📚 GCSE Biology: End-of-Term Revision Guide | GCSE 生物：期末复习提纲
This comprehensive revision guide summarises the key topics covered in GCSE Biology, helping you consolidate your knowledge and identify areas for further study. Whether you are preparing for end-of-term exams or building a solid foundation, use this outline to check your understanding of essential concepts, from cell structure to ecology.
这份详尽的复习提纲汇总了 GCSE 生物学的核心主题，帮助你巩固知识并发现需要加强的部分。无论你是在准备期末考试还是夯实基础，都可以借助这份提纲检验自己对细胞结构到生态学等重要概念的理解。
The guide follows the logical order of most GCSE specifications: cells, enzymes and transport, cell division, photosynthesis and respiration, biological molecules, digestion, transport systems, health and immunity, nervous and hormonal control, genetics, evolution and ecology. Each section ends with the exam skills you are most likely to be tested on, so you can revise actively rather than simply rereading notes.
本提纲按照多数 GCSE 考纲的逻辑顺序编排：细胞、酶与运输、细胞分裂、光合作用与呼吸作用、生物分子、消化、运输系统、健康与免疫、神经与激素调节、遗传、进化与生态学。每一节都点出最可能考查的考试技能，帮助你主动复习，而不是被动重读笔记。
1. Cell Biology and Microscopy | 细胞生物学与显微镜
All organisms are composed of cells, the fundamental units of life. Cells can be prokaryotic (e.g., bacteria) lacking a true nucleus, or eukaryotic (e.g., plants, animals, fungi) possessing a membrane-bound nucleus that encloses genetic material. Prokaryotic cells are much smaller, usually 0.2-2 μm across, and carry a single circular loop of DNA plus small rings called plasmids.
所有生物都由细胞组成，细胞是生命的基本单位。细胞可分为原核细胞（如细菌），没有真正的细胞核；或真核细胞（如植物、动物、真菌），具有由膜包裹的细胞核，内含遗传物质。原核细胞小得多，通常直径 0.2-2 μm，只含一条环状 DNA 以及被称为质粒的小环状 DNA。
Animal and plant cells share common organelles: a nucleus that controls activities, mitochondria where aerobic respiration occurs, ribosomes for protein synthesis, and cytoplasm as the site of chemical reactions. Plant cells additionally have a rigid cellulose cell wall, a large permanent vacuole, and chloroplasts containing chlorophyll for photosynthesis.
动物细胞和植物细胞有一些共同的细胞器：控制活动的细胞核、进行有氧呼吸的线粒体、合成蛋白质的核糖体，以及化学反应发生的细胞质。植物细胞另外还有坚硬的纤维素细胞壁、一个大液泡和含叶绿素进行光合作用的叶绿体。
| Feature | Plant Cell | Animal Cell |
|---|---|---|
| Nucleus | Yes | Yes |
| Mitochondria | Yes | Yes |
| Cell wall (cellulose) | Yes | No |
| Chloroplasts | Yes (green parts) | No |
| Large permanent vacuole | Yes | No |
solution but kill the specimen. When calculating magnification, convert all lengths to the same unit first: 1 mm = 1000 μm and 1 μm = 1000 nm.
光学显微镜最多放大约 ×1500，分辨率约为 200 nm；电子显微镜放大倍数与分辨率都高得多，但会杀死样本。计算放大倍数时，必须先把所有长度换算成同一单位：1 mm = 1000 μm，1 μm = 1000 nm。
Magnification = Image size ÷ Actual size
2. Enzymes and Transport Across Membranes | 酶与跨膜运输
Enzymes are biological catalysts made of protein. They speed up reactions by lowering the activation energy needed, and they are specific because the substrate must fit the active site, the so-called lock and key model. The enzyme is not used up and can be reused many times.
酶是由蛋白质构成的生物催化剂。它们通过降低反应所需的活化能来加快反应速率，并具有专一性，因为底物必须与活性位点形状匹配，这就是通常所说的锁钥模型。酶本身不被消耗，可以反复使用。
Temperature and pH affect enzyme activity. Each enzyme has an optimum; human enzymes usually work best near 37 °C and pH 7, while stomach protease works best around pH 2. Beyond the optimum, bonds break, the active site changes shape and the enzyme becomes denatured, so activity falls sharply and never recovers.
温度和 pH 会影响酶的活性。每种酶都有最适条件；人体酶通常在 37 °C、pH 7 附近活性最高，而胃蛋白酶在 pH 2 左右活性最高。超过最适条件后，化学键断裂，活性位点形状改变，酶发生变性，活性急剧下降且不可恢复。
Substances cross membranes by diffusion, osmosis or active transport. Diffusion is the net movement of particles from high to low concentration, driven by the concentration gradient and affected by temperature, surface area and diffusion distance. Osmosis is the diffusion of water through a partially permeable membrane from a dilute solution to a concentrated one.
物质通过扩散、渗透或主动运输穿过细胞膜。扩散是粒子从高浓度向低浓度的净移动，由浓度梯度驱动，并受温度、表面积和扩散距离影响。渗透是水分子通过部分透性膜，从稀溶液向浓溶液方向的扩散。
Active transport moves substances against the concentration gradient and therefore requires energy from respiration plus carrier proteins in the membrane. Root hair cells use it to absorb mineral ions, and the small intestine uses it to absorb glucose when gut concentration is lower than blood concentration.
主动运输逆浓度梯度运输物质，因此需要呼吸作用提供的能量以及膜上的载体蛋白。根毛细胞用它吸收矿质离子；当肠内葡萄糖浓度低于血液浓度时，小肠也用它吸收葡萄糖。
Rate of reaction = 1 ÷ Time taken
3. Cell Division, Stem Cells and Chromosomes | 细胞分裂、干细胞与染色体
Body cells divide by mitosis to produce two genetically identical diploid daughter cells, each with the same chromosome number as the parent. In humans this is 46 chromosomes, or 23 pairs. Before division, the DNA is replicated in interphase so that each chromosome consists of two identical chromatids.
体细胞通过有丝分裂产生两个遗传上完全相同的二倍体子细胞，染色体数目与母细胞一致。人类的染色体数为 46 条，即 23 对。分裂前，DNA 在间期完成复制，因此每条染色体由两条完全相同的染色单体组成。
Mitosis is needed for growth, repair of damaged tissue and asexual reproduction. Bacteria divide by a simpler process called binary fission, which can occur every 20 minutes in ideal conditions and explains how infections spread rapidly inside the body.
有丝分裂用于生长、受损组织修复和无性繁殖。细菌则通过更简单的二分裂繁殖，在理想条件下每 20 分钟就能分裂一次，这也解释了感染为何在体内迅速扩散。
Stem cells are unspecialised cells that can divide and differentiate into specialised cells such as nerve, muscle or red blood cells. Embryonic stem cells can become almost any cell type, adult stem cells are more limited, and plant meristems at shoot and root tips provide a lifelong supply of new cells.
干细胞是未分化的细胞，能够分裂并分化成神经细胞、肌肉细胞或红细胞等特化细胞。胚胎干细胞几乎能变成任何细胞类型，成体干细胞的分化能力较有限，而植物茎尖和根尖的分生组织则能终生提供新细胞。
Possible medical uses include replacing damaged tissue in diabetes, Parkinson disease and spinal injury, but ethical issues arise from using embryos. Cancer is the result of uncontrolled mitosis caused by mutations in genes controlling the cell cycle, and tumours form when these cells keep dividing.
干细胞的医学用途包括替换糖尿病、帕金森病和脊髓损伤中受损的组织，但使用胚胎会引发伦理争议。癌症则是控制细胞周期的基因发生突变、有丝分裂失控的结果，这些细胞不断分裂便会形成肿瘤。
4. Photosynthesis and Respiration | 光合作用与呼吸作用
Photosynthesis is an endothermic reaction in which green plants, algae and some bacteria convert light energy into chemical energy stored in glucose. It occurs mainly in the palisade cells of leaves, which contain many chloroplasts and are packed near the upper surface.
光合作用是吸能反应，绿色植物、藻类和部分细菌把光能转化为储存在葡萄糖中的化学能。它主要发生在叶片的栅栏组织中，这些细胞含大量叶绿体并靠近叶片上表面紧密排列。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
The rate of photosynthesis is limited by light intensity, carbon dioxide concentration and temperature. Whichever factor is in shortest supply becomes the limiting factor, and increasing the others will not raise the rate until that factor is also increased. Temperature is limiting because the reactions are controlled by enzymes.
光合作用速率受光照强度、二氧化碳浓度和温度限制。供应最不足的那个因素即为限制因素，在它提高之前，增加其他因素都不会提升速率。温度之所以成为限制因素，是因为这些反应由酶控制。
Practical work often uses pondweed, counting oxygen bubbles released per minute at different distances from a lamp, or measuring the volume of gas collected. Greenhouses use this knowledge by adding carbon dioxide, artificial light and heaters to increase crop yield.
实验常用水绵或水草，通过改变与灯泡的距离，计数每分钟释放的氧气气泡，或测量收集到的气体体积。温室则应用这些原理，通过补充二氧化碳、人工光照和加温来提高作物产量。
Aerobic respiration releases much more energy and takes place mainly in the mitochondria.
有氧呼吸释放的能量多得多，主要在线粒体中进行。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
Anaerobic respiration happens without oxygen. In muscles, glucose is converted to lactic acid, which builds up and causes fatigue and cramp; the extra oxygen needed to break it down afterwards is called the oxygen debt. In yeast and plant cells, glucose is converted to ethanol and carbon dioxide, a process used in bread making and brewing.
无氧呼吸在无氧条件下发生。在肌肉中，葡萄糖转化为乳酸，乳酸积累会引起疲劳和抽筋；事后分解乳酸所需的额外氧气称为氧债。在酵母和植物细胞中，葡萄糖转化为乙醇和二氧化碳，这一过程被用于制作面包和酿酒。
5. Biological Molecules and Food Tests | 生物分子与食物检测
Living organisms are built from four main groups of biological molecules: carbohydrates, proteins, lipids and nucleic acids. Carbohydrates such as starch and glycogen are made of simple sugars and act as energy stores; proteins are polymers of amino acids used for growth and repair; lipids store energy and form cell membranes.
生物体主要由四大类生物分子构成：碳水化合物、蛋白质、脂质和核酸。淀粉、糖原等碳水化合物由单糖组成，充当能量储存物质；蛋白质是氨基酸的聚合物，用于生长与修复；脂质既能储存能量，又是细胞膜的组成成分。
Food tests identify these molecules quickly. Starch turns iodine solution blue-black, reducing sugars turn Benedict solution from blue through green and yellow to brick red after heating in a water bath, protein turns Biuret reagent purple, and lipids form a white emulsion when shaken with ethanol and water.
食物检测可以快速鉴定这些分子。淀粉遇碘液变蓝黑色；还原糖在本尼迪特试剂中水浴加热后，由蓝色依次变为绿色、黄色直至砖红色沉淀；蛋白质使双缩脲试剂变紫；脂质与乙醇和水振荡后形成白色乳浊液。
| Test | Reagent | Positive Result |
|---|---|---|
| Starch | Iodine solution | Blue-black |
| Reducing sugar | Benedict solution | Brick red precipitate |
| Protein | Biuret reagent | Purple |
| Lipid | Ethanol + water | White emulsion |
Energy requirements vary with age, sex and activity level. A diet too high in energy leads to obesity, which raises the risk of type 2 diabetes and cardiovascular disease, while a diet too low in energy causes malnutrition. Body mass index and waist-to-hip ratio are simple measures used to assess body composition.
能量需求随年龄、性别和活动量而变化。能量摄入过高会导致肥胖，进而增加 2 型糖尿病和心血管疾病的风险；摄入过低则造成营养不良。体质指数和腰臀比是评估身体成分的简单指标。
6. Digestion and the Digestive System | 消化与消化系统
Digestion converts large insoluble molecules into small soluble ones that can be absorbed into the blood. Mechanical digestion begins in the mouth, where teeth break food into smaller pieces to increase the surface area for enzymes, and the tongue forms a bolus for swallowing.
消化把大分子不溶性物质转化为可被吸收入血的小分子可溶性物质。机械性消化从口腔开始，牙齿把食物切碎以增大酶作用的表面积，舌头则把食物团成食团以便吞咽。
Three main groups of digestive enzymes work in the gut. Carbohydrase, including amylase from salivary glands and the pancreas, breaks starch into maltose and then glucose. Protease from the stomach, pancreas and small intestine breaks protein into amino acids. Lipase from the pancreas breaks lipids into fatty acids and glycerol.
肠道中有三类主要的消化酶。淀粉酶类（包括唾液腺和胰腺分泌的淀粉酶）把淀粉分解为麦芽糖，再分解为葡萄糖；胃、胰腺和小肠分泌的蛋白酶把蛋白质分解为氨基酸；胰腺分泌的脂肪酶把脂质分解为脂肪酸和甘油。
Bile is produced by the liver, stored in the gall bladder, and released into the small intestine. It is alkaline, so it neutralises hydrochloric acid from the stomach and provides the optimum pH for pancreatic enzymes. It also emulsifies lipids into tiny droplets, increasing surface area for lipase.
胆汁由肝脏产生、储存在胆囊中并释放到小肠。它是碱性的，可以中和胃酸，为胰酶提供最适 pH；同时把脂质乳化成小油滴，增大脂肪酶作用的表面积。
The small intestine is adapted for absorption with villi and microvilli that greatly increase surface area, a wall only one cell thick for a short diffusion path, and a dense network of capillaries that carries absorbed nutrients away and maintains a steep concentration gradient.
小肠通过绒毛和微绒毛极大增大吸收面积，肠壁仅一个细胞厚，扩散距离很短；此外还有密集的毛细血管网将吸收的营养物质运走，维持陡峭的浓度梯度。
7. Transport Systems: Blood, Heart and Plants | 运输系统：血液、心脏与植物
Blood is a tissue made of plasma, red blood cells, white blood cells and platelets. Red blood cells have no nucleus, are biconcave in shape and contain haemoglobin, which binds oxygen in the lungs and releases it in respiring tissues. White blood cells defend the body, while platelets help blood clot at wounds.
血液是一种由血浆、红细胞、白细胞和血小板组成的组织。红细胞没有细胞核，呈双凹圆盘状，内含血红蛋白，在肺部结合氧气并在呼吸旺盛的组织中释放。白细胞负责防御，血小板则帮助伤口凝血。
The heart has four chambers and a double circulatory system. Deoxygenated blood returns to the right atrium, passes to the right ventricle and is pumped to the lungs; oxygenated blood returns to the left atrium and is pumped by the thicker-walled left ventricle to the whole body. Valves prevent backflow.
心脏有四个腔室，人体具有双循环系统。缺氧血回到右心房，进入右心室后泵向肺；含氧血回到左心房，由壁更厚的左心室泵向全身。瓣膜防止血液倒流。
Coronary heart disease is caused by fatty deposits narrowing the coronary arteries, reducing oxygen supply to heart muscle. Treatments include stents to hold arteries open, statins to lower cholesterol, and lifestyle changes such as stopping smoking and taking regular exercise. Faulty valves can be replaced, and an artificial pacemaker can correct irregular heart rhythm.
冠心病由脂肪沉积使冠状动脉变窄、心肌供氧减少所致。治疗手段包括用支架撑开血管、用他汀类药物降低胆固醇，以及戒烟和规律运动
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