📚 Core Topics for Year 11 CAIE Biology | Year 11 CAIE 生物核心知识点梳理
Year 11 CAIE Biology builds on fundamental concepts to prepare students for the IGCSE examinations. This article distils the essential topics, focusing on key definitions, processes, and connections that frequently appear in Paper 2, 4 and 6. Understanding these core areas deeply will not only help you tackle structured and multiple-choice questions with confidence but also form a solid foundation for future A-Level study.
Year 11 CAIE 生物在基础概念上进一步深化，为 IGCSE 考试做好准备。本文精炼了核心专题，聚焦于频繁出现在卷二、卷四和卷六中的关键定义、过程和联系。深入理解这些核心领域，不仅能让你自信应对简答题和选择题，也为未来的 A-Level 学习打下坚实基础。
1. Cell Structure and Function | 细胞结构与功能
All living organisms are made of cells. Animal cells contain a nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells additionally have a cell wall, chloroplasts and a large permanent vacuole. The nucleus controls cell activities and contains genetic material (DNA). Mitochondria are the site of aerobic respiration, releasing energy. Ribosomes carry out protein synthesis.
所有生物都由细胞构成。动物细胞含有细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞还额外具有细胞壁、叶绿体和一个大液泡。细胞核控制细胞活动并含有遗传物质（DNA）。线粒体是有氧呼吸的场所，释放能量。核糖体进行蛋白质合成。
Specialised cells are adapted to perform specific functions. For example, red blood cells have no nucleus and are biconcave to maximise oxygen transport. Root hair cells have a long extension to increase surface area for water and mineral uptake. Ciliated cells move mucus along the respiratory tract.
特化细胞适应执行特定功能。例如，红细胞无核且呈双凹圆盘状，以最大化氧气运输。根毛细胞有长突起以增加吸收水分和矿物质的表面积。纤毛细胞沿着呼吸道移动粘液。
2. Movement Across Membranes | 膜运输
Substances move across cell membranes by diffusion, osmosis and active transport. Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration down a concentration gradient; it is passive and does not require energy. Osmosis is the diffusion of water molecules through a partially permeable membrane from a dilute solution to a more concentrated one.
物质通过扩散、渗透和主动运输穿过细胞膜。扩散是粒子从高浓度区域向低浓度区域的净移动，顺浓度梯度；它是被动的，不需要能量。渗透是水分子通过半透膜从稀溶液向较浓溶液的扩散。
Active transport moves substances against a concentration gradient, from low to high concentration, using energy from respiration in the form of ATP. Carrier proteins in the membrane are involved. This process is vital for mineral ion uptake in root hairs and glucose absorption in kidney tubules.
主动运输逆浓度梯度移动物质，从低浓度到高浓度，使用呼吸作用释放的能量（ATP）。涉及膜中的载体蛋白。该过程对根毛吸收矿物质离子和肾小管中葡萄糖的重吸收至关重要。
3. Biological Molecules | 生物分子
Carbohydrates, proteins and lipids are the main groups of biological molecules. Carbohydrates include simple sugars like glucose (C₆H₁₂O₆) and complex polysaccharides such as starch, glycogen and cellulose. Starch and glycogen serve as energy stores; cellulose gives strength to plant cell walls. Proteins are made of amino acids linked by peptide bonds, and lipids consist of fatty acids and glycerol.
糖类、蛋白质和脂质是主要的生物分子类别。糖类包括葡萄糖（C₆H₁₂O₆）等单糖，以及复杂的多糖如淀粉、糖原和纤维素。淀粉和糖原作为能量储存；纤维素赋予植物细胞壁强度。蛋白质由氨基酸通过肽键连接而成，脂质则由脂肪酸和甘油组成。
The Benedict’s test is used to detect reducing sugars (blue to brick-red upon heating). Iodine solution tests for starch (turns blue-black). The biuret test identifies proteins (turns purple), and the emulsion test is used for lipids (white cloudy layer).
本尼迪克特试剂用于检测还原糖（加热后由蓝色变成砖红色）。碘液测试淀粉（变成蓝黑色）。双缩脲试验鉴定蛋白质（变成紫色），乳剂试验用于脂质测定（出现白色浑浊层）。
4. Enzymes | 酶
Enzymes are biological catalysts made of protein. They speed up chemical reactions by lowering the activation energy, without being used up. Each enzyme has an active site with a specific shape that fits its substrate – the lock-and-key model. Enzyme activity is affected by temperature and pH; they have an optimum temperature (around 37 °C in humans) and an optimum pH (e.g. pH 2 for pepsin, pH 7–8 for salivary amylase).
酶是由蛋白质制成的生物催化剂。它们通过降低活化能来加速化学反应，自身不被消耗。每种酶都有一个活性位点，形状与底物互补——锁钥模型。酶活性受温度和 pH 的影响；它们有最适温度（人体中约 37 °C）和最适 pH（如胃蛋白酶 pH 2，唾液淀粉酶 pH 7–8）。
High temperatures or extreme pH denature enzymes, changing the shape of the active site permanently so the substrate no longer fits. Low temperature only slows enzyme action without denaturation. Enzymes are essential in digestion, respiration and DNA replication.
高温或极端 pH 会使酶变性，永久改变活性位点形状，底物不再结合。低温只是减慢酶的作用而不使其变性。酶在消化、呼吸和 DNA 复制中至关重要。
5. Plant Nutrition and Photosynthesis | 植物营养和光合作用
verall word equation is: carbon dioxide + water → glucose + oxygen. The balanced chemical equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. Chloroplasts contain chlorophyll in the thylakoid membranes where the light-dependent reactions occur.
光合作用是植物利用叶绿素捕获的光能，将二氧化碳和水转化为葡萄糖的过程。总的文字方程式为：二氧化碳 + 水 → 葡萄糖 + 氧气。平衡化学方程式为：6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂。叶绿体在类囊体膜上含有叶绿素，光依赖反应在此进行。
Limiting factors for photosynthesis include light intensity, carbon dioxide concentration and temperature. The glucose produced is used for respiration, stored as starch or converted into cellulose, proteins and lipids for growth. Nitrate ions are needed for amino acid synthesis; magnesium ions are required to make chlorophyll.
光合作用的限制因素包括光照强度、二氧化碳浓度和温度。产生的葡萄糖用于呼吸作用，以淀粉形式储存，或转化为纤维素、蛋白质和脂质用于生长。硝酸根离子是合成氨基酸所必需的；镁离子用于制造叶绿素。
6. Animal Nutrition and Digestion | 动物营养和消化
Animals need a balanced diet containing carbohydrates, proteins, lipids, vitamins, minerals, water and dietary fibre. The human digestive system consists of the mouth, oesophagus, stomach, small intestine (duodenum and ileum), large intestine, rectum and anus. Accessory organs include salivary glands, liver, gall bladder and pancreas.
动物需要包含糖类、蛋白质、脂质、维生素、矿物质、水和膳食纤维的均衡饮食。人体消化系统包括口腔、食道、胃、小肠（十二指肠和回肠）、大肠、直肠和肛门。附属器官包括唾液腺、肝脏、胆囊和胰腺。
Digestion involves physical breakdown (chewing, churning) and chemical digestion by enzymes. Amylase breaks down starch into maltose. Proteases break proteins into amino acids. Lipase digests lipids into fatty acids and glycerol. Bile (produced by the liver, stored in the gall bladder) emulsifies fats and neutralises stomach acid. Absorption of digested food mainly occurs in the ileum where villi provide a large surface area.
消化涉及物理性分解（咀嚼、搅拌）和化学性消化酶作用。淀粉酶将淀粉分解为麦芽糖。蛋白酶将蛋白质分解为氨基酸。脂肪酶将脂质消化为脂肪酸和甘油。胆汁（肝脏分泌，胆囊储存）乳化脂肪并中和胃酸。消化产物的吸收主要发生在回肠，绒毛提供了巨大的表面积。
7. Transport in Plants | 植物运输
Xylem and phloem are the two transport tissues in flowering plants. Xylem vessels transport water and dissolved minerals from roots to the leaves. The movement is driven by transpiration pull (cohesion-tension theory). Xylem cells are dead, hollow tubes strengthened with lignin. Phloem transports sugars (mainly sucrose) and amino acids from sources to sinks; this is called translocation. Phloem is made of living sieve tube elements and companion cells.
木质部和韧皮部是开花植物的两种运输组织。木质部导管将水和溶解的矿物质从根运输到叶。运动由蒸腾拉力驱动（内聚力-张力理论）。木质部细胞是死细胞，空管，由木质素增强。韧皮部将糖（主要是蔗糖）和氨基酸从源运输到库，这称为运输作用。韧皮部由活的筛管分子和伴胞构成。
Factors affecting transpiration rate include light intensity, temperature, humidity and wind speed. Increased light opens stomata, leading to more water loss. High temperature increases evaporation; humidity reduces the concentration gradient; wind removes water vapour speeding up transpiration.
影响蒸腾速率的因素包括光照强度、温度、湿度和风速。光照增强气孔张开，导致更多水分流失。高温增加蒸发；高湿度减小浓度梯度；风吹走水蒸气加快蒸腾。
8. Transport in Animals | 动物运输
has four chambers: right atrium, right ventricle, left atrium and left ventricle. The left ventricle has a thicker muscular wall because it pumps blood at high pressure to the whole body. Valves prevent backflow of blood.
哺乳动物有双循环系统：肺循环（心脏→肺→心脏）和体循环（心脏→身体→心脏）。心脏有四个腔：右心房、右心室、左心房和左心室。左心室壁肌肉较厚，因为它必须以高压泵送血液到全身。瓣膜防止血液倒流。
Arteries carry blood away from the heart under high pressure; they have thick muscular and elastic walls. Veins return blood at lower pressure; they contain valves. Capillaries are one-cell thick for efficient exchange of substances. Blood consists of plasma, red blood cells, white blood cells and platelets. Red blood cells contain haemoglobin, which binds oxygen in the lungs and releases it in tissues.
动脉将血液从心脏高压运出；它们具有厚实的肌肉和弹性壁。静脉在较低压下将血液送回；它们含有瓣膜。毛细血管仅有一层细胞厚，利于高效的物质交换。血液由血浆、红细胞、白细胞和血小板组成。红细胞含有血红蛋白，在肺部结合氧，在组织中释放氧。
9. Respiration | 呼吸作用
carbon dioxide + water (+ energy). The balanced equation is C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. Anaerobic respiration occurs when oxygen is insufficient. In yeast, it produces ethanol and carbon dioxide (fermentation). In muscles, it produces lactic acid and a small amount of energy.
呼吸作用是释放葡萄糖中能量的化学过程。有氧呼吸利用氧气完全氧化葡萄糖：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。平衡方程式为 C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O。无氧呼吸在缺氧时发生。在酵母中，产生乙醇和二氧化碳（发酵作用）。在肌肉中，产生乳酸和少量能量。
Aerobic respiration yields approximately 36–38 ATP molecules per glucose, while anaerobic yields only 2 ATP. The respiration rate can be measured by oxygen uptake or carbon dioxide release. Breathing (ventilation) is distinct: it supplies oxygen and removes carbon dioxide.
有氧呼吸每分子葡萄糖产生约 36–38 个 ATP，而无氧呼吸仅产生 2 个 ATP。呼吸速率可通过氧气消耗或二氧化碳释放量来测量。呼吸运动（换气）是有区别的：它提供氧气并排出二氧化碳。
10. Coordination and Response | 协调与反应
The nervous system allows rapid communication. A stimulus triggers an impulse in a receptor, which travels along a sensory neuron to the central nervous system (CNS). The CNS coordinates a response and sends impulses along a motor neuron to an effector (muscle or gland). A reflex arc is a rapid, involuntary pathway that bypasses the brain, e.g. touching a hot object.
神经系统实现快速通讯。刺激在感受器引发神经冲动，沿感觉神经元传导至中枢神经系统（CNS）。中枢神经系统协调反应，将冲动沿运动神经元送至效应器（肌肉或腺体）。反射弧是一条快速的、不经大脑的不随意通路，例如碰到热物体。
The eye is an example of a sensory organ. Light enters through the cornea and pupil, is focused by the lens onto the retina, where rod and cone cells detect light and colour. The iris controls the amount of light entering by adjusting pupil size. Accommodation changes the lens shape to focus near and distant objects.
眼睛是感觉器官的一个例子。光线通过角膜和瞳孔进入，由晶状体聚焦到视网膜上，视杆细胞和视锥细胞检测光和颜色。虹膜通过调节瞳孔大小来控制进光量。眼的调节通过改变晶状体形状以聚焦近处和远处物体。
11. Reproduction | 生殖
Asexual reproduction produces genetically identical offspring from a single parent (mitosis). Examples include binary fission in bacteria, budding in yeast, and runners in plants. Sexual reproduction involves fusion of male and female gametes (sperm and egg) to form a zygote, giving genetic variation. Gametes are haploid (n) produced by meiosis.
无性生殖通过一个亲本产生遗传上相同的后代（有丝分裂）。例子包括细菌的二分裂、酵母的出芽生殖和植物的匍匐茎。有性生殖涉及雄性配子和雌性配子（精子和卵子）融合形成受精卵，产生遗传变异。配子是经减数分裂产生的单倍体（n）。
In humans, fertilisation occurs in the oviduct. The fertilised egg implants in the uterus wall and develops into an embryo. The placenta allows exchange of nutrients, gases and wastes between mother and foetus without mixing blood. The menstrual cycle is controlled by hormones including oestrogen and progesterone.
在人类中，受精发生在输卵管内。受精卵植入子宫壁并发育为胚胎。胎盘允许母亲和胎儿之间的营养物质、气体和废物交换，但血液不混合。月经周期由包括雌激素和孕酮在内的激素调控。
12. Inheritance | 遗传
Genes are sections of DNA that code for proteins. Alleles are different forms of a gene. Dominant alleles mask recessive ones. The genotype is the genetic constitution, while the phenotype is the observable characteristic. Monohybrid crosses show the inheritance of one trait, using Punnett squares to predict ratios (e.g. 3:1 in the F₂ generation for a dominant-recessive cross between heterozygotes).
基因是编码蛋白质的 DNA 片段。等位基因是同一基因的不同形式。显性等位基因掩盖隐性等位基因。基因型是遗传组成，而表现型是可观察的特征。单基因杂交显示一个性状的遗传，使用庞纳特方格预测比例（例如杂合子间显隐性杂交的 F₂ 代比例为 3:1）。
Sex-linked traits are carried on the X chromosome, e.g. colour blindness. Females have two X chromosomes (XX), males have XY. A male inherits an X-linked condition from his mother if she is a carrier. Codominance is when both alleles are expressed equally, as in AB blood type.
伴性性状位于 X 染色体上，如色盲。女性有两条 X 染色体（XX），男性有 XY。如果母亲是携带者，男性可从她那里遗传 X 连锁疾病。共显性指的是两个等位基因均等表达，如 AB 血型。
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