AS CAIE Biology: Full Syllabus Breakdown | AS CAIE 生物：课程大纲全面解析

📚 AS CAIE Biology: Full Syllabus Breakdown | AS CAIE 生物：课程大纲全面解析

The Cambridge International AS Level Biology syllabus (9700) provides a rigorous foundation in biological principles, from the chemistry of life to whole-organism physiology. Designed to be taught over one academic year, it equips students with both theoretical knowledge and practical skills assessed through a combination of multiple-choice, structured, and practical examination papers. This article presents a detailed chapter-by-chapter breakdown of every topic you need to master, along with an overview of the assessment structure and essential study tips.

剑桥国际 AS 生物教学大纲（9700）为生物学原理打下了扎实的基础，内容涵盖从生命化学到整体生理学的各个方面。课程设计为一年制，通过选择题、结构化问答题和实验考试的综合评估，既考核理论知识也锻炼实践技能。本文将对每个必考章节进行详尽解析，同时简述评估框架并提供核心备考建议，帮助你全面掌握 AS 生物的脉络。

1. Overview of the AS Biology Syllabus | AS 生物课程大纲概览

The CAIE AS Biology qualification consists of three examination papers. Paper 1 is a 40-mark multiple-choice test lasting 1 hour 15 minutes, assessing breadth of knowledge across all 11 chapters. Paper 2 contains structured questions worth 60 marks (1 hour 15 minutes) and focuses on deeper understanding and application. Paper 3 is the practical paper (40 marks, 2 hours), evaluating experimental skills, data handling, and evaluation. The syllabus content is organised into 11 sections, and a percentage weight is not officially specified, but all topics are examinable. The table below summarises the key themes.

CAIE AS 生物学资质评估包含三场考试。试卷一为 40 道选择题，时长 1 小时 15 分钟，考察全部 11 个章节的知识广度。试卷二为结构化问答题，满分 60 分（1 小时 15 分钟），侧重深度理解和应用。试卷三是实验卷（40 分，2 小时），评估实验操作、数据处理和评价能力。考纲内容分 11 个主题，官方未明确权重，但所有主题均会考察。下表概括了各章核心主题。

Chapter	Core Theme	章节	核心主题
1	Cell Structure	1	细胞结构
2	Biological Molecules	2	生物分子
3	Enzymes	3	酶
4	Cell Membranes and Transport	4	细胞膜与物质运输
5	The Mitotic Cell Cycle	5	有丝分裂细胞周期
6	Nucleic Acids and Protein Synthesis	6	核酸与蛋白质合成
7	Transport in Plants	7	植物运输
8	Transport in Mammals	8	哺乳动物运输
9	Gas Exchange and Smoking	9	气体交换与吸烟
10	Infectious Disease	10	传染病
11	Immunity	11	免疫

2. Cell Structure | 细胞结构

In AS Biology, understanding cell ultrastructure is fundamental. You must be able to interpret electron micrographs and recognise key organelles in both animal and plant cells. The nucleus, mitochondria, rough and smooth endoplasmic reticulum, Golgi apparatus, ribosomes, lysosomes, centrioles, chloroplasts, cell wall, and vacuole all have distinct functions that link to the way cells specialise.

在 AS 生物学中，理解细胞超微结构是基础。你必须能够解读电子显微照片，识别动植物细胞中的关键细胞器。细胞核、线粒体、粗面和滑面内质网、高尔基体、核糖体、溶酶体、中心粒、叶绿体、细胞壁和液泡各自具有独特的功能，这些功能与细胞的特化方式紧密相关。

Prokaryotic cells, such as bacteria, lack a true nucleus and membrane-bound organelles. Instead they have a circular DNA molecule, 70S ribosomes, a cell wall containing peptidoglycan, and sometimes a capsule, plasmids, and flagella. Viruses are acellular, consisting only of genetic material surrounded by a protein coat, and require a host cell to replicate.

原核细胞（如细菌）没有真正的细胞核和膜包被的细胞器。它们含有环状 DNA、70S 核糖体、含肽聚糖的细胞壁，有时还具有荚膜、质粒和鞭毛。病毒是非细胞结构，仅由遗传物质和蛋白质外壳组成，必须依赖宿主细胞才能复制。

The relationship between structure and function is tested heavily. For example, the inner membrane of mitochondria is folded into cristae to increase surface area for ATP production, while the extensive rough ER provides a large surface for protein synthesis and transport.

结构与功能的关系是高频考点。例如，线粒体内膜向内折叠形成嵴，增大了 ATP 产生的表面积；而广阔的粗面内质网则为蛋白质合成和运输提供了巨大的工作面积。

3. Biological Molecules | 生物分子

The chemistry of life revolves around carbohydrates, lipids, proteins, and water. Carbohydrates include monosaccharides (such as glucose, formula C₆H₁₂O₆), disaccharides (e.g. sucrose, maltose) formed by condensation reactions, and polysaccharides like starch, glycogen, and cellulose. You need to relate the structure of these polysaccharides to their roles—starch as a compact energy store, cellulose providing tensile strength in plant cell walls through hydrogen-bonded microfibrils.

生命化学围绕碳水化合物、脂质、蛋白质和水展开。碳水化合物包括单糖（如葡萄糖，分子式 C₆H₁₂O₆）、通过缩合反应形成的二糖（如蔗糖、麦芽糖），以及淀粉、糖原和纤维素等多糖。你需要将多糖的结构与其角色联系起来——淀粉是紧凑的能量储存形式，纤维素通过氢键连接的微纤维为植物细胞壁提供抗拉强度。

Lipids, especially triglycerides, are esters of glycerol and three fatty acids. Their hydrophobic nature makes them ideal for long-term energy storage, insulation, and forming the core of cell membranes. Phospholipids are structurally similar but have a phosphate-containing head that is hydrophilic, enabling the formation of the bilayer.

脂质，特别是甘油三酯，是甘油与三个脂肪酸形成的酯。其疏水性使其成为长期储能、保温和构成细胞膜核心的理想分子。磷脂结构类似，但含有一个亲水的磷酸头部，从而能形成双分子层。

Proteins are polymers of amino acids linked by peptide bonds. Their primary structure is the sequence of amino acids; secondary structures include alpha-helices and beta-pleated sheets held by hydrogen bonds; tertiary structure involves further folding due to interactions between R groups; and quaternary structure applies to proteins with multiple subunits. The syllabus also requires biochemical tests: Benedict’s test for reducing sugars, iodine for starch, biuret for proteins, and the emulsion test for lipids.

蛋白质是氨基酸通过肽键连接而成的聚合物。一级结构是氨基酸序列；二级结构包括由氢键维持的 α-螺旋和 β-折叠；三级结构因 R 基团间相互作用而进一步折叠；四级结构适用于具有多个亚基的蛋白质。大纲还要求掌握生化测试：本尼迪克特试验测还原糖，碘液测淀粉，双缩脲测蛋白质，以及乳浊试验测脂质。

4. Enzymes | 酶

Enzymes are globular proteins acting as biological catalysts that lower activation energy without being consumed. Their specificity arises from the complementary shape of the active site to the substrate, explained by the lock-and-key model and, more accurately, the induced-fit model where the active site undergoes a conformational change upon substrate binding.

酶是球状蛋白质，作为生物催化剂能降低活化能而自身不被消耗。其专一性源于活性位点与底物形状的互补性，可以用“锁钥模型”解释，更准确的“诱导契合模型”则认为底物结合会导致活性位点构象发生变化。

You must explain the effects of temperature, pH, enzyme concentration, and substrate concentration on the rate of enzyme-catalysed reactions. At low temperatures, molecules have little kinetic energy, so collisions are infrequent. As temperature rises, the rate increases until the enzyme denatures and the active site loses its specific shape. Extreme pH can also disrupt ionic and hydrogen bonds, causing denaturation. The concept of Vmax and the Michaelis-Menten constant (Km) is introduced at AS, but detailed calculations are not required; instead, the focus is on interpreting graphs and understanding saturation kinetics.

你需要解释温度、pH、酶浓度和底物浓度对酶促反应速率的影响。低温下分子动能低，碰撞频率小；温度升高，速率增加，直至酶变性、活性位点失去特定形状。极端 pH 也会破坏离子键和氢键导致变性。AS 阶段引入 Vmax 和米氏常数 (Km) 的概念，但无需详细计算；重点在于解读曲线图和理解饱和动力学。

Competitive inhibitors bind to the active site, competing with the substrate, and their effect can be overcome by increasing substrate concentration. Non-competitive inhibitors bind to an allosteric site, altering the enzyme’s shape so that the active site is no longer functional; increasing substrate concentration does not reverse this. Immobilised enzymes and their industrial uses, such as in biosensors or lactose-free milk production, are also part of the syllabus.

竞争性抑制剂与活性位点结合，与底物竞争，可通过增加底物浓度克服其影响。非竞争性抑制剂与别构位点结合，改变酶的形状，使活性位点失效；增加底物浓度无法逆转。固定化酶及其在工业中的应用，如生物传感器或无乳糖牛奶生产，也是大纲内容。

E + S ⇌ ES → E + P

5. Cell Membranes and Transport | 细胞膜与物质运输

The fluid mosaic model describes the cell membrane as a phospholipid bilayer with embedded proteins, cholesterol, glycolipids, and glycoproteins. Phospholipids move laterally, giving the membrane fluidity, while cholesterol regulates fluidity and stability. Transport proteins function as channel or carrier proteins for facilitated diffusion and active transport.

流动镶嵌模型将细胞膜描述为磷脂双分子层，其中嵌有蛋白质、胆固醇、糖脂和糖蛋白。磷脂可横向移动，赋予膜流动性，胆固醇则调节流动性和稳定性。转运蛋白充当通道蛋白或载体蛋白，参与协助扩散和主动运输。

You must distinguish between simple diffusion, facilitated diffusion, osmosis, and active transport. Diffusion is the net movement of particles down a concentration gradient; facilitated diffusion uses protein channels or carriers but still moves substances down their gradient. Osmosis is the net movement of water from a region of higher water potential to a region of lower water potential through a partially permeable membrane. Active transport requires energy in the form of ATP to move substances against a concentration gradient via carrier proteins, such as the sodium-potassium pump.

你必须区分简单扩散、协助扩散、渗透和主动运输。扩散是粒子沿浓度梯度的净移动；协助扩散利用蛋白质通道或载体，但仍沿浓度梯度进行。渗透是水通过部分通透膜从高水势区域向低水势区域的净移动。主动运输需要 ATP 形式的能量，通过载体蛋白逆浓度梯度运输物质，例如钠-钾泵。

Bulk transport via endocytosis and exocytosis allows large particles or macromolecules to cross the membrane. Endocytosis involves the engulfing of material by the membrane to form a vesicle; exocytosis fuses vesicles with the membrane to secrete contents. The practical investigation of osmosis using potato strips or beetroot is common in Paper 3.

通过内吞和外排进行的批量运输，使大颗粒或大分子能穿过膜。内吞是膜包裹物质形成囊泡；外排则是囊泡与膜融合分泌内容物。用土豆条或甜菜根研究渗透作用的实验常见于试卷三。

6. The Mitotic Cell Cycle | 有丝分裂细胞周期

The cell cycle consists of interphase (G1, S, G2) and the mitotic phase. During interphase, the cell grows, replicates its DNA during S phase, and synthesises proteins necessary for division. Mitosis itself is divided into prophase, metaphase, anaphase, and telophase, followed by cytokinesis.

细胞周期包括间期（G1、S、G2）和有丝分裂期。间期细胞生长，在 S 期复制 DNA，并合成分裂所需的蛋白质。有丝分裂本身分为前期、中期、后期和末期，随后是胞质分裂。

You need to describe the behaviour of chromosomes in each stage. In prophase, chromosomes condense and become visible as two sister chromatids joined at the centromere; the nuclear envelope breaks down. During metaphase, chromosomes align at the equator, attached to spindle fibres by their centromeres. Anaphase involves the separation of sister chromatids as spindle fibres shorten, pulling them to opposite poles. Telophase sees the formation of new nuclear envelopes around each set of chromosomes, which decondense. Mitosis produces two genetically identical daughter cells, essential for growth, repair, and asexual reproduction.

你需要描述各阶段染色体的行为。前期，染色体凝集，可见两条姐妹染色单体由着丝粒相连；核膜解体。中期，染色体排列在赤道板上，由着丝粒与纺锤丝相连。后期，纺锤丝缩短，姐妹染色单体分离并被拉向两极。末期，每组染色体周围形成新的核膜，染色体解旋。有丝分裂产生两个遗传上完全相同的子细胞，对生长、修复和无性繁殖至关重要。

Uncontrolled cell division can lead to cancer. The role of oncogenes and tumour suppressor genes in regulating the cell cycle is introduced, along with the concept that mutations in these genes can disrupt normal control, causing tumours.

细胞分裂失控可导致癌症。大纲介绍了原癌基因和抑癌基因调控细胞周期的作用，以及这些基因突变可扰乱正常控制，导致肿瘤产生。

7. Nucleic Acids and Protein Synthesis | 核酸与蛋白质合成

DNA (deoxyribonucleic acid) is a double-stranded polynucleotide with a sugar-phosphate backbone and complementary base pairing: adenine with thymine, cytosine with guanine. RNA (ribonucleic acid) is usually single-stranded, contains ribose instead of deoxyribose, and has uracil in place of thymine. You should be able to describe the structure of a nucleotide—composed of a nitrogenous base, a pentose sugar, and a phosphate group.

DNA（脱氧核糖核酸）是双链多核苷酸，具有糖磷酸骨架和互补碱基配对：腺嘌呤与胸腺嘧啶配对，胞嘧啶与鸟嘌呤配对。RNA（核糖核酸）通常是单链，含核糖而非脱氧核糖，并且用尿嘧啶代替胸腺嘧啶。你应能描述核苷酸的结构——由含氮碱基、五碳糖和磷酸基团组成。

DNA replication is semi-conservative, meaning each new DNA molecule contains one original strand and one newly synthesised strand. The enzyme helicase unwinds the double helix and breaks hydrogen bonds; DNA polymerase assembles new complementary strands using free nucleotides, in the 5′ to 3′ direction. The Meselson-Stahl experiment provided evidence for semi-conservative replication.

DNA 复制是半保留的，即每条新 DNA 分子含有一条母链和一条新合成的链。解旋酶解开双螺旋并断裂氢键；DNA 聚合酶以游离核苷酸为原料，沿 5′ 到 3′ 方向合成新的互补链。梅塞尔森-斯塔尔实验为半保留复制提供了证据。

Protein synthesis involves transcription and translation. In transcription, a gene’s DNA sequence is copied into messenger RNA (mRNA) by RNA polymerase. The mRNA then moves to the cytoplasm, where ribosomes translate the sequence in sets of three bases (codons) into a polypeptide chain. Transfer RNA (tRNA) molecules bring specific amino acids, with anticodons pairing with mRNA codons. Mutations such as substitution, deletion, or insertion can alter the amino acid sequence and potentially the protein’s function. Sickle cell anaemia is a classic example of a single base substitution causing a change in haemoglobin.

蛋白质合成包括转录和翻译。转录时，RNA 聚合酶将基因的 DNA 序列拷贝为信使 RNA (mRNA)。mRNA 随后进入细胞质，在核糖体上以三联体碱基（密码子）形式翻译成多肽链。转运 RNA (tRNA) 携带特定氨基酸，其反密码子与 mRNA 密码子配对。替换、缺失或插入等突变可改变氨基酸序列并可能影响蛋白质功能。镰刀型细胞贫血是单碱基替换导致血红蛋白变化的经典例子。

DNA → mRNA → Protein

8. Transport in Plants | 植物运输

Plants have two major transport systems: the xylem, which transports water and dissolved minerals upwards from the roots, and the phloem, which transports sucrose and amino acids from sources to sinks (translocation). You need to relate the structure of xylem vessels—dead, hollow tubes with lignified walls—and phloem sieve tubes with companion cells to their functions.

植物有两大运输系统：木质部向上运输水和溶解的矿物质，韧皮部将蔗糖和氨基酸从源运输到库（转运）。你需要将木质部导管（死细胞、中空、壁木质化）和韧皮部筛管与伴胞的结构与其功能相联系。

Water movement through the plant follows the transpiration stream. Water evaporates from mesophyll cells into leaf air spaces and diffuses out through stomata; this creates a negative pressure potential that pulls water up the xylem. Cohesion between water molecules and adhesion to xylem walls (capillarity) help maintain the continuous column. Factors affecting transpiration rate include light intensity, temperature, humidity, and wind speed, and these can be investigated using a potometer.

水分在植物体内沿蒸腾流移动。水从叶肉细胞蒸发进入细胞间隙，经气孔扩散出去；这产生负压势，将水拉上木质部。水分子间的内聚力及其与木质部壁的附着力（毛细作用）有助于维持连续水柱。影响蒸腾速率的因素包括光照强度、温度、湿度和风速，可利用蒸腾计研究这些因素。

Translocation is an active process explained by the mass flow hypothesis. At the source, sucrose is actively loaded into the phloem sieve tubes, reducing water potential and causing water to enter by osmosis. This builds up hydrostatic pressure, driving the sap towards sinks where sucrose is unloaded. The companion cells provide ATP for the active loading.

转运是一个依赖能量的主动过程，可用压力流假说解释。在源端，蔗糖被主动装载到韧皮部筛管，降低水势，使水分通过渗透进入，从而建立静水压，驱动汁液流向库端，在那里蔗糖被卸载。伴胞为主动装载提供 ATP。

9. Transport in Mammals | 哺乳动物运输

The mammalian circulatory system is a closed, double circulation with blood passing through the heart twice in one complete circuit. You need to describe the external and internal structure of the heart: four chambers (atria and ventricles), the septum, and associated blood vessels—vena cava, pulmonary artery, pulmonary vein, and aorta. The cardiac cycle involves atrial systole, ventricular systole, and diastole, coordinated by the sinoatrial node (SAN) and atrioventricular node (AVN).

哺乳动物循环系统是闭合的双循环，血液在一次完整循环中两次经过心脏。你需要描述心脏的外部与内部结构：四腔（心房与心室）、中隔，以及相关血管——腔静脉、肺动脉、肺静脉和主动脉。心动周期包括心房收缩期、心室收缩期和舒张期，由窦房结（SAN）和房室结（AVN）协调。

Blood consists of plasma, red blood cells (erythrocytes), white blood cells (leucocytes), and platelets. Erythrocytes lack a nucleus and are biconcave, containing haemoglobin for oxygen transport. The oxygen dissociation curve illustrates how haemoglobin’s affinity for oxygen changes with partial pressure; the sigmoid shape is due to cooperative binding. The Bohr effect describes how increased carbon dioxide concentration lowers pH, shifting the curve to the right and promoting oxygen unloading in respiring tissues.

血液由血浆、红细胞、白细胞和血小板组成。红细胞无核、双凹形，含血红蛋白用于运载氧气。氧解离曲线显示了血红蛋白对氧的亲和力如何随分压变化；S 形曲线源于协同结合。波尔效应说明，二氧化碳浓度升高导致 pH 下降，使曲线右移，促进氧气在呼吸组织处释放。

Fetal haemoglobin has a higher affinity for oxygen than adult haemoglobin, enabling the fetus to obtain oxygen from the maternal blood across the placenta. Carbon dioxide is transported in the blood as hydrogencarbonate ions (HCO₃⁻), dissolved, and bound to haemoglobin as carbaminohaemoglobin.

胎儿血红蛋白与氧的亲和力高于成人血红蛋白，使胎儿能从母体血液经胎盘获取氧气。二氧化碳在血液中以碳酸氢根离子（HCO₃⁻）、溶解形式和与血红蛋白结合的氨基甲酸血红蛋白的形式运输。

10. Gas Exchange and Smoking | 气体交换与吸烟

The human gas exchange system includes the trachea, bronchi, bronchioles, and alveoli. The trachea and bronchi are supported by incomplete rings of cartilage, lined with ciliated epithelium and goblet cells that secrete mucus to trap pathogens and debris. Alveoli are the site of gas exchange; they are thin-walled, surrounded by an extensive capillary network, creating a short diffusion distance and large surface area.

人体气体交换系统包括气管、支气管、细支气管和肺泡。气管和支气管由不完整的软骨环支撑，内衬纤毛上皮和分泌黏液以捕捉病原体与颗粒物的杯状细胞。肺泡是气体交换的场所；它们壁薄，周围有丰富毛细血管网，形成了短的扩散距离与巨大的表面积。

The mechanism of ventilation involves the diaphragm and intercostal muscles. During inspiration, the external intercostal muscles contract, raising the ribcage, and the diaphragm contracts and flattens; this increases thoracic volume, decreasing pressure, so air rushes in. Expiration is largely passive at rest but becomes active during exercise when internal intercostal muscles and abdominal muscles contract.

通气机制涉及膈肌和肋间肌。吸气时，外肋间肌收缩提升胸廓，膈肌收缩变平；胸腔容积增大，压力降低，空气涌入。安静时呼气主要是被动过程，但运动时转为主动，内肋间肌和腹肌收缩。

Smoking causes serious health problems. Tar damages cilia, leading to mucus accumulation and chronic bronchitis; carcinogens in tobacco smoke can cause lung cancer; nicotine increases heart rate and blood pressure; carbon monoxide binds irreversibly to haemoglobin, reducing oxygen-carrying capacity. Emphysema is the breakdown of alveolar walls, reducing surface area for gas exchange. The syllabus requires understanding of these effects and epidemiological evidence linking smoking to disease.

吸烟导致严重的健康问题。焦油损伤纤毛，引起黏液堆积和慢性支气管炎；烟雾中的致癌物可导致肺癌；尼古丁使心率加快、血压升高；一氧化碳与血红蛋白不可逆结合，降低携氧能力。肺气肿是肺泡壁破裂，减少了气体交换面积。大纲要求理解这些影响以及将吸烟与疾病联系起来的流行病学证据。

11. Infectious Disease | 传染病

Infectious diseases are caused by pathogens: bacteria, viruses, fungi, and protoctists. Transmission can be direct (contact, droplet infection) or indirect (through vectors, contaminated food or water). You must study three case studies in depth: cholera, malaria, and tuberculosis (TB).

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AS CAIE Biology: Full Syllabus Breakdown | AS CAIE 生物：课程大纲全面解析