📚 Year 8 Edexcel Biology: Formula and Principles Quick Reference Handbook | Year 8 Edexcel 生物：公式定理速查手册
This quick reference handbook covers the essential formulas, equations and biological principles you need for Year 8 Edexcel Biology. It is designed for rapid revision, helping you recall key definitions, calculations and the core ideas that underpin topics from cells to respiration, genetics to gas exchange. Use it alongside your class notes to test yourself and build confidence before assessments.
这本速查手册涵盖了 Edexcel 爱德思 Year 8 生物课程中必须掌握的公式、方程式和生物学原理。手册专为快速复习设计，帮助你回忆关键定义、计算方式以及支撑细胞、呼吸、遗传与气体交换等主题的核心概念。与课堂笔记一起使用，在评估前自测并建立信心。
1. Magnification Formula | 放大倍率公式
Magnification describes how many times larger an image appears compared to the specimen’s actual size. The formula is: Magnification = Image size ÷ Actual size. Always use the same units for both image and actual size—convert to millimetres or micrometres if necessary. Remember that the image size is measured from a drawing or micrograph, while the actual size is the real length of the object.
放大倍率表示图像比标本实际尺寸大多少倍。公式为：放大倍率 = 图像大小 ÷ 实际大小。图像和实际尺寸必须使用相同单位——必要时转换为毫米或微米。记住图像大小是从绘图或显微照片上测量的，而实际大小是物体的真实长度。
| Symbol / 符号 | Meaning / 含义 | Unit / 单位 |
|---|---|---|
| M | Magnification / 放大倍率 | No unit (times) / 无单位（倍） |
| I | Image size / 图像大小 | mm, μm / 毫米、微米 |
| A | Actual size / 实际大小 | mm, μm / 毫米、微米 |
2. Total Magnification of a Microscope | 显微镜总放大倍率
When using a compound light microscope, the total magnification is the product of the eyepiece lens magnification and the objective lens magnification. Knowing this helps you select the right combination to view cell structures clearly. For example, a 10x eyepiece with a 40x objective gives 400x total magnification.
使用复式光学显微镜时，总放大倍率是目镜放大倍率与物镜放大倍率的乘积。了解这一点有助于选择正确的组合来清晰观察细胞结构。例如，10x 目镜配合 40x 物镜可获得 400 倍的总放大倍率。
Total magnification = Eyepiece magnification × Objective magnification / 总放大倍率 = 目镜放大倍率 × 物镜放大倍率
3. Aerobic and Anaerobic Respiration Equations | 有氧呼吸与无氧呼吸方程式
Respiration is the process that releases energy from glucose. In aerobic respiration, oxygen is used and a large amount of energy is released. The word equation summarises the reactants and products: Glucose + Oxygen → Carbon dioxide + Water (+ Energy). The balanced chemical equation is: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O. This occurs in the mitochondria of cells.
呼吸作用是释放葡萄糖中能量的过程。在有氧呼吸中，需要氧气参与并释放大量能量。文字方程式概括了反应物与产物：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）。配平的化学方程式为：C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O。这一过程发生在细胞的线粒体中。
When oxygen is lacking, anaerobic respiration occurs. In animal cells and some bacteria, glucose is converted to lactic acid, releasing a small amount of energy. The word equation is: Glucose → Lactic acid (+ Energy). In yeast, anaerobic respiration produces ethanol and carbon dioxide: Glucose → Ethanol + Carbon dioxide (+ Energy). This is called fermentation.
当氧气不足时，发生无氧呼吸。在动物细胞和某些细菌中，葡萄糖转化为乳酸，释放少量能量。文字方程式为：葡萄糖 → 乳酸（+ 能量）。在酵母中，无氧呼吸产生乙醇和二氧化碳：葡萄糖 → 乙醇 + 二氧化碳（+ 能量），称为发酵。
4. Photosynthesis Equation | 光合作用方程式
Photosynthesis is the process by which green plants and algae convert light energy into chemical energy stored in glucose. Chlorophyll in chloroplasts traps sunlight. The overall word equation is: Carbon dioxide + Water → Glucose + Oxygen (in the presence of light and chlorophyll). The balanced chemical equation is: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂. This reaction is endothermic, meaning it absorbs energy from the environment.
光合作用是绿色植物和藻类将光能转化为储存在葡萄糖中的化学能的过程。叶绿体中的叶绿素捕捉太阳光。总文字方程式为：二氧化碳 + 水 → 葡萄糖 + 氧气（在光照和叶绿素存在下）。配平的化学方程式为：6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂。该反应是吸热反应，意味着它从环境中吸收能量。
5. Enzyme Activity: Lock and Key Model | 酶活性：锁钥模型
Enzymes are biological catalysts that speed up reactions without being used up. The lock and key model states that each enzyme’s active site has a specific shape that only fits a complementary substrate, much like a key fits a specific lock. When the substrate binds, an enzyme‑substrate complex forms, the reaction occurs, and products are released.
酶是生物催化剂，能加速化学反应而自身不被消耗。锁钥模型指出，每个酶的活性位点具有特定的形状，只匹配互补的底物，就像钥匙只能打开特定的锁。当底物结合时，形成酶‑底物复合物，反应发生，产物释放。
Temperature and pH are crucial. Each enzyme has an optimum temperature (around 37°C in humans) and an optimum pH (e.g. pepsin works best at pH 2, amylase around pH 7). High temperatures or extreme pH denature the enzyme, changing the shape of the active site permanently so the substrate can no longer fit. This is a key principle governing all enzyme‑controlled reactions.
温度和 pH 至关重要。每种酶都有最适温度（人体内约为 37°C）和最适 pH（例如胃蛋白酶在 pH 2 时活性最高，淀粉酶约为 pH 7）。高温或极端 pH 会使酶变性，永久改变活性位点的形状，使底物无法再结合。这是支配所有酶控反应的关键原理。
6. Factors Affecting Diffusion Rate | 影响扩散速率的因素
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration. The rate of diffusion can be increased by a steeper concentration gradient, higher temperature (particles have more kinetic energy), a larger surface area of the membrane, and a shorter diffusion distance. These factors can be related to Fick’s law in more advanced study, but the principle is: diffusion rate ∝ (surface area × concentration difference) ÷ diffusion distance.
扩散是粒子从高浓度区域向低浓度区域的净移动。提高扩散速率的因素包括：更陡的浓度梯度、更高的温度（粒子动能更大）、膜的表面积越大以及扩散距离越短。在更高阶的学习中，这些因素可用菲克定律描述，但基本原理是：扩散速率 ∝ （表面积 × 浓度差） ÷ 扩散距离。
Diffusion rate ∝ (Surface area × Concentration difference) ÷ Distance / 扩散速率 ∝ （表面积 × 浓度差） ÷ 距离
7. Osmosis: Water Movement | 渗透：水分移动
Osmosis is a special type of diffusion that involves water molecules moving across a partially permeable membrane. Water moves from a dilute solution (high water potential, low solute concentration) to a more concentrated solution (low water potential, high solute concentration) until equilibrium is reached. The principle is vital for understanding how plant roots absorb water and how animal cells maintain turgidity or crenation.
渗透是一种特殊的扩散，指水分子通过部分透性膜的运动。水从稀溶液（高水势、低溶质浓度）向较浓溶液（低水势、高溶质浓度）移动，直至达到平衡。这一原理对于理解植物根系如何吸水以及动物细胞如何保持膨压或皱缩至关重要。
8. Surface Area to Volume Ratio | 表面积与体积比
As an organism or cell increases in size, its surface area to volume ratio (SA:V) decreases. This ratio governs the efficiency of exchange of materials such as oxygen, nutrients and waste. A high SA:V allows rapid diffusion, which is why many single‑celled organisms can rely on simple diffusion, while larger multicellular organisms require specialised exchange surfaces (e.g. alveoli in lungs, villi in the small intestine) and transport systems.
随着生物体或细胞体积增大，其表面积与体积比（SA:V）减小。这一比率决定了氧气、营养物质和废物等物质交换的效率。高 SA:V 比值可实现快速扩散，这就是为什么许多单细胞生物可以依赖简单扩散，而较大的多细胞生物则需要特化的交换表面（如肺中的肺泡、小肠中的绒毛）和运输系统。
SA:V ratio = Surface area ÷ Volume / 表面积与体积比 = 表面积 ÷ 体积
For a cube of side length l, SA = 6l², V = l³, so SA:V = 6/l. As l increases, the ratio decreases. / 对于边长为 l 的立方体，表面积 = 6l²，体积 = l³，因此 SA:V = 6/l。l 增大时，比值减小。
9. Energy Content of Food (Calorimetry) | 食物能量含量（量热法）
The energy stored in food can be estimated by burning a sample and using the heat released to warm a known mass of water. The formula for calculating the energy transferred is: Energy (J) = mass of water (g) × 4.2 J/g°C × temperature rise (°C). The value 4.2 represents the specific heat capacity of water. This method allows comparison of the energy content in different foods per gram.
食物中储存的能量可以通过燃烧样品并用释放的热量加热已知质量的水来估算。计算能量转移的公式为：能量（J）= 水的质量（g）× 4.2 J/g°C × 温度上升（°C）。4.2 是水的比热容。该方法能比较不同食物每克所含的能量。
E = m × c × ΔT where c = 4.2 J/g°C for water / E = m × c × ΔT，其中水的 c = 4.2 J/g°C
10. Monohybrid Inheritance (Genetic Crosses) | 单基因遗传（杂交）
Inheritance of a characteristic controlled by a single gene can be predicted using a Punnett square. A dominant allele (represented by a capital letter, e.g. B) masks the effect of a recessive allele (lowercase, e.g. b). When two heterozygous parents (Bb × Bb) are crossed, the expected phenotype ratio in the offspring is 3 dominant : 1 recessive. The genotype ratio is 1 BB : 2 Bb : 1 bb. This 3:1 ratio is the fundamental principle of Mendelian monohybrid inheritance.
由单个基因控制的性状遗传可通过旁氏表（Punnett square）预测。显性等位基因（用大写字母表示，如 B）会掩盖隐性等位基因（小写，如 b）的效应。当两个杂合亲本杂交（Bb × Bb）时，后代预期表现型比例为 3 显性 : 1 隐性。基因型比例为 1 BB : 2 Bb : 1 bb。这个 3:1 的比例是孟德尔单因子杂交遗传的基本原理。
| Punnett Square / 旁氏表 | B (female/male) | b |
|---|---|---|
| B (other parent) | BB | Bb |
| b | Bb | bb |
11. Lung Volumes and Ventilation | 肺容量与通气
Breathing involves moving air into and out of the lungs. Tidal volume (TV) is the volume of air moved in or out during a normal breath. The ventilation rate (also called breathing rate) is the number of breaths per minute. Minute ventilation (pulmonary ventilation) is the total volume of air breathed per minute and is calculated using the formula below. This principle links structure (alveoli, diaphragm) to the efficiency of gas exchange.
呼吸涉及空气进出肺部。潮气量（TV）是每次正常呼吸时吸入或呼出的空气体积。通气频率（也称呼吸频率）是每分钟的呼吸次数。每分通气量（肺通气量）是每分钟呼吸的空气总体积，计算公式如下。该原理将结构（肺泡、膈肌）与气体交换效率联系起来。
Minute ventilation = Tidal volume × Breathing rate / 每分通气量 = 潮气量 × 呼吸频率
12. Active Transport Principle | 主动转运原理
Active transport is the movement of molecules or ions across a cell membrane from a region of lower concentration to a region of higher concentration—against the concentration gradient. This process requires energy from respiration (ATP) and carrier proteins. It is essential for absorbing mineral ions by root hair cells in plants and for glucose absorption in the human gut when concentrations are already high in the blood. Unlike diffusion and osmosis, active transport is not a passive process.
主动转运是分子或离子跨细胞膜从低浓度区域向高浓度区域的移动——逆浓度梯度进行。该过程需要呼吸作用提供的能量（ATP）和载体蛋白。它对于植物根毛细胞吸收矿质离子以及人体肠道中当血液已含高浓度葡萄糖时的葡萄糖吸收至关重要。与扩散和渗透不同，主动转运不是一个被动过程。
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