📚 KS3 Edexcel Biology Formula & Theorem Quick Reference Handbook | KS3 Edexcel 生物：公式定理速查手册
Welcome to the ultimate quick-reference guide for the KS3 Edexcel Biology course. This handbook brings together the most important formulas, equations, and foundational theorems that underpin topics ranging from cell structure to inheritance. Use these pages to reinforce your understanding and to answer questions with confidence.
欢迎查阅这份为 KS3 Edexcel 生物课程量身打造的终极速查手册。这里汇集了从细胞结构到遗传等主题中的关键公式、方程式和基本定理，帮助你巩固理解，自信应对各类考题。
1. Cell Theory | 细胞学说
All living organisms are composed of one or more cells, and the cell is the basic structural and functional unit of life.
所有生物体都由一个或多个细胞组成，细胞是生命的基本结构和功能单位。
Cells arise only from pre-existing cells through division, not from non-living matter.
细胞只能通过分裂从已存在的细胞产生，而非来自非生命物质。
The chemical reactions necessary for life occur inside cells, coordinating to maintain homeostasis.
维持生命所需的化学反应都在细胞内进行，共同协作以维持稳态。
2. Microscopy Formula | 显微镜公式
The relationship between magnification, image size and actual size of a specimen is given by a fundamental formula.
放大倍数、图像尺寸与标本实际大小之间的关系由一个基本公式给出。
Magnification = Image size ÷ Actual size
M = I ÷ A
To calculate actual size, rearrange the formula: Actual size = Image size ÷ Magnification.
要计算实际大小，可将公式变形：实际尺寸 = 图像尺寸 ÷ 放大倍数。
Ensure all measurements are in the same unit. Commonly you must convert millimetres to micrometres: 1 mm = 1000 µm.
确保所有测量单位统一。通常需要将毫米转换为微米：1 毫米 = 1000 微米。
3. Photosynthesis Equation | 光合作用方程式
Photosynthesis is the process by which green plants and some other organisms use light energy to convert carbon dioxide and water into glucose and oxygen.
光合作用是绿色植物和某些其他生物利用光能将二氧化碳和水转化为葡萄糖和氧气的过程。
Carbon dioxide + Water → Glucose + Oxygen
6CO&sb2; + 6H&sb2;O → C&sb6;H&sb1;&sb2;O&sb6; + 6O&sb2;
This reaction is endothermic, meaning it absorbs light energy trapped by chlorophyll in chloroplasts.
该反应是吸热反应，即它吸收被叶绿体中叶绿素捕获的光能。
Leaves are adapted to maximise photosynthesis with a large surface area, many chloroplasts, and stomata for gas exchange.
叶片通过较大的表面积、大量叶绿体以及用于气体交换的气孔来最大限度地进行光合作用。
4. Aerobic Respiration Equation | 有氧呼吸方程式
Aerobic respiration is the process that releases energy from glucose in the presence of oxygen, occurring continuously in the mitochondria of most cells.
有氧呼吸是在有氧条件下从葡萄糖中释放能量的过程，在大多数细胞的线粒体中持续进行。
Glucose + Oxygen → Carbon dioxide + Water (+ energy transferred to ATP)
C&sb6;H&sb1;&sb2;O&sb6; + 6O&sb2; → 6CO&sb2; + 6H&sb2;O
Aerobic respiration is exothermic, releasing energy that organisms use for movement, growth, and maintaining body temperature.
有氧呼吸是放热反应，释放的能量用于生物体的运动、生长和体温维持。
5. Anaerobic Respiration Equations | 无氧呼吸方程式
When oxygen is insufficient, cells can respire anaerobically, producing less energy and forming different waste products in animals and plants or fungi.
当氧气不足时，细胞可进行无氧呼吸，产生较少的能量，并在动物和植物或真菌中形成不同的废物。
In animals: Glucose → Lactic acid (+ some energy)
C&sb6;H&sb1;&sb2;O&sb6; → 2C&sb3;H&sb6;O&sb3;
In plants and yeast: Glucose → Ethanol + Carbon dioxide (+ some energy)
C&sb6;H&sb1;&sb2;O&sb6; → 2C&sb2;H&sb5;OH + 2CO&sb2;
In yeast, this process is called fermentation and is used in baking and brewing. The ethanol and carbon dioxide are the useful products.
在酵母中，这一过程称为发酵，用于烘焙和酿造。乙醇和二氧化碳是有用的产物。
An oxygen debt builds up in muscles when lactic acid accumulates; it is repaid by continued deep breathing after exercise.
当乳酸在肌肉中堆积时会形成氧债；运动后通过持续深呼吸来偿还。
6. Enzyme Action: Lock-and-Key Model | 酶作用：锁钥模型
Enzymes are biological catalysts that speed up chemical reactions without being used up. They are proteins with a specific active site.
酶是生物催化剂，能加快化学反应而自身不被消耗。它们是具有特定活性部位的蛋白质。
Enzyme (E) + Substrate (S) ⇄ Enzyme-substrate complex (ES) → Enzyme + Products (P)
The lock-and-key model states that the substrate fits precisely into the enzyme’s active site, like a key into a lock. Some modern descriptions refer to an induced-fit refinement.
锁钥模型认为，底物精确地嵌入酶的活性部位，就像钥匙插入锁孔。现代描述有时会提到诱导契合的微调。
Each enzyme works best at an optimum pH and temperature. High temperatures denature the enzyme, changing the shape of its active site permanently.
每种酶在最适 pH 和温度下活性最高。高温会使酶变性，永久改变其活性部位的形状。
7. Diffusion, Osmosis and Active Transport | 扩散、渗透与主动运输
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down the concentration gradient. It is a passive process.
扩散是粒子从高浓度区域沿浓度梯度向低浓度区域的净移动，是一种被动过程。
Osmosis is specifically the diffusion of water molecules through a partially permeable membrane from a dilute solution to a more concentrated one.
渗透专指水分子通过半透膜从稀溶液向浓溶液的扩散。
Active transport requires energy (ATP) to move substances against the concentration gradient, from low to high concentration, using carrier proteins.
主动运输需要能量（ATP），利用载体蛋白逆浓度梯度将物质从低浓度区域运往高浓度区域。
Rate of diffusion ∝ (Surface area × Concentration gradient) ÷ Diffusion distance
This proportionality helps explain why structures like alveoli and villi have large surface areas, steep gradients, and thin walls.
这一比例关系可以解释为什么肺泡和小肠绒毛等结构具有较大的表面积、陡的浓度梯度和薄的壁层。
8. Food Chains and Energy Transfer | 食物链与能量传递
Energy enters food chains through producers, usually photosynthetic organisms. At each trophic level, only a fraction of the energy is passed on.
能量通过生产者（通常是光合生物）进入食物链。在每个营养级，只有一小部分能量被传递下去。
Approximately 10% of the energy stored in one trophic level becomes stored in the next; the rest is lost as heat, movement, waste or undigested material.
大约只有 10% 储存在某一营养级的能量会储存在下一级；其余以热、运动、废物或未消化物质的形式散失。
Energy efficiency (%) = (Energy transferred to next level ÷ Energy available at current level) × 100
Pyramids of numbers, biomass and energy are used to represent feeding relationships, with pyramids of energy always being upright.
数量金字塔、生物量金字塔和能量金字塔用于表示取食关系，能量金字塔总是呈正金字塔形。
9. Inheritance: Mendel’s Principles | 遗传原理：孟德尔定律
Gregor Mendel discovered that characteristics are determined by units called genes, which exist in different forms called alleles.
格雷戈尔·孟德尔发现性状由称为基因的单位决定，基因有不同的形式，称为等位基因。
Law of Segregation: The two alleles for each trait separate during gamete formation, so each gamete carries only one allele.
一对等位基因在配子形成时彼此分离，每个配子仅携带一个等位基因。
A dominant allele (e.g. T for tall) masks a recessive allele (t for short) when both are present. The phenotype is the observable characteristic.
当显性等位基因（如高茎 T）与隐性等位基因（矮茎 t）共存时，显性会掩盖隐性。表型是可观察的性状。
A Punnett square predicts genotype ratios from a monohybrid cross. Example: Tt × Tt yields offspring genotypes 1 TT : 2 Tt : 1 tt, and phenotypes 3 tall : 1 short.
庞纳特方格用于预测单基因杂交的基因型比率。例如 Tt × Tt 的后代基因型比为 1 TT : 2 Tt : 1 tt，表型比为 3 高 : 1 矮。
| T | t | |
| T | TT | Tt |
| t | Tt | tt |
10. Transpiration and Water Transport | 蒸腾作用与水分运输
Transpiration is the evaporation of water from the surfaces of leaves, mainly through stomata. It creates a pulling force that draws water up the xylem vessels.
蒸腾作用是水分从叶片表面（主要通过气孔）蒸发的过程。它产生拉力，将水分向上拉入木质部导管。
The cohesive and adhesive properties of water molecules maintain an unbroken column of water from roots to leaves.
水分子的内聚力和附着力维持了从根部到叶片不间断的水柱。
Factors increasing transpiration rate include higher temperature, increased air movement, lower humidity, and greater light intensity.
提高蒸腾速率的因素包括较高的温度、增强的空气流动、较低的湿度和更强的光照。
11. Key Chemical Transformations in the Carbon Cycle | 碳循环中的关键化学变化
The carbon cycle links photosynthesis, respiration, combustion, and decomposition through chemical equations you already know.
碳循环通过你已经学过的化学方程式将光合作用、呼吸作用、燃烧和分解作用联系起来。
Photosynthesis removes CO&sb2; from the atmosphere; respiration and combustion return it. Decomposition by microorganisms involves respiration of dead organic matter.
光合作用从大气中移除二氧化碳；呼吸作用和燃烧将其送回。微生物分解涉及对死亡有机物的呼吸作用。
Combustion of biomass: C&sb6;H&sb1;&sb2;O&sb6; + 6O&sb2; → 6CO&sb2; + 6H&sb2;O
The formation of fossil fuels locks carbon away for millions of years; burning them releases stored carbon rapidly, upsetting the natural balance.
化石燃料的形成将碳封存数百万年；燃烧它们会迅速释放储存的碳，打破自然平衡。
12. Digestive Reactions and Enzymatic Breakdown | 消化反应与酶促分解
Large insoluble food molecules must be broken down into smaller soluble ones by digestive enzymes. Each enzyme acts on a specific substrate.
大而不溶的食物分子必须被消化酶分解为较小的可溶性分子。每种酶作用于特定的底物。
Carbohydrates (starch) → Amylase → Maltose → Glucose
Proteins → Protease → Peptides → Amino acids
Lipids (fats) → Lipase → Glycerol + Fatty acids
These breakdown reactions are hydrolysis reactions, requiring water. The products are absorbed by diffusion or active transport in the small intestine.
这些分解反应是水解反应，需要水参与。产物在小肠通过扩散或主动运输被吸收。
Absorption occurs in the ileum where villi and microvilli greatly increase the surface area for efficient transport.
吸收发生在回肠，肠绒毛和微绒毛大大增加了表面积，以实现高效的转运。
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