📚 Year 11 OCR Biology: Key Concepts Revision | Year 11 OCR 生物：核心知识点梳理
This guide brings together the core topics from the Year 11 OCR GCSE Biology specification, covering cell biology, organisation, infection and response, bioenergetics, homeostasis, genetics and ecology. Each section presents key facts, definitions and processes in paired English–Chinese paragraphs to support bilingual revision.
本指南汇总了 Year 11 OCR GCSE 生物大纲的核心主题，涵盖细胞生物学、组织结构、感染与免疫、生物能学、稳态、遗传学和生态学。每个小节以中英配对段落呈现关键事实、定义和过程，助力双语复习。
1. Cell Structure and Transport | 细胞结构与运输
All living things are made of cells. The two main categories are prokaryotic cells (bacteria) which lack a nucleus, and eukaryotic cells (animal, plant, fungi) which have a true nucleus and membrane-bound organelles.
所有生物都由细胞组成。两大类细胞分别是原核细胞（细菌），没有细胞核，以及真核细胞（动物、植物、真菌），具有真正的细胞核和膜包被的细胞器。
Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells have these plus a permanent vacuole, chloroplasts and a rigid cell wall made of cellulose.
动物细胞含有细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞除此之外还有中央大液泡、叶绿体和由纤维素构成的坚硬细胞壁。
Specialised cells, such as sperm cells (flagellum, many mitochondria), nerve cells (long axon) and root hair cells (large surface area), are adapted to carry out specific functions.
特化的细胞，如精细胞（有鞭毛、大量线粒体）、神经细胞（长轴突）和根毛细胞（大表面积），都适应其特定的功能。
Substances move across cell membranes by diffusion (net movement of particles from high to low concentration), osmosis (diffusion of water through a partially permeable membrane) and active transport (movement against a concentration gradient, requiring energy from respiration).
物质通过扩散（粒子净移动从高浓度到低浓度）、渗透（水通过部分透性膜的扩散）和主动运输（逆浓度梯度移动，需要呼吸作用提供的能量）穿过细胞膜。
2. Cell Division | 细胞分裂
The nucleus contains chromosomes made of DNA. Each chromosome carries many genes. Body cells have two sets of chromosomes (diploid), while gametes have one set (haploid).
细胞核含有由 DNA 构成的染色体。每条染色体携带许多基因。体细胞有两套染色体（二倍体），配子有一套染色体（单倍体）。
The cell cycle includes cell growth, DNA replication, then mitosis (nucleus division) and cytokinesis. Mitosis produces two genetically identical daughter cells and is used for growth, repair and asexual reproduction.
细胞周期包括细胞生长、DNA 复制，然后是有丝分裂（细胞核分裂）和胞质分裂。有丝分裂产生两个遗传上相同的子细胞，用于生长、修复和无性繁殖。
Stem cells are unspecialised cells that can differentiate into different cell types. Embryonic stem cells can become any cell type, while adult stem cells (e.g. in bone marrow) can form only certain types. Stem cells are used in medicine to replace damaged tissues, but their use raises ethical concerns.
干细胞是尚未特化的细胞，能分化成不同细胞类型。胚胎干细胞可以变成任何细胞类型，而成体干细胞（如骨髓中的）只能形成某些类型。干细胞在医学上用于替换受损组织，但使用它们也引发了伦理问题。
When the cell cycle becomes uncontrolled, a tumour can form. Benign tumours grow slowly and do not invade, whereas malignant tumours are cancerous and can spread to other parts of the body, forming secondary tumours.
当细胞周期失控时，会形成肿瘤。良性肿瘤生长缓慢且不侵入周围组织，而恶性肿瘤是癌性的，能扩散到身体其他部位，形成继发肿瘤。
3. Organisation and Digestion | 组织与消化
le cells form muscle tissue, which makes up the stomach, an organ of the digestive system.
大型多细胞生物以 细胞 → 组织 → 器官 → 器官系统 的层次组织。例如，肌肉细胞构成肌肉组织，肌肉组织构成胃，胃是消化系统的一个器官。
The digestive system breaks down food into small soluble molecules that can be absorbed into the blood. Key organs include the mouth, oesophagus, stomach, small intestine (with villi for absorption), pancreas and large intestine.
消化系统将食物分解成可溶于水的小分子以便吸收进入血液。关键器官包括口腔、食道、胃、小肠（有绒毛负责吸收）、胰腺和大肠。
Enzymes are biological catalysts made of protein. The 'lock and key' model explains enzyme specificity. Carbohydrases (e.g. amylase) break down starch into sugars, proteases break proteins into amino acids, and lipases break lipids into fatty acids and glycerol. Bile, produced by the liver and stored in the gall bladder, emulsifies fats and neutralises stomach acid.
酶是由蛋白质构成的生物催化剂。“锁钥”模型解释了酶的专一性。碳水化合物酶（如淀粉酶）将淀粉分解成糖，蛋白酶将蛋白质分解成氨基酸，脂肪酶将脂肪分解成脂肪酸和甘油。胆汁由肝脏产生、储存在胆囊中，能乳化脂肪并中和胃酸。
The required practicals for this topic include food tests (iodine for starch, Biuret for protein, Benedict's for reducing sugars, ethanol emulsion for fats) and investigating the effect of pH or temperature on enzyme activity.
该主题的必做实验包括食物测试（碘液检测淀粉、双缩脲检测蛋白质、本尼迪克特试剂检测还原糖、乙醇乳液检测脂肪），以及探究 pH 或温度对酶活性的影响。
4. The Circulatory System and Plant Transport | 循环系统与植物运输
The human circulatory system consists of the heart, blood vessels and blood. It is a double circulatory system: the right side pumps blood to the lungs, the left side pumps oxygenated blood to the body.
人体循环系统由心脏、血管和血液组成。它是双循环系统：右心室将血泵入肺部，左心室将富氧血泵至全身。
The heart has four chambers (right and left atria, right and left ventricles) and valves to prevent backflow. Coronary arteries supply the heart muscle with oxygen. Blockage of these arteries can lead to coronary heart disease, treated with stents, statins or bypass surgery.
心脏有四个腔室（左右心房、左右心室）和防止回流的瓣膜。冠状动脉为心肌供氧。冠状动脉堵塞可导致冠心病，治疗方式有支架、他汀类药物或搭桥手术。
Blood contains red blood cells (carry oxygen using haemoglobin), white blood cells (immune defence), platelets (clotting) and plasma (transports dissolved substances, hormones and waste).
血液含有红细胞（用血红蛋白携带氧气）、白细胞（免疫防御）、血小板（凝血）和血浆（运输溶解的物质、激素和废物）。
In plants, xylem vessels transport water and dissolved minerals from roots to shoots – the transpiration stream is driven by evaporation from leaves. Phloem tubes transport dissolved sugars (translocation). Transpiration rate is affected by light intensity, temperature, air movement and humidity.
植物中，木质部导管将水分和溶解的矿物质从根部向上运输——蒸腾流是由叶片蒸发驱动的。韧皮部管负责运输溶解的糖（转运）。蒸腾速率受光照强度、温度、空气流动和湿度的影响。
5. Infectious Diseases and Immune Response | 传染病与免疫反应
Infectious diseases are caused by pathogens: viruses (e.g. measles, HIV, tobacco mosaic virus), bacteria (e.g. Salmonella, gonorrhoea), fungi (e.g. rose black spot) and protists (e.g. malaria). Pathogens can be spread through air, water, direct contact or vectors.
传染病由病原体引起：病毒（如麻疹、HIV、烟草花叶病毒）、细菌（如沙门氏菌、淋病）、真菌（如玫瑰黑斑病）和原生生物（如疟疾）。病原体可通过空气、水、直接接触或媒介生物传播。
Viral diseases: measles causes fever and a rash, and is spread by droplet infection. HIV attacks immune cells and can lead to AIDS. Tobacco mosaic virus (TMV) causes a mosaic pattern on leaves, reducing photosynthesis.
病毒性疾病：麻疹引起发热和皮疹，通过飞沫传播。HIV 攻击免疫细胞，可导致艾滋病。烟草花叶病毒使叶片出现花斑，降低光合作用。
Bacterial diseases: Salmonella (food poisoning) causes diarrhoea and fever, spread through undercooked food. Gonorrhoea is a sexually transmitted infection causing discharge and pain. Rose black spot is a fungal disease that damages leaves; it is spread in the wind or by water.
细菌性疾病：沙门氏菌引起食物中毒，导致腹泻和发热，通过未煮熟的食物传播。淋病是一种性传播感染，引起分泌物和疼痛。玫瑰黑斑病是真菌病害，损害叶片，通过风和水传播。
Malaria is caused by a protist parasite, carried by mosquitoes. It causes recurrent fevers and can be controlled by using mosquito nets and antimalarial drugs.
疟疾由一种原生寄生虫引起，由蚊子传播。它导致反复发热，可通过使用蚊帐和抗疟药物进行控制。
The immune system defends the body through white blood cells: phagocytes engulf and digest pathogens (phagocytosis); lymphocytes produce specific antibodies that bind to antigens, and antitoxins that neutralise toxins.
免疫系统通过白细胞保卫身体：吞噬细胞吞噬并消化病原体（吞噬作用）；淋巴细胞产生特异性抗体与抗原结合，并产生抗毒素中和毒素。
Vaccination introduces a harmless form of a pathogen's antigen, stimulating lymphocytes to produce memory cells. This allows a faster, stronger secondary response upon later exposure, providing immunity. Vaccination has eradicated smallpox and reduced diseases like polio and measles.
疫苗接种引入无害的病原体抗原形式，刺激淋巴细胞产生记忆细胞。这使得日后再次接触时能发生更快、更强的二次应答，提供免疫力。疫苗已消灭天花，并减少了脊髓灰质炎和麻疹等疾病。
6. Preventing and Treating Disease | 疾病的预防与治疗
Antibiotics, such as penicillin, kill bacteria or stop them reproducing. They do not work against viruses, because viruses live inside host cells. Painkillers only relieve symptoms but do not kill pathogens.
抗生素，如青霉素，能杀死细菌或阻止其繁殖。它们对病毒无效，因为病毒生活在宿主细胞内。止痛药只能缓解症状，而不能杀死病原体。
Antibiotic resistance arises when bacteria mutate. Those with resistant genes survive and reproduce, spreading resistance. MRSA is an example. To slow resistance, doctors should avoid unnecessary prescriptions and patients should complete the full course.
当细菌发生突变时，就会出现抗生素耐药性。那些具有耐药基因的细菌存活并繁殖，传播耐药性。MRSA 就是一个例子。为了减缓耐药性，医生应避免不必要的处方，患者应完成整个疗程。
Many drugs were originally discovered from plants and microorganisms. Digoxin comes from foxgloves; aspirin is from willow bark; penicillin was discovered by Alexander Fleming from the Penicillium mould. New drugs are tested for toxicity, efficacy and dose in preclinical (cells, animals) and clinical trials (healthy volunteers, then patients), often using double-blind placebo designs.
许多药物最初是从植物和微生物中发现的。地高辛来自毛地黄；阿司匹林来自柳树皮；青霉素由亚历山大·弗莱明从青霉菌中发现。新药需进行毒性、疗效和剂量测试，包括临床前试验（细胞、动物）和临床试验（健康志愿者，然后是患者），常采用双盲安慰剂设计。
Monoclonal antibodies are identical antibodies produced from a single clone of hybridoma cells. They bind to a specific antigen and are used in pregnancy tests, diagnosis (e.g. for cancer markers) and targeted therapy to deliver drugs or radioactive substances directly to cancer cells.
单克隆抗体是由单一杂交瘤细胞克隆产生的完全相同的抗体。它们与特定抗原结合，用于验孕、诊断（如癌症标记物）和靶向治疗，将药物或放射性物质直接递送至癌细胞。
7. Photosynthesis | 光合作用
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Photosynthesis is an endothermic reaction in which chloroplasts use light energy to convert carbon dioxide and water into glucose and oxygen. The glucose is used for respiration, stored as starch, converted to cellulose for cell walls, combined with nitrate ions to make amino acids and proteins, or turned into lipids for storage.
光合作用是一个吸热反应，叶绿体利用光能将二氧化碳和水转化为葡萄糖和氧气。葡萄糖用于呼吸作用，储存为淀粉，转化为纤维素构成细胞壁，与硝酸根离子结合制造氨基酸和蛋白质，或转化为脂质储存。
The rate of photosynthesis is affected by light intensity, carbon dioxide concentration, temperature and the amount of chlorophyll. A limiting factor is the one that is in shortest supply and restricts the rate. Graphs show the rate levels off as a factor becomes limiting.
光合作用速率受光照强度、二氧化碳浓度、温度和叶绿素含量的影响。限制因子是供应最短缺并限制速率的那一个。图表显示，当某一因子成为限制时，速率会趋于稳定。
In the required practical, pondweed (e.g. Elodea) is placed in water with a light source. The rate of photosynthesis is measured by counting oxygen bubbles produced per minute, while changing light distance or adding sodium hydrogencarbonate (CO₂ source). It is important to control temperature and give time for the plant to adjust.
在必做实验中，将水草（如伊乐藻）放在水中并设置光源。通过计数每分钟产生的氧气气泡来测量光合速率，同时改变灯距或加入碳酸氢钠（二氧化碳源）。重要的是控制温度，并给植物时间适应。
8. Respiration | 呼吸作用
Aerobic: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (+ ATP)
Respiration is an exothermic reaction that releases energy from glucose for metabolic processes. Aerobic respiration uses oxygen and produces a large amount of energy. It takes place continuously in the mitochondria of cells.
呼吸作用是一个放热反应，从葡萄糖中释放能量供代谢过程使用。有氧呼吸需要氧气，产生大量能量。它在细胞的线粒体中持续进行。
Anaerobic (animal): Glucose → Lactic acid (+ small ATP)
Anaerobic (plant/yeast): Glucose → Ethanol + CO₂ (+ small ATP)
When oxygen is insufficient, anaerobic respiration occurs. In animal cells, glucose is converted to lactic acid, causing muscle fatigue and an oxygen debt that is repaid by breathing deeply afterwards. In plants and yeast, anaerobic respiration produces ethanol and carbon dioxide (fermentation).
当氧气不足时，就会发生无氧呼吸。在动物细胞中，葡萄糖被转化为乳酸，导致肌肉疲劳和氧债，事后需要通过深呼吸偿还。在植物和酵母中，无氧呼吸产生乙醇和二氧化碳（发酵）。
Metabolism refers to the sum of all chemical reactions in an organism. The energy from respiration drives the synthesis of new molecules, including proteins from amino acids, glycogen from glucose in muscles and liver, and lipid storage. It also maintains body temperature and enables muscle contraction.
代谢指生物体内所有化学反应的总和。呼吸作用释放的能量驱动新分子的合成，包括由氨基酸合成蛋白质、在肌肉和肝脏中由葡萄糖合成糖原，以及脂质储存。它还维持体温并促使肌肉收缩。
9. The Nervous System and Homeostasis | 神经系统与稳态
The nervous system uses electrical impulses to bring about rapid, precise responses. A reflex arc involves a receptor, sensory neurone, relay neurone (in the CNS), motor neurone and effector (muscle or gland). Synapses use chemicals (neurotransmitters) to pass impulses between neurones.
神经系统利用电冲动实现快速、精确的反应。反射弧包括感受器、感觉神经元、中间神经元（在中枢神经系统内）、运动神经元和效应器（肌肉或腺体）。突触通过化学物质（神经递质）在神经元之间传递冲动。
The brain controls complex behaviour and consists of the cerebral cortex (conscious thought, memory), cerebellum (coordination and balance) and medulla (unconscious activities like breathing). Brain damage can be studied with MRI scans, but treating brain disorders is difficult due to the complexity and risk of further damage.
大脑控制复杂行为，由大脑皮层（有意识的思维、记忆）、小脑（协调与平衡）和延髓（非意识活动如呼吸）组成。脑损伤可通过 MRI 扫描研究，但由于其复杂性和进一步损伤的风险，治疗脑部疾病很困难。
The eye is a sensory organ. Light enters through the cornea, passes through the pupil (controlled by the iris), is focused by the lens and forms an image on the retina. Accommodation is the lens changing shape to focus on near or distant objects. Defects include myopia (short-sightedness) corrected with concave lenses, and hyperopia (long-sightedness) corrected with convex lenses.
眼睛是一个感觉器官。光线通过角膜进入，穿过瞳孔（由虹膜控制），经晶状体聚焦，在视网膜上形成图像。调节是指晶状体改变形状以聚焦远近物体。缺陷包括近视（用凹透镜矫正）和远视（用凸透镜矫正）。
Homeostasis is the maintenance of a constant internal environment. Key examples include body temperature regulation (thermoregulation through sweating, shivering, vasodilation and vasoconstriction) and blood water and ion balance (controlled by the kidneys and ADH hormone).
稳态是维持恒定内环境的过程。重要例子包括体温调节（通过出汗、颤抖、血管舒张和血管收缩进行温度调节）以及血液水分和离子平衡（由肾脏和抗利尿激素 ADH 控制）。
10. Hormones and Reproduction | 激素与生殖
Hormones are chemical messengers produced by endocrine glands, carried in the blood to target organs. Compared to the nervous system, hormonal responses are slower but longer lasting. The pituitary gland is the 'master gland', secreting many hormones that regulate other glands.
激素是由内分泌腺产生的化学信使，经血液运送到靶器官。与神经系统相比，激素反应较慢，但持续时间较长。垂体是“主腺体”，分泌多种调节其他腺体的激素。
Blood glucose concentration is controlled by insulin (from pancreas) which lowers glucose by converting it to glycogen in the liver and muscles, and glucagon which raises glucose by converting glycogen back to glucose. Type 1 diabetes is when the pancreas produces little or no insulin (treated with insulin injections). Type 2 diabetes is when body cells become resistant to insulin, often linked to obesity and poor diet.
血糖浓度由胰岛素（来自胰腺）控制，它通过将葡萄糖在肝脏和肌肉中转化为糖原来降低血糖；胰高血糖素则通过将糖原转化回葡萄糖来升高血糖。1 型糖尿病是胰腺几乎不产胰岛素（用胰岛素注射治疗）。2 型糖尿病是身体细胞对胰岛素产生抵抗，常与肥胖和不良饮食有关。
In human reproduction, hormones control the menstrual cycle. FSH (from pituitary) stimulates egg maturation and oestrogen production. Oestrogen (from ovaries) thickens the uterus lining and triggers a surge of LH. LH (from pituitary) stimulates ovulation. Progesterone (from the corpus luteum) maintains the lining. If fertilisation does not occur, progesterone levels drop and menstruation happens.
在人类生殖中，激素控制月经周期。促卵泡激素 FSH（垂体）刺激卵子成熟和雌激素产生。雌激素（卵巢）使子宫内膜增厚并引发促黄体生成素 LH 的激增。LH（垂体）刺激排卵。孕酮（由黄体分泌）维持内膜。如果没有受精，孕酮水平下降，月经来潮。
Contraceptive pills (oral contraceptives) often contain oestrogen and progesterone to inhibit FSH and prevent ovulation. Fertility treatments may involve giving FSH and LH to stimulate ovulation (IVF). Plant hormones (auxins) control phototropism and gravitropism; synthetic auxins are used as weedkillers and rooting powders.
避孕药通常含有雌激素和孕酮，抑制 FSH 从而阻止排卵。生育治疗可能涉及给予 FSH 和 LH 刺激排卵（体外受精 IVF）。植物激素（生长素）控制向光性和向地性；人工合成的生长素用作除草剂和生根粉。
11. Genetics and Evolution | 遗传与进化
DNA is a double helix polymer containing four bases: adenine (A), thymine (T), cytosine (C) and guanine (G). A gene is a section of DNA that codes for a particular protein. Different forms of a gene are called alleles. The genome is the entire genetic material of an organism.
DNA 是双螺旋聚合物，包含四种碱基：腺嘌呤 (A)、胸腺嘧啶 (T)、胞嘧啶 (C) 和鸟嘌呤 (G)。基因是编码特定蛋白质的一段 DNA。基因的不同形式称为等位基因。基因组是生物体的全部遗传物质。
In monohybrid inheritance, Punnett squares predict the probability of offspring genotypes. A dominant allele is always expressed even if only one copy is present. A recessive allele is expressed only if two copies are present. Homozygous means two identical alleles, heterozygous means two different alleles.
在单基因遗传中，庞尼特方格可预测子代基因型的概率。显性等位基因只要存在一个副本就会表达。隐性等位基因只有在两个副本都存在时才表达。纯合指两个等位基因相同，杂合指两个等位基因不同。
Inherited disorders: Polydactyly (extra digits) is caused by a dominant allele. Cystic fibrosis (thick sticky mucus affecting lungs and digestive system) is caused by a recessive allele; carriers have one normal and one faulty allele without showing symptoms.
遗传病：多指症由显性等位基因引起。囊性纤维化（浓稠黏液影响肺和消化系统）由隐性等位基因引起；携带者有一个正常和一个缺陷等位基因而不表现症状。
Evolution by natural selection: variation within a population, some have advantageous characteristics. Those best adapted survive and reproduce more, passing on beneficial alleles to offspring. Over generations, the advantageous trait becomes more common. Antibiotic resistance in bacteria is a clear example.
自然选择进化：种群内存在变异，部分个体具有有利特征。适应能力最强的个体存活并繁殖更多，将有利等位基因传递给后代。经过多代，有利性状变得更普遍。细菌的抗生素耐药性便是一个清晰的例子。
Genetic engineering: genes from one organism are inserted into another. For example, the human insulin gene is placed into bacteria to produce insulin for diabetics. GM crops have been developed for higher yield or resistance to pests. Cloning produces genetically identical individuals; plants can be cloned by tissue culture or cuttings, animals by embryo splitting or somatic cell nuclear transfer.
基因工程：将一个生物的基因插入另一生物。例如，将人胰岛素基因放入细菌中以生产供糖尿病患者使用的胰岛素。转基因作物已被培育以获得更高产量或抗虫性。克隆产生遗传相同的个体；植物可通过组织培养或扦插克隆，动物可通过胚胎分裂或体细胞核移植克隆。
12. Ecology and Material Cycles | 生态与物质循环
Ecosystems consist of communities of living organisms interacting with their abiotic environment. Interdependence means organisms depend on each other for food, shelter, pollination and seed dispersal. A stable community shows little change in population sizes.
生态系统由生物群落及其与非生物环境相互作用组成。相互依存意味着生物在食物、庇护所、传粉和种子传播等方面互相依赖。一个稳定的群落中，种群大小变化很小。
Organisms compete
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