大的表面积、薄壁和丰富的血液供应以实现高效的气体交换。肺通气由膈肌和肋间肌驱动。须能追踪一个氧分子从空气到肌肉细胞的路径。
The circulatory system comprises the heart, arteries, veins, and capillaries. Know the cardiac cycle, the roles of sinoatrial node pacemaker, and how blood pressure changes through the circuit. Relate structure of arteries and veins to their function.
循环系统包括心脏、动脉、静脉和毛细血管。掌握心动周期、窦房结起搏点的作用以及血压在循环中的变化。将动脉和静脉的结构与其功能相联系。
10. Plant Biology: Photosynthesis & Transpiration | 植物生物学：光合作用与蒸腾作用
Photosynthesis occurs in chloroplasts and consists of light-dependent reactions (thylakoid membranes) and the Calvin cycle (stroma). The overall equation: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Explain how light intensity, CO₂ concentration, and temperature act as limiting factors.
光合作用在叶绿体中进行，包括光依赖反应（类囊体薄膜）和卡尔文循环（基质）。总方程式为：6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂。解释光照强度、二氧化碳浓度和温度如何成为限制因子。
Transpiration is the loss of water vapour through stomata, driven by the cohesion-tension theory. Water moves from roots to leaves via xylem. Stomatal opening is controlled by guard cells; abscisic acid triggers closure under water stress.
蒸腾作用是通过气孔散失水蒸气，由内聚力-张力理论驱动。水分经木质部从根部运送到叶片。气孔的开闭受保卫细胞调控；脱落酸在水分胁迫下促使其关闭。
11. Evolution & Speciation | 进化与物种形成
Natural selection acts on variation within populations, leading to differential survival and reproduction. Types of selection include stabilising, directional, and disruptive. Speciation occurs when populations become reproductively isolated, either allopatrically or sympatrically.
自然选择作用于种群内的变异，导致差异性生存和繁殖。选择类型包括稳定化选择、定向选择和分裂选择。当种群产生生殖隔离——无论是异域还是同域——物种便形成。
Evidence for evolution includes the fossil record, comparative anatomy, and molecular homologies. Antibiotic resistance in bacteria is a real-time example of natural selection. Both IB and OCR may ask you to analyse graphs showing changing allele frequencies.
进化证据包括化石记录、比较解剖学和分子同源性。细菌的抗生素耐药性是自然选择的实时例证。IB 和 OCR 都可能要求你分析显示等位基因频率变化的图表。
12. Exam Technique & Data Analysis | 考试技巧与数据分析
Read command terms precisely: ‘describe’ means give factual details, ‘explain’ requires reasons or mechanisms, ‘evaluate’ weighs both sides with a conclusion. Plan answers to extended-response questions and always use scientific terminology.
准确解读指令术语：”描述”意味着提供事实细节，”解释”需要给出原因或机制，”评价”则要权衡双方并得出结论。规划好拓展型题目的答案，始终使用科学术语。
For data-based questions, calculate percentage change, means, and standard deviation if required. Spot anomalies and correlation vs causation. When sketching graphs, label axes with units and use sharp pencil lines; best-fit lines are often expected.
处理数据题时，要会计算百分比变化、平均值，必要时的标准差。识别异常值并区分相关与因果。绘制图表时，坐标轴标注单位，使用清晰的铅笔线条；通常要求画出最佳拟合线。
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