📚 Year 11 CIE IGCSE Biology Core Concepts Review | Year 11 CIE 生物：核心知识点梳理
This article provides a structured review of the core topics in the CIE IGCSE Biology syllabus for Year 11 students. Each section covers essential concepts, key processes and common examination points, presented in a bilingual format to support both English-medium and Chinese-speaking learners. Mastering these fundamentals will build a solid foundation for success in the IGCSE Biology exam.
本文为 Year 11 学生系统梳理 CIE IGCSE 生物课程的核心知识点。每一部分涵盖重要概念、关键过程及常见考点，并以双语形式呈现，便于英文授课及中文背景的学习者掌握。扎实理解这些基础内容将为 IGCSE 生物考试的成功奠定牢固根基。
1. Cell Structure and Organisation | 细胞结构与组织
All living organisms are made of cells, which are the basic structural and functional units of life. Cells can be prokaryotic (e.g., bacteria) or eukaryotic (plants, animals, fungi). Key organelles include the nucleus, which contains genetic material; mitochondria, the sites of aerobic respiration; ribosomes for protein synthesis; and the cell membrane, which controls the entry and exit of substances. Plant cells also have a rigid cell wall, chloroplasts for photosynthesis and a large permanent vacuole supporting turgor.
所有生物均由细胞构成，细胞是生命的基本结构和功能单位。细胞分为原核细胞（如细菌）和真核细胞（植物、动物、真菌）。重要细胞器包括：含有遗传物质的细胞核；有氧呼吸的场所线粒体；合成蛋白质的核糖体；以及控制物质进出的细胞膜。植物细胞还具有坚硬的细胞壁、进行光合作用的叶绿体和支持膨压的大液泡。
In multicellular organisms, cells become specialised to carry out specific functions. Examples include red blood cells, which have a biconcave shape and no nucleus to maximise haemoglobin and oxygen transport; root hair cells, which have a long extension to absorb water and minerals; and ciliated epithelial cells that move mucus in the trachea. Cells are organised into tissues, organs and organ systems such as the digestive system.
在多细胞生物中，细胞发生特化以执行特定功能。例如，红细胞呈双凹圆盘状且无细胞核，以容纳最大量的血红蛋白运输氧气；根毛细胞具有长突起以吸收水分和矿物质；纤毛上皮细胞在气管中摆动以移动黏液。细胞进而构成组织、器官和器官系统，如消化系统。
image size ÷ actual size. When using a light microscope, specimens are often stained with iodine or methylene blue to make structures visible. Remember to convert all measurements to the same unit before calculating.
放大倍数计算是核心的实验技能。放大倍数 = 图像大小 ÷ 实际大小。使用光学显微镜时，常用碘液或亚甲蓝对标本染色，以便观察结构。计算前务必将所有单位统一。
2. Movement in and out of Cells | 物质进出细胞
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 a passive process that does not require energy. Factors affecting the rate of diffusion include temperature, concentration gradient and surface area. Examples in living organisms are the movement of oxygen into cells and carbon dioxide out of leaves through stomata.
扩散是粒子从高浓度区域向低浓度区域的净移动，沿着浓度梯度进行。这是一个被动过程，不需要能量。影响扩散速率的因素包括温度、浓度梯度和表面积。生物体内的例子有氧气进入细胞以及二氧化碳通过气孔从叶片排出。
Osmosis is the movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane. In plant cells, when placed in a dilute solution, water enters by osmosis, causing the cell to become turgid. In a concentrated solution, water leaves, and the cell becomes plasmolysed. Animal cells lack a cell wall and may burst or shrink in extreme solutions.
渗透作用是水分子通过半透膜从较高水势区域向较低水势区域的移动。在植物细胞中，置于稀溶液时，水因渗透进入，细胞变得硬挺；在浓溶液中，水流失，细胞发生质壁分离。动物细胞没有细胞壁，在极端溶液中可能胀破或皱缩。
Active transport is the movement of particles against a concentration gradient, from a lower to a higher concentration, using energy from ATP. Carrier proteins in the cell membrane are required. An example is the absorption of mineral ions by root hair cells from the soil, where ion concentrations are lower than inside the cell.
主动运输是粒子逆浓度梯度从低浓度向高浓度的移动，需要消耗来自 ATP 的能量，并依赖细胞膜上的载体蛋白。例子有根毛细胞从土壤中吸收矿质离子，尽管土壤中的离子浓度低于胞内。
3. Biological Molecules and Enzymes | 生物分子与酶
Carbohydrates, proteins and lipids are the main biological molecules. Starch and glycogen are storage polysaccharides; glucose is a simple sugar used in respiration. Proteins are made of amino acids and have many functions, including enzymes. Lipids (fats and oils) are composed of fatty acids and glycerol and are important energy stores and insulation.
碳水化合物、蛋白质和脂质是主要的生物分子。淀粉和糖原是储存多糖；葡萄糖是用于呼吸作用的一种单糖。蛋白质由氨基酸构成，具有多种功能，包括作为酶。脂质（脂肪和油）由脂肪酸和甘油组成，是重要的能量储存物质和绝缘体。
Food tests are standard practicals. Iodine solution turns blue-black in the presence of starch. Benedict's solution gives a brick-red precipitate when heated with reducing sugars. Biuret reagent turns purple if protein is present. The emulsion test for lipids involves mixing with ethanol and pouring into water; a cloudy white emulsion indicates lipid.
食物检测是标准实验。碘液遇淀粉变蓝黑色。本尼迪克特溶液与还原糖共热产生砖红色沉淀。双缩脲试剂遇蛋白质呈紫色。脂质的乳浊液测试：将样品与乙醇混合后倒入水中，若出现白色乳浊液则含脂质。
Enzymes are biological catalysts that speed up reactions by lowering activation energy. They are proteins with an active site complementary to the substrate. The 'lock and key' model describes this specificity. Enzyme activity is affected by temperature and pH; each enzyme has an optimum. High temperatures or extreme pH cause denaturation, where the active site changes shape irreversibly.
酶是生物催化剂，通过降低活化能来加速反应。酶是蛋白质，其活性位点与底物互补，“锁钥模型”描述了这种特异性。酶活性受温度和 pH 影响，每种酶都有最适条件。高温或极端 pH 导致变性，活性位点永久改变形状而失活。
4. Plant Nutrition and Photosynthesis | 植物营养与光合作用
Photosynthesis is the process by which plants manufacture carbohydrates using light energy. The balanced equation is:
光合作用是植物利用光能制造碳水化合物的过程。平衡方程式如下：
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Chlorophyll inside chloroplasts absorbs light energy, which is used to split water (photolysis) and produce oxygen as a by-product. The glucose formed can be converted into starch for storage, cellulose for cell walls, or used in respiration.
叶绿体中的叶绿素吸收光能，用于光解水并产生氧气作为副产物。生成的葡萄糖可转化为淀粉储存、构成细胞壁的纤维素，或用于呼吸作用。
Limiting factors for photosynthesis are light intensity, carbon dioxide concentration and temperature. A factor becomes limiting when its supply restricts the rate. In experiments using aquatic plants, the rate of bubble production can indicate photosynthetic rate. A destarched leaf can be tested for starch after exposure to light; any blue-black colour with iodine confirms starch production.
光合作用的限制因素有光照强度、二氧化碳浓度和温度。当某一因素供应不足时，就会成为限制因子，减慢光合速率。利用水生植物的实验中，气泡释放速率可指示光合速率。对饥饿处理的叶片照光后再用碘液测试淀粉，若出现蓝黑色则证明产生了淀粉。
5. Human Nutrition and Digestion | 人类营养与消化
A balanced diet includes carbohydrates, proteins, lipids, vitamins, minerals, fibre and water. Deficiencies cause disorders such as scurvy (vitamin C deficiency) and anaemia (iron deficiency). Mechanical digestion breaks food into smaller pieces; chemical digestion uses enzymes to break large insoluble molecules into small soluble ones for absorption.
均衡饮食包含碳水化合物、蛋白质、脂质、维生素、矿物质、膳食纤维和水。缺乏会引起疾病，如坏血病（维生素 C 缺乏）和贫血（缺铁）。物理性消化将食物磨碎；化学性消化利用酶将大分子不溶性物质分解为可吸收的小分子。
The key digestive enzymes and their actions are summarised below:
关键消化酶及其作用总结如下：
| Enzyme | Site of action | Substrate | Product |
|---|---|---|---|
| Amylase | Mouth, small intestine | Starch | Maltose |
| Protease | Stomach, pancreas, small intestine | Protein | Amino acids |
| Lipase | Pancreas, small intestine | Fats (lipids) | Fatty acids and glycerol |
Bile, produced by the liver and stored in the gall bladder, is not an enzyme but emulsifies fats, increasing the surface area for lipase action. The small intestine is lined with villi which have a large surface area, thin walls and a good blood supply to absorb digested food efficiently.
由肝脏产生并储存在胆囊的胆汁虽然不是酶，但能乳化脂肪，增大脂肪酶作用的表面积。小肠内壁布满绒毛，具有较大的表面积、薄壁和丰富的血液供应，可高效吸收消化产物。
6. Respiration and Gas Exchange | 呼吸与气体交换
Respiration is the release of energy from food and occurs in every living cell. Aerobic respiration uses oxygen and produces carbon dioxide, water and a large amount of energy:
呼吸是细胞从食物中释放能量的过程，发生于所有活细胞。有氧呼吸利用氧气，产生二氧化碳、水和大量能量：
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
Anaerobic respiration occurs without oxygen. In yeast, it produces ethanol and carbon dioxide (fermentation); in human muscles during vigorous exercise, it produces lactic acid, which causes fatigue and oxygen debt. Anaerobic respiration releases much less energy than aerobic.
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）；在人体肌肉剧烈运动时产生乳酸，引起疲劳和氧债。无氧呼吸释放的能量远少于有氧呼吸。
The human gas exchange system includes the trachea, bronchi, bronchioles and alveoli. Alveoli are the sites of gas exchange; they have moist thin walls, are surrounded by capillaries and provide a large surface area. Inspired air contains more oxygen and less carbon dioxide than expired air. Tar in cigarette smoke paralyses cilia, and carbon monoxide reduces the oxygen-carrying capacity of red blood cells.
人体气体交换系统包括气管、支气管、细支气管和肺泡。肺泡是气体交换的部位，具有湿润、薄壁、包围着毛细血管的特点，并提供了巨大的表面积。吸入气比呼出气含更多的氧气和更少的二氧化碳。香烟烟雾中的焦油会使纤毛麻痹，一氧化碳会降低红细胞携氧能力。
7. Transport in Plants and Animals | 动植物运输
In plants, xylem vessels transport water and dissolved minerals from roots to leaves. Xylem cells are dead, hollow and strengthened by lignin. Transpiration pull, caused by evaporation of water from stomata, draws water up the plant. Factors affecting transpiration rate include light intensity, temperature, humidity and wind speed. Phloem transports sucrose and amino acids (translocation) in both directions.
在植物中，木质部导管将水和溶解的矿质从根部运输到叶片。木质部细胞是死细胞，中空并由木质素加固。由气孔水分蒸发引起的蒸腾拉力将水向上拉。影响蒸腾速率的因素有光照强度、温度、湿度和风速。韧皮部则双向运输蔗糖和氨基酸（转运）。
Mammals have a double circulatory system: the right side of the heart pumps deoxygenated blood to the lungs (pulmonary circulation), while the left side pumps oxygenated blood to the body (systemic circulation). The heart has four chambers: two atria and two ventricles. The left ventricle has a thicker muscular wall because it must pump blood around the whole body. The pacemaker (sinoatrial node) controls heart rate.
哺乳动物具有双循环系统：右心将缺氧血泵至肺部（肺循环），左心将富氧血泵至全身（体循环）。心脏有四个腔：两个心房和两个心室。左心室肌肉壁更厚，因为它需要将血液泵送至全身。起搏点（窦房结）控制心率。
Arteries carry blood away from the heart under high pressure and have thick elastic walls. Veins return blood to the heart at lower pressure and contain valves to prevent backflow. Capillaries are one-cell thick tubes where exchange of materials occurs. Blood consists of plasma, red blood cells, white blood cells and platelets.
动脉将血液在高压下运离心脏，管壁厚而有弹性。静脉在低压下将血液送回心脏，含有瓣膜以防止回流。毛细血管是单层细胞厚度的管道，是物质交换的场所。血液由血浆、红细胞、白细胞和血小板组成。
8. Homeostasis and Excretion | 稳态与排泄
Homeostasis is the maintenance of a constant internal environment. Excretion is the removal of toxic waste products of metabolism, primarily urea, carbon dioxide and excess salts. The kidneys filter blood to form urine. Each kidney contains millions of nephrons; ultrafiltration occurs in the glomerulus, and selective reabsorption of glucose, some ions and water happens in the tubule.
稳态是指维持恒定的内环境。排泄是移除代谢产生的有毒废物，主要是尿素、二氧化碳和多余的盐。肾通过过滤血液形成尿液。每个肾含有数百万个肾单位；超滤作用发生在肾小球，而葡萄糖、部分离子和水在肾小管中被选择性地重吸收。
The skin also helps maintain homeostasis by regulating body temperature. In hot conditions, sweat glands secrete sweat (cooling by
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