AS Edexcel Biology: Core Topics Overview | AS Edexcel 生物：核心知识点梳理

📚 AS Edexcel Biology: Core Topics Overview | AS Edexcel 生物：核心知识点梳理

This article provides a concise yet comprehensive overview of the core topics covered in the AS Edexcel Biology specification. It is designed to help you revise the fundamental concepts, from biological molecules to biodiversity, using clear explanations and examples that mirror exam requirements. Each section is presented in both English and Chinese to support bilingual learners.

本文概述了AS Edexcel 生物学课程涉及的核心主题，从生物分子到生物多样性，以清晰的结构和紧扣考点的示例帮助你高效复习。每个知识点均以中英双语配对呈现，方便双语学习者对照理解。

1. Biological Molecules | 生物分子

Biological macromolecules are polymers formed from smaller monomers through condensation reactions, which release water. Examples include polysaccharides from monosaccharides, proteins from amino acids, and nucleic acids from nucleotides. Hydrolysis is the reverse process that breaks these polymers back into monomers using water.

生物大分子是由小分子单体通过缩合反应形成的聚合物，同时释放水分子。例如，多糖由单糖缩合而成，蛋白质由氨基酸缩合而成，核酸由核苷酸缩合而成。水解则是利用水将聚合物分解为单体的逆过程。

Glucose is a hexose monosaccharide with the formula C₆H₁₂O₆. α‑glucose and β‑glucose differ in the orientation of the –OH group on carbon 1. Starch (a mixture of amylose and amylopectin) and glycogen are energy storage polysaccharides made of α‑glucose, while cellulose is a structural polysaccharide composed of β‑glucose chains held together by hydrogen bonds.

葡萄糖是一种己糖单糖，分子式为C₆H₁₂O₆。α‑葡萄糖和β‑葡萄糖的区别在于1号碳上羟基的朝向。淀粉（直链淀粉与支链淀粉的混合物）和糖原是由α‑葡萄糖组成的储能多糖，而纤维素是由β‑葡萄糖构成的结构多糖，平行链之间由氢键连接。

Triglycerides are formed by esterification of one glycerol molecule with three fatty acids; they are hydrophobic and serve for energy storage and insulation. Phospholipids have a hydrophilic phosphate head and two hydrophobic fatty acid tails, making them the fundamental building blocks of cell membranes as they spontaneously form a bilayer.

甘油三酯由一个甘油分子与三个脂肪酸酯化形成，具疏水性，用于能量储存和保温。磷脂含有一个亲水的磷酸头基和两条疏水的脂肪酸尾，能自发形成双分子层，是细胞膜的基本结构单元。

Proteins are polymers of amino acids linked by peptide bonds. Their primary structure is the linear sequence of amino acids; secondary structure includes α‑helices and β‑pleated sheets stabilised by hydrogen bonds; tertiary structure is the overall 3D folding maintained by hydrogen bonds, ionic bonds, disulfide bridges, and hydrophobic interactions; quaternary structure arises when multiple polypeptide chains associate.

蛋白质是由氨基酸通过肽键连接而成的聚合物。一级结构是氨基酸的线性序列；二级结构包括由氢键稳定的α‑螺旋和β‑折叠；三级结构是由氢键、离子键、二硫键和疏水相互作用维持的三维折叠形状；四级结构则涉及多条多肽链的聚合。

---

2. Enzymes | 酶

Enzymes are globular proteins that act as biological catalysts, lowering the activation energy of a reaction. The substrate fits into the enzyme’s active site, forming an enzyme–substrate complex. The induced fit model proposes that the active site changes shape slightly to accommodate the substrate, putting strain on chemical bonds and facilitating the reaction.

酶是球状蛋白质，作为生物催化剂降低反应的活化能。底物进入酶的活性位点，形成酶–底物复合物。诱导契合模型认为，活性位点会轻微改变形状以容纳底物，对化学键施加应力，从而促进反应。

Enzyme activity increases with temperature up to an optimum (around 37 °C for many human enzymes), but above this the enzyme denatures as hydrogen bonds break. Each enzyme has an optimum pH; deviations alter the charge on active‑site residues, reducing activity. Raising substrate concentration increases the rate of reaction until all active sites are saturated (Vₘₐₓ is reached). Competitive inhibitors bind to the active site, whereas non‑competitive inhibitors bind elsewhere, changing the shape of the active site.

温度升高时酶活性上升，至最适温度（人体多数酶约为37 °C）后，氢键断裂导致酶变性。酶有其最适pH，偏离时活性位点残基的电荷改变，活性下降。增加底物浓度可提高反应速率，直至所有活性位点饱和，达到最大速率Vₘₐₓ。竞争性抑制剂占据活性位点，非竞争性抑制剂则结合于其他位置，改变活性位点的形状。

---

3. Cell Structure and Function | 细胞结构与功能

Eukaryotic cells contain membrane‑bound organelles. The nucleus stores DNA and controls cellular activities. Mitochondria are the site of aerobic respiration. The rough endoplasmic reticulum (RER) has ribosomes for protein synthesis and transport, while the smooth ER is involved in lipid synthesis. The Golgi apparatus modifies and packages proteins into vesicles. Lysosomes contain digestive enzymes, ribosomes assemble proteins, and chloroplasts (in plants) carry out photosynthesis. The cytoskeleton provides shape and enables movement.

真核细胞含有膜包被的细胞器。细胞核储存DNA并调控细胞活动。线粒体是有氧呼吸的场所。粗面内质网表面附着核糖体，负责蛋白质的合成与运输；光面内质网参与脂质合成。高尔基体修饰蛋白质并将其包裹进囊泡。溶酶体含有消化酶，核糖体组装蛋白质，叶绿体（植物细胞）进行光合作用。细胞骨架提供形态支撑并协助运动。

Prokaryotic cells, such as bacteria, are smaller and lack a true nucleus and membrane‑bound organelles. Their DNA is a circular chromosome lying free in the cytoplasm. They possess 70S ribosomes, a cell wall made of peptidoglycan, and may have a capsule, flagellum, and small circular plasmids.

原核细胞（如细菌）体积较小，没有真正的细胞核和膜结合细胞器。其DNA为环状染色体，游离于细胞质中。它们拥有70S核糖体、肽聚糖构成的细胞壁，可能还有荚膜、鞭毛和小型环状质粒。

---

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

The fluid mosaic model describes the cell membrane as a phospholipid bilayer in which proteins are embedded. Phospholipids can move laterally, giving the membrane fluidity. Transport proteins include channel proteins and carrier proteins; glycoproteins serve in cell recognition. Cholesterol molecules are interspersed to regulate membrane fluidity.

流动镶嵌模型将细胞膜描述为嵌入蛋白质的磷脂双分子层。磷脂可以侧向移动，使膜具有流动性。运输蛋白包括通道蛋白和载体蛋白；糖蛋白参与细胞识别。胆固醇分子散布其间，调节膜的流动性。

Passive transport does not require ATP. Simple diffusion is the net movement of small, non‑polar molecules down a concentration gradient. Facilitated diffusion uses channel or carrier proteins for polar or large molecules. Osmosis is the net diffusion of water through a selectively permeable membrane from a region of higher water potential to a region of lower water potential. Active transport uses carrier proteins and ATP to move substances against their concentration gradient. Bulk transport is achieved by endocytosis and exocytosis via vesicles.

被动运输不需要ATP。简单扩散是小分子非极性物质顺浓度梯度的净移动。易化扩散利用通道蛋白或载体蛋白运输极性分子或大分子。渗透是水通过选择性通透膜从水势较高的区域向水势较低区域净扩散的过程。主动运输利用载体蛋白和ATP逆浓度梯度运输物质。胞吞和胞吐通过囊泡进行批量运输。

---

5. Nucleic Acids and DNA Replication | 核酸与DNA复制

DNA is a double helix made of two antiparallel polynucleotide strands. Each nucleotide consists of deoxyribose sugar, a phosphate group, and a nitrogenous base (adenine, thymine, guanine, or cytosine). Adenine pairs with thymine through two hydrogen bonds, and cytosine pairs with guanine through three hydrogen bonds. The strands are held together by hydrogen bonds between bases, while the sugar–phosphate backbone is linked by phosphodiester bonds.

DNA为双螺旋结构，由两条反向平行的多核苷酸链组成。每个核苷酸包含脱氧核糖、一个磷酸基团和一个含氮碱基（腺嘌呤、胸腺嘧啶、鸟嘌呤或胞嘧啶）。腺嘌呤与胸腺嘧啶通过两个氢键配对，胞嘧啶与鸟嘌呤通过三个氢键配对。碱基之间的氢键维持双链结构，而糖–磷酸骨架则由磷酸二酯键连接。

DNA replication is semi‑conservative: each original strand acts as a template for a new complementary strand. DNA helicase unwinds the double helix. DNA polymerase adds free nucleotides to the template in the 5′ to 3′ direction, forming phosphodiester bonds. The leading strand is synthesised continuously, whereas the lagging strand is synthesised in short Okazaki fragments, which are later joined by DNA ligase.

DNA复制是半保留的：每条原始链作为模板指导新的互补链合成。DNA解旋酶解开双螺旋。DNA聚合酶沿5′到3′方向在模板上添加游离核苷酸，形成磷酸二酯键。前导链连续合成，后随链则合成不连续的冈崎片段，随后由DNA连接酶连接起来。

---

6. Protein Synthesis | 蛋白质合成

Transcription occurs in the nucleus. The gene’s DNA unwinds, and RNA polymerase synthesises a complementary messenger RNA (mRNA) strand using the template strand, with uracil replacing thymine. The pre‑mRNA is modified (e.g., splicing) in eukaryotic cells before it leaves the nucleus.

转录发生在细胞核中。基因的DNA解旋，RNA聚合酶以模板链为模板合成互补的信使RNA（mRNA），其中尿嘧啶代替胸腺嘧啶。真核细胞中，前体mRNA在离开细胞核前会进行修饰（如剪接）。

Translation takes place on ribosomes in the cytoplasm. Transfer RNA (tRNA) molecules bring specific amino acids to the ribosome; their anticodon base‑pairs with the mRNA codon. The ribosome moves along the mRNA, and peptide bonds form between adjacent amino acids, elongating the polypeptide chain. Translation continues until a stop codon is reached, releasing the completed polypeptide.

翻译在细胞质中的核糖体上进行。转运RNA（tRNA）将特定氨基酸带到核糖体，其反密码子与mRNA的密码子配对。核糖体沿mRNA滑动，相邻氨基酸之间形成肽键，延长多肽链。翻译持续进行，直至遇到终止密码子，完整多肽链被释放。

---

7. Cell Cycle and Mitosis | 细胞周期与有丝分裂

The cell cycle consists of interphase (G₁, S, G₂) and the mitotic phase (mitosis and cytokinesis). DNA replicates during S phase. Mitosis is the division of the nucleus producing two genetically identical daughter nuclei. Its stages are prophase (chromosomes condense, spindle forms), metaphase (chromosomes align at the equator), anaphase (sister chromatids are pulled to opposite poles), and telophase (nuclear envelopes reform). Cytokinesis then divides the cytoplasm.

细胞周期包括间期（G₁、S、G₂）和分裂期（有丝分裂及胞质分裂）。S期进行DNA复制。有丝分裂是细胞核的分裂，产生两个遗传上相同的子核。其各阶段为：前期（染色体凝集，纺锤体形成）、中期（染色体排列在赤道板）、后期（姐妹染色单体被拉向两极）和末期（核膜重新形成）。随后胞质分裂将细胞质分开。

Cancer results from uncontrolled cell division caused by mutations in proto‑oncogenes or tumour suppressor genes. Oncogenes drive excessive proliferation, while loss of tumour suppressor function removes critical checkpoints in the cell cycle.

癌症由原癌基因或抑癌基因突变引起的细胞分裂失控所致。原癌基因促使细胞过度增殖，抑癌基因功能丧失则移除了细胞周期中关键的检查点。

---

8. Gas Exchange and Smoking | 气体交换与吸烟

The human gas exchange system includes the trachea, bronchi, bronchioles, and numerous alveoli. Alveoli have a large surface area, thin walls (one cell thick), and a dense capillary network, facilitating efficient diffusion. Oxygen diffuses from alveolar air into the blood, and carbon dioxide diffuses in the opposite direction. Breathing involves inspiration (diaphragm contracts, external intercostal muscles raise the ribs) and expiration (diaphragm relaxes; passive during quiet breathing).

人体气体交换系统包括气管、支气管、细支气管和大量肺泡。肺泡表面积大，壁极薄（单层细胞），且毛细血管丰富，有利于高效扩散。氧气从肺泡气扩散进入血液，二氧化碳反向扩散。呼吸运动包括吸气（膈肌收缩，外肋间肌提升肋骨）和呼气（膈肌松弛；安静呼吸时被动进行）。

Cigarette smoke contains tar (a carcinogen that also paralyses cilia), nicotine (an addictive substance that increases heart rate), and carbon monoxide (binds to haemoglobin, reducing the blood’s oxygen‑carrying capacity). Smoking is linked to chronic bronchitis, emphysema, lung cancer, and cardiovascular diseases.

香烟烟雾中含有焦油（致癌物，还可使纤毛瘫痪）、尼古丁（成瘾性物质，能加快心率）和一氧化碳（与血红蛋白结合，降低血液携氧能力）。吸烟与慢性支气管炎、肺气肿、肺癌以及心血管疾病密切相关。

---

9. Circulatory System | 循环系统

Mammals possess a double circulatory system. The heart has four chambers: right atrium, right ventricle, left atrium, and left ventricle. Blood follows the pathway: vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta. Valves prevent backflow. The cardiac cycle consists of atrial systole, ventricular systole, and diastole.

哺乳动物拥有双循环系统。心脏有四个

Published by TutorHao | AS Biology Revision Series | aleveler.com

更多咨询请联系16621398022（同微信）