📚 GCSE OCR Biology: Last-Minute Revision Notes | GCSE OCR 生物：考前冲刺笔记
Preparing for your OCR GCSE Biology exams? These concise, bilingual notes cover the essential topics from cell biology to global challenges. Each point is explained in English and Chinese so you can reinforce key concepts efficiently.
正在备战 OCR GCSE 生物考试？这份精简的中英双语笔记涵盖了从细胞生物学到全球挑战的核心主题，每个要点均用英文和中文解释，帮助你高效巩固关键概念。
1. Cell Structure | 细胞结构
All living organisms are made of cells. Eukaryotic cells (plants, animals, fungi) have a nucleus, while prokaryotic cells (bacteria) do not. Key organelles include mitochondria for aerobic respiration, ribosomes for protein synthesis, and chloroplasts for photosynthesis in plant cells.
所有生物体都由细胞组成。真核细胞（植物、动物、真菌）有细胞核，而原核细胞（细菌）没有。关键细胞器包括进行有氧呼吸的线粒体、合成蛋白质的核糖体，以及植物细胞中进行光合作用的叶绿体。
Animal cells contain a cell membrane, cytoplasm, and nucleus. Plant cells also have a rigid cell wall, a large permanent vacuole, and chloroplasts.
动物细胞含有细胞膜、细胞质和细胞核。植物细胞还有坚硬的细胞壁、一个大型中央液泡和叶绿体。
The nucleus stores genetic material (DNA) and controls cell activities. The cytoplasm is where most chemical reactions occur.
细胞核储存遗传物质（DNA）并控制细胞活动。细胞质是大多数化学反应发生的场所。
2. Microscopy | 显微镜技术
Light microscopes use lenses to magnify specimens up to about ×2000. Electron microscopes have much higher magnification and resolution, allowing us to see subcellular structures like ribosomes.
光学显微镜使用透镜将标本放大至约2000倍。电子显微镜具有更高的放大倍数和分辨率，使我们能够看到核糖体等亚细胞结构。
To calculate total magnification: multiply the eyepiece lens magnification by the objective lens magnification. Magnification = image size ÷ actual size.
总放大倍数 = 目镜放大倍数 × 物镜放大倍数。放大倍数 = 图像大小 ÷ 实际大小。
When preparing a slide, ensure the specimen is thin, add a drop of water or stain, and lower the coverslip slowly to avoid air bubbles.
制作玻片标本时，确保切片薄，加一滴水或染色剂，并缓慢放下盖玻片以避免气泡。
3. Enzymes | 酶
Enzymes are biological catalysts made of protein. They speed up chemical reactions by lowering the activation energy. Each enzyme has an active site with a specific shape, fitting a complementary substrate — the lock and key model.
酶是由蛋白质构成的生物催化剂。它们通过降低活化能来加速化学反应。每个酶都有一个特定形状的活性位点，与互补底物结合——锁钥模型。
Enzymes are affected by temperature and pH. High temperatures denature the enzyme by breaking bonds, changing the active site shape permanently. Each enzyme has an optimum temperature and pH.
酶受温度和pH的影响。高温会破坏键合使酶变性，永久改变活性位点形状。每种酶都有其最适温度和最适pH。
Denatured enzymes can no longer catalyse reactions because the substrate can no longer fit. The rate of reaction drops sharply beyond the optimum.
变性后的酶无法再催化反应，因为底物不再能契合。超出最适条件后反应速率急剧下降。
4. Respiration | 呼吸作用
Aerobic respiration releases energy from glucose using oxygen. The word equation: glucose + oxygen → carbon dioxide + water (+ energy). It takes place in mitochondria.
有氧呼吸利用氧气从葡萄糖中释放能量。文字方程：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。发生在线粒体中。
Anaerobic respiration in animal cells produces lactic acid without oxygen. In yeast, anaerobic respiration produces ethanol and carbon dioxide (fermentation).
动物细胞中的无氧呼吸在无氧条件下产生乳酸。酵母的无氧呼吸产生乙醇和二氧化碳（发酵）。
Energy from respiration is used for muscle contraction, maintaining body temperature, active transport, and building large molecules like proteins.
呼吸作用释放的能量用于肌肉收缩、维持体温、主动运输以及合成蛋白质等大分子。
5. Photosynthesis | 光合作用
Photosynthesis converts light energy into chemical energy stored in glucose. It occurs in chloroplasts using chlorophyll. Word equation: carbon dioxide + water → glucose + oxygen (in the presence of light).
光合作用将光能转化为储存在葡萄糖中的化学能。它发生在叶绿体中，需要叶绿素。文字方程：二氧化碳 + 水 → 葡萄糖 + 氧气（需要光照）。
Limiting factors include light intensity, carbon dioxide concentration, and temperature. A graph of rate versus factor shows a plateau when another factor becomes limiting.
限制因素包括光照强度、二氧化碳浓度和温度。速率与某因素的关系曲线会因其他因素限制而趋于平缓。
Glucose produced may be used for respiration, converted into starch for storage, turned into cellulose for cell walls, or combined with minerals to make amino acids and oils.
生成的葡萄糖可用于呼吸、转化为淀粉储存、转化为纤维素构建细胞壁，或与矿物质结合制造氨基酸和油脂。
6. DNA and Genetics | DNA 与遗传学
DNA is a double helix polymer made of nucleotides. Each nucleotide contains a sugar, a phosphate group, and a base (A, T, C, G). Complementary base pairing: A pairs with T, C with G.
DNA 是一种双螺旋结构的大分子聚合物，由核苷酸组成。每个核苷酸包含一个糖、一个磷酸基团和一个碱基（A、T、C、G）。碱基互补配对：A与T配对，C与G配对。
A gene is a section of DNA that codes for a specific protein. The sequence of bases determines the order of amino acids in a protein, which gives it a specific shape and function.
基因是编码特定蛋白质的一段DNA。碱基序列决定了蛋白质中氨基酸的顺序，从而赋予蛋白质特定的形状和功能。
Alleles are different versions of the same gene. A dominant allele (e.g., B) only needs one copy to be expressed; a recessive allele (b) requires two copies.
等位基因是同一基因的不同形式。显性等位基因只需一个拷贝就会表达；隐性等位基因需要两个拷贝才能表达。
7. Cell Division | 细胞分裂
Mitosis produces two genetically identical diploid daughter cells, used for growth, repair, and asexual reproduction. The stages: prophase, metaphase, anaphase, telophase (PMAT).
有丝分裂产生两个遗传上相同的二倍体子细胞，用于生长、修复和无性生殖。阶段：前期、中期、后期、末期（PMAT）。
Meiosis produces four genetically different haploid gametes (sperm or egg cells). It involves two divisions, resulting in halving the chromosome number.
减数分裂产生四个遗传上不同的单倍体配子（精子或卵细胞）。包括两次分裂，染色体数目减半。
Stem cells are unspecialised cells that can divide and differentiate into many cell types. Embryonic stem cells can become any type; adult stem cells have limited differentiation potential.
干细胞是未分化的细胞，能够分裂并分化成多种细胞类型。胚胎干细胞可以分化成任何类型；成体干细胞的分化潜力有限。
8. Nervous System and Hormones | 神经系统与激素
The nervous system uses electrical impulses travelling along neurones. A reflex arc goes: stimulus → receptor → sensory neurone → relay neurone (in CNS) → motor neurone → effector → response.
神经系统通过沿神经元传递的电脉冲工作。反射弧路径：刺激 → 感受器 → 感觉神经元 → 中间神经元（中枢神经系统） → 运动神经元 → 效应器 → 反应。
Synapses are gaps between neurones where chemicals (neurotransmitters) diffuse to pass the impulse to the next neurone.
突触是神经元之间的间隙，化学物质（神经递质）在此扩散，将冲动传递到下一个神经元。
Hormones are chemical messengers released into the bloodstream, travelling slowly but with longer-lasting effects. Insulin lowers blood glucose; glucagon raises it — negative feedback maintains homeostasis.
激素是释放到血液中的化学信使，传递速度较慢但作用持久。胰岛素降低血糖；胰高血糖素升高血糖——负反馈维持稳态。
9. Ecology and Cycles | 生态与物质循环
Food chains show energy transfer: producer → primary consumer → secondary consumer → tertiary consumer. Around 90% of energy is lost at each trophic level, mainly through heat and respiration.
食物链显示能量传递：生产者 → 初级消费者 → 次级消费者 → 三级消费者。每个营养级大约90%的能量会以热和呼吸作用等形式散失。
The carbon cycle: carbon dioxide is removed from the atmosphere by photosynthesis, and returned by respiration, combustion of fossil fuels, and decomposition. Microorganisms decay organic matter.
碳循环：光合作用将二氧化碳从大气中移除，呼吸作用、化石燃料燃烧和分解作用将其返还。微生物分解有机物。
The water cycle involves evaporation, transpiration from plants, condensation to form clouds, and precipitation. Water then runs off or infiltrates into groundwater.
水循环包括蒸发、植物蒸腾作用、凝结形成云和降水。之后水形成径流或渗入地下水。
10. Circulatory System | 循环系统
The human heart is a double pump. The right side pumps deoxygenated blood to the lungs; the left side pumps oxygenated blood to the body. Valves prevent backflow.
人类心脏是一个双重泵。右心将缺氧血泵至肺部；左心将富氧血泵至全身。瓣膜防止血液倒流。
Arteries carry blood away from the heart under high pressure; veins return blood under low pressure and have valves. Capillaries are one-cell thick for efficient diffusion.
动脉将血液从心脏高压输出；静脉将血液低压送回，并具有瓣膜。毛细血管仅一个细胞厚，便于高效扩散。
Blood contains red blood cells (transport oxygen, no nucleus, contain haemoglobin), white blood cells (defend against pathogens), platelets (clotting), and plasma (transports dissolved substances).
血液包含红细胞（运输氧，无细胞核，含血红蛋白）、白细胞（抵御病原体）、血小板（凝血）和血浆（运输溶解物质）。
11. Disease and Immunity | 疾病与免疫
Pathogens include bacteria, viruses, fungi, and protists. They can spread through air, direct contact, water, or vectors. The body’s first line of defence includes skin, mucus, and stomach acid.
病原体包括细菌、病毒、真菌和原生生物。它们可通过空气、直接接触、水或媒介传播。身体的第一道防线包括皮肤、黏液和胃酸。
White blood cells engulf pathogens (phagocytosis), produce antibodies that bind to specific antigens, and produce antitoxins. Memory cells remain for long-term immunity.
白细胞通过吞噬作用吞噬病原体，产生与特定抗原结合的抗体，并产生抗毒素。记忆细胞存留以提供长期免疫。
Vaccination introduces a dead or weakened pathogen to stimulate antibody production and memory cell formation, without causing illness. Herd immunity protects unvaccinated individuals.
疫苗接种引入灭活或减毒的病原体，刺激抗体产生和记忆细胞形成，而不致病。群体免疫可保护未接种者。
12. Evolution and Natural Selection | 进化与自然选择
Natural selection occurs when individuals with advantageous alleles are more likely to survive and reproduce, passing on those alleles. Over generations, the frequency of these alleles increases.
拥有有利等位基因的个体更有可能生存和繁殖，并将这些等位基因传递下去，这就是自然选择。经过若干代后，这些等位基因的频率增加。
Darwin’s finches on the Galápagos Islands show adaptation: beak shapes evolved to suit different food sources. The theory of evolution by natural selection is supported by fossil records and DNA evidence.
加拉帕戈斯群岛的达尔文雀展示了适应性：喙的形状进化以适应不同食物来源。化石记录和DNA证据支持自然选择进化论。
Antibiotic-resistant bacteria evolve when a mutation gives some bacteria survival advantage; antibiotic use kills non‑resistant strains, leaving resistant ones to multiply — a clear example of natural selection.
耐药性细菌的进化：当突变赋予某些细菌生存优势后，使用抗生素会杀死非耐药菌株，留下耐药菌繁殖——这是自然选择的典型例子。
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