📚 Core Knowledge Review for Year 12 CIE Biology | Year 12 CIE 生物核心知识点梳理
This article provides a comprehensive summary of the core topics covered in Year 12 CIE AS Biology (9700 syllabus). It is designed to help students consolidate key concepts, from cell structure and biological molecules to physiology and immunity. Each section pairs essential English explanations with Chinese translations to support bilingual learners.
本文全面梳理了 Year 12 CIE AS 生物 (9700 大纲) 的核心主题，旨在帮助学生巩固从细胞结构和生物分子到生理学与免疫等关键概念。每个部分均以英文解释配中文翻译，助力双语学习者。
1. Cell Structure | 细胞结构
Eukaryotic cells have membrane-bound organelles. The nucleus contains chromatin (DNA and histones) and a nucleolus. Mitochondria are the sites of aerobic respiration, with a double membrane and cristae. The rough endoplasmic reticulum (RER) has ribosomes for protein synthesis, while the smooth ER synthesises lipids. The Golgi apparatus modifies and packages proteins for secretion. Plant cells also have chloroplasts for photosynthesis, a large vacuole, and a cellulose cell wall.
真核细胞具有膜包被的细胞器。细胞核含有染色质 (DNA 和组蛋白) 及核仁。线粒体是有氧呼吸的场所，具有双层膜和嵴。粗面内质网 (RER) 附着核糖体进行蛋白质合成，滑面内质网则合成脂质。高尔基体修饰和包装蛋白质以分泌。植物细胞还具有叶绿体用于光合作用、一个大液泡和纤维素细胞壁。
Prokaryotic cells lack a nucleus and membrane-bound organelles. They have a circular DNA molecule in the nucleoid region, 70S ribosomes, and a cell wall made of peptidoglycan. Some bacteria have a capsule, flagella, or plasmids.
原核细胞没有细胞核及膜包被的细胞器。它们在拟核区域含有一个环状 DNA 分子、70S 核糖体和由肽聚糖构成的细胞壁。有些细菌具有荚膜、鞭毛或质粒。
The magnification formula is:
Magnification = Image size / Actual size
放大倍数公式为：
放大倍数 = 图像尺寸 / 实际尺寸
Using an eyepiece graticule and stage micrometer allows measurement of specimens.
使用目镜测微尺和镜台测微尺可以测量实验样本。
2. Biological Molecules | 生物分子
Carbohydrates include monosaccharides (e.g., glucose, fructose), disaccharides (maltose, sucrose), and polysaccharides (starch, glycogen, cellulose). Glycosidic bonds form by condensation and break by hydrolysis. Starch is a plant storage polysaccharide made of amylose and amylopectin. Glycogen is a highly branched animal storage polysaccharide. Cellulose is a structural polysaccharide with β-1,4 glycosidic bonds, forming microfibrils.
碳水化合物包括单糖 (如葡萄糖、果糖)、二糖 (麦芽糖、蔗糖) 和多糖 (淀粉、糖原、纤维素)。糖苷键通过缩合反应形成，水解反应断裂。淀粉是植物储存多糖，由直链淀粉和支链淀粉组成。糖原是高度分支的动物储存多糖。纤维素是结构多糖，含有 β-1,4 糖苷键，形成微纤丝。
Lipids are triglycerides (fats and oils) composed of glycerol and three fatty acids joined by ester bonds. Phospholipids have a phosphate group, making them amphipathic — crucial for membranes. Lipids are energy stores, insulators, and solvent carriers.
脂质是甘油三酯 (脂肪和油)，由甘油和三个脂肪酸通过酯键连接而成。磷脂含有磷酸基团，使其具有两亲性，对生物膜至关重要。脂质可作为能量储存、绝缘体和溶剂载体。
Proteins are polymers of amino acids linked by peptide bonds. The primary structure is the sequence of amino acids; secondary structures are α-helices and β-pleated sheets formed by hydrogen bonds; tertiary structure is the overall 3D folding maintained by hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions; quaternary structure involves multiple polypeptide chains. The biuret test detects peptide bonds.
蛋白质是由氨基酸通过肽键连接而成的多聚体。一级结构是氨基酸序列；二级结构是由氢键形成的 α-螺旋和 β-折叠；三级结构是整体三维折叠，靠氢键、离子键、二硫键和疏水作用维持；四级结构涉及多条多肽链。双缩脲试验可检测肽键。
Water is a dipolar molecule, forming hydrogen bonds. Its properties — high specific heat capacity, high latent heat of vaporisation, cohesion, and solvent ability — are vital for life.
水是极性分子，能形成氢键。其性质——高比热容、高汽化潜热、内聚力及溶剂能力——对生命至关重要。
3. Enzymes | 酶
Enzymes are globular proteins that act as biological catalysts, lowering activation energy. The active site has a specific shape complementary to the substrate. The induced-fit model states that the active site moulds around the substrate. Factors affecting enzyme activity include temperature, pH, enzyme concentration, and substrate concentration. At the optimum temperature/pH, activity is maximal; extreme conditions denature the enzyme.
酶是球状蛋白，作为生物催化剂降低活化能。活性部位具有与底物互补的特定形状。诱导契合模型认为活性部位会围绕底物改变构象。影响酶活性的因素包括温度、pH、酶浓度和底物浓度。在最佳温度/pH 下活性最大；极端条件会使酶变性。
Michaelis-Menten kinetics describe the relationship between substrate concentration and rate of reaction. The Michaelis constant Kₘ indicates the substrate concentration at half Vmax; a low Kₘ reflects high affinity. Competitive inhibition increases Kₘ but Vmax unchanged; non-competitive inhibition lowers Vmax but Kₘ unchanged.
米氏动力学描述底物浓度与反应速率的关系。米氏常数 Kₘ 表示半最大反应速率时的底物浓度；低 Kₘ 反映高亲和力。竞争性抑制使 Kₘ 增大而 Vmax 不变；非竞争性抑制降低 Vmax 而 Kₘ 不变。
Immobilised enzymes are attached to inert matrices, allowing reuse and easy separation from products. They are used in biosensors and industrial processes like lactose-free milk production.
固定化酶附着在惰性基质上，可重复使用并易于从产物中分离。常用于生物传感器及工业过程，如无乳糖牛奶的生产。
4. Cell Membranes and Transport | 细胞膜与运输
The fluid mosaic model describes membranes as a phospholipid bilayer with embedded proteins, cholesterol (in animals), and glycoproteins. Phospholipids have hydrophilic heads and hydrophobic tails, forming a barrier to water-soluble molecules. Proteins function as channels, carriers, receptors, and enzymes.
流动镶嵌模型将膜描述为磷脂双分子层，其中嵌入蛋白质、胆固醇 (动物细胞) 和糖蛋白。磷脂具有亲水头部和疏水尾部，形成水溶性分子的屏障。蛋白质具有通道、载体、受体和酶的功能。
sis is the net movement of water through a partially permeable membrane from higher to lower water potential. Water potential Ψ = solute potential Ψₛ + pressure potential Ψₚ.
被动运输包括扩散 (沿浓度梯度移动) 和借助通道蛋白或载体蛋白的易化扩散。渗透是水通过部分透性膜从高水势向低水势的净移动。水势 Ψ = 溶质势 Ψₛ + 压力势 Ψₚ。
Active transport uses ATP and carrier proteins to move substances against their concentration gradient. Endocytosis and exocytosis are bulk transport processes involving vesicle formation and fusion with the membrane.
主动运输利用 ATP 和载体蛋白逆浓度梯度运送物质。胞吞和胞吐是涉及囊泡形成及与膜融合的批量运输过程。
5. The Cell Cycle and Mitosis | 细胞周期与有丝分裂
The cell cycle consists of interphase (G₁, S, G₂) and mitotic phase (mitosis and cytokinesis). During S phase, DNA replicates. Mitosis produces two genetically identical daughter nuclei for growth, repair, and asexual reproduction. The stages are prophase (chromosomes condense, nuclear envelope breaks down), metaphase (chromosomes align at the equator), anaphase (sister chromatids separate to poles
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