Cambridge A-Level Biology: Contents and Syllabus Overview | 剑桥A-Level生物：考纲内容总览

📚 Cambridge A-Level Biology: Contents and Syllabus Overview | 剑桥A-Level生物：考纲内容总览

The Cambridge International AS and A Level Biology (9700) syllabus builds understanding from molecular and cellular biology to whole-organism physiology and ecosystems. This contents guide summarises the main topics assessed across the AS and A2 components, helping learners plan their revision strategically.

剑桥国际 AS 和 A Level 生物（9700）大纲从分子与细胞生物学逐步深入到整体生理学和生态系统。本内容指南总结了 AS 和 A2 部分考查的主要主题，帮助学习者策略性地规划复习。

1. Cell Structure | 细胞结构

Cell structure is the foundation of A-Level Biology. Learners compare eukaryotic and prokaryotic cells, identify organelles from electron micrographs, and explain how cell ultrastructure relates to function.

细胞结构是 A-Level 生物的基础。学习者比较真核细胞和原核细胞，从电子显微照片中识别细胞器，并解释细胞超微结构如何与功能相关。

Magnification and size calculations are essential practical skills. The relationship between actual size, image size and magnification is given below.

放大率和尺寸计算是必备的实验技能。实际尺寸、图像尺寸和放大率之间的关系如下。

magnification = image size ÷ actual size

Organelle | 细胞器	Key function | 主要功能
Nucleus | 细胞核	Stores genetic information | 储存遗传信息
Mitochondrion | 线粒体	Site of aerobic respiration | 有氧呼吸场所
Chloroplast | 叶绿体	Site of photosynthesis | 光合作用场所
Ribosome | 核糖体	Protein synthesis | 蛋白质合成

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2. Biological Molecules | 生物分子

Biological molecules are built from monomer units. Carbohydrates, proteins and lipids are assessed for both structure and function, while nucleic acids are examined in relation to information storage and protein synthesis.

生物分子由单体单元构建而成。碳水化合物、蛋白质和脂质考查结构和功能，而核酸则结合信息储存和蛋白质合成进行考查。

Common food tests include Benedict’s test for reducing sugars, iodine solution for starch, the biuret test for proteins and the ethanol emulsion test for lipids.

常见的食物检测包括还原糖的本尼迪克特试验、淀粉的碘液试验、蛋白质的双缩脲试验和脂质的乙醇乳化试验。

• Glycosidic bonds form between monosaccharides to make disaccharides and polysaccharides. | 单糖之间形成糖苷键，构成二糖和多糖。
• Peptide bonds link amino acids into polypeptide chains. | 肽键将氨基酸连接成多肽链。
• Ester bonds join fatty acids and glycerol in triglycerides. | 酯键在甘油三酯中连接脂肪酸和甘油。

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3. Enzymes | 酶

Enzymes are globular proteins that act as biological catalysts. The induced-fit model explains how the active site changes shape to stabilise the transition state and lower activation energy.

酶是作为生物催化剂的球状蛋白质。诱导契合模型解释了活性位点如何改变形状以稳定过渡态并降低活化能。

Temperature, pH, substrate concentration and enzyme concentration alter reaction rates. Denaturation is the irreversible loss of three-dimensional structure at extreme temperatures or pH values.

温度、pH、底物浓度和酶浓度会改变反应速率。变性是在极端温度或 pH 下三维结构的不可逆丧失。

Competitive inhibitors compete for the active site, while non-competitive inhibitors bind elsewhere and change the active site shape. Both affect Vmax and Km differently.

竞争性抑制剂争夺活性位点，而非竞争性抑制剂结合在其他部位并改变活性位点形状。两者对 Vmax 和 Km 的影响不同。

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4. Cell Membranes and Transport | 细胞膜与运输

The fluid mosaic model describes cell membranes as phospholipid bilayers with embedded proteins, cholesterol and glycoproteins. Membrane fluidity and selective permeability are key concepts.

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、胆固醇和糖蛋白。膜流动性和选择透过性是关键概念。

Simple diffusion and facilitated diffusion are passive processes, while active transport uses ATP to move substances against their concentration gradient. Osmosis is the net movement of water from a region of higher water potential to lower water potential through a partially permeable membrane.

简单扩散和易化扩散是被动过程，而主动运输使用 ATP 逆浓度梯度运输物质。渗透是水通过部分通透膜从水势较高的区域向水势较低区域的净移动。

Endocytosis and exocytosis allow bulk transport of large molecules across the membrane using vesicles.

胞吞作用和胞吐作用通过囊泡实现大分子跨膜的批量运输。

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5. Cell Division and Nucleic Acids | 细胞分裂与核酸

Mitosis produces genetically identical diploid daughter cells for growth and repair. The cell cycle includes interphase, prophase, metaphase, anaphase and telophase, followed by cytokinesis.

有丝分裂产生遗传上相同的二倍体子细胞，用于生长和修复。细胞周期包括间期、前期、中期、后期和末期，随后是胞质分裂。

DNA replication is semi-conservative: each new double helix contains one original strand and one newly synthesised strand. Transcription produces mRNA from DNA, and translation uses tRNA and ribosomes to assemble amino acids into polypeptides.

DNA 复制是半保留的：每个新的双螺旋含有一条原始链和一条新合成的链。转录从 DNA 生成 mRNA，翻译利用 tRNA 和核糖体将氨基酸组装成多肽。

The genetic code is degenerate, universal and non-overlapping. Mutations can affect protein structure and function.

遗传密码具有简并性、普遍性和非重叠性。突变可以影响蛋白质的结构和功能。

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6. Transport in Animals and Plants | 动植物运输系统

In mammals, the closed double circulatory system includes the heart, arteries, veins and capillaries. The cardiac cycle coordinates atrial and ventricular contraction, and haemoglobin binds oxygen cooperatively to transport it from lungs to tissues.

在哺乳动物中，闭合式双循环系统包括心脏、动脉、静脉和毛细血管。心动周期协调心房和心室收缩，血红蛋白协同结合氧，将氧从肺部运输到组织。

In plants, xylem transports water and mineral ions upwards through transpiration pull. Phloem translocates sucrose and amino acids from sources to sinks via the mass flow hypothesis.

在植物中，木质部通过蒸腾拉力向上运输水和矿质离子。韧皮部通过压力流假说将蔗糖和氨基酸从源运输到库。

• Cardiac output = stroke volume × heart rate | 心输出量 = 每搏输出量 × 心率
• Transpiration is affected by light, temperature, humidity and wind | 蒸腾作用受光照、温度、湿度和风的影响

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7. Gas Exchange and Respiration | 气体交换与呼吸

Gas exchange surfaces are thin, moist and have a large surface area relative to volume. Mammalian alveoli, fish gills with countercurrent flow, and plant stomatal pores all maximise diffusion efficiency.

气体交换表面薄、湿润且具有较大的相对表面积。哺乳动物肺泡、具有逆流交换的鱼鳃以及植物气孔都使扩散效率最大化。

Cellular respiration releases energy from glucose. Aerobic respiration includes glycolysis, the link reaction, the Krebs cycle and oxidative phosphorylation.

细胞呼吸从葡萄糖中释放能量。有氧呼吸包括糖酵解、连接反应、克雷布斯循环和氧化磷酸化。

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)

Anaerobic respiration in mammals produces lactate, while yeast produces ethanol and carbon dioxide.

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