📚 Year 9 AQA Biology: Formulas & Theorems Quick Reference Handbook | 九年级 AQA 生物：公式定理速查手册
This handbook brings together every key formula, word equation and essential relationship you need to know for the AQA Year 9 Biology course. Use it to check your calculations, practise conversions and make sure you can apply each concept confidently in an exam.
本手册汇集了 AQA 九年级生物学课程中你必须掌握的每一个关键公式、文字方程式以及重要的数量关系。用来核对计算、练习单位换算，确保在考试中能自信地运用每一个概念。
1. Microscopy Formulas | 显微镜公式
Magnification describes how many times larger an image is compared to the real object. The basic formula is: magnification = image size ÷ actual size. Always check that both measurements are in the same unit before calculating.
放大倍数表示图像比实际物体大多少倍。基本公式为：放大倍数 = 图像尺寸 ÷ 实际尺寸。计算前务必确保两个测量值单位一致。
The total magnification of a light microscope is found by multiplying the magnifying power of the eyepiece lens by that of the objective lens: total magnification = eyepiece magnification × objective magnification.
光学显微镜的总放大倍数可通过目镜放大倍数乘以物镜放大倍数得出：总放大倍数 = 目镜放大倍数 × 物镜放大倍数。
ses magnify 10×, so if you use a 40× objective, the total magnification is 10 × 40 = 400×.
典型的目镜放大 10 倍，若使用 40 倍物镜，则总放大倍数为 10 × 40 = 400 倍。
2. Photosynthesis Word Equation | 光合作用文字方程式
Photosynthesis is the process by which green plants and algae make their own food using light energy. The word equation is:
carbon dioxide + water → glucose + oxygen (in the presence of light and chlorophyll).
光合作用是绿色植物和藻类利用光能制造自身养料的过程。其文字方程式为：
二氧化碳 + 水 → 葡萄糖 + 氧气（需要光和叶绿素）。
In symbols, the overall reaction is often written as: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂.
用化学式表示的总反应常写作：6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂。
Glucose can be used immediately for respiration, stored as insoluble starch or converted into other molecules such as cellulose for cell walls.
生成的葡萄糖可立刻用于呼吸作用，以不可溶淀粉的形式储存，或转化为其他分子，如构成细胞壁的纤维素。
3. Aerobic Respiration Word Equation | 有氧呼吸文字方程式
Aerobic respiration releases energy from glucose using oxygen. The word equation is:
glucose + oxygen → carbon dioxide + water (+ energy released).
有氧呼吸利用氧气从葡萄糖中释放能量。文字方程式为：
葡萄糖 + 氧气 → 二氧化碳 + 水（+ 释放的能量）。
Chemically: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O (plus energy). This reaction takes place continuously in the mitochondria of living cells.
化学反应为：C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O（并释放能量）。该反应在活细胞线粒体中持续进行。
4. Anaerobic Respiration in Animals | 动物的无氧呼吸
When oxygen is limited, animal cells can release a small amount of energy through anaerobic respiration. The word equation is:
glucose → lactic acid (+ energy).
在氧气不足时，动物细胞可通过无氧呼吸释放少量能量。文字方程式为：
葡萄糖 → 乳酸（+ 能量）。
Lactic acid build‑up causes muscle fatigue and cramps. After exercise, oxygen is needed to break down the lactic acid – this is called the oxygen debt.
乳酸积聚会导致肌肉疲劳和抽筋。运动后需要氧气来分解乳酸，这称为氧债。
5. Anaerobic Respiration in Plants and Yeast | 植物和酵母的无氧呼吸
In plant cells and yeast, anaerobic respiration produces ethanol and carbon dioxide. The word equation is:
glucose → ethanol + carbon dioxide (+ energy).
在植物细胞和酵母中，无氧呼吸生成乙醇和二氧化碳。文字方程式为：
葡萄糖 → 乙醇 + 二氧化碳（+ 能量）。
Chemically: C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ (+ energy). This type of anaerobic respiration is exploited in baking (CO₂ makes dough rise) and brewing (ethanol is the alcohol in drinks).
化学反应为：C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂（+ 能量）。这种无氧呼吸被用于烘焙（CO₂ 使面团膨胀）和酿造（乙醇是饮料中的酒精）。
6. Enzyme Activity – Temperature and pH | 酶活性与温度和 pH 的关系
Enzymes are biological catalysts that speed up reactions. They have an optimum temperature; for most human enzymes this is around 37 °C. Above the optimum, the active site changes shape and the enzyme denatures permanently.
酶是加速反应的生物催化剂。它们都有一个最适温度；大多数人体酶的最适温度约为 37 °C。超过最适温度后，酶的活性位点形状改变，酶发生永久性变性。
Each enzyme also has an optimum pH. For example, pepsin (in the stomach) works best at pH 2, while amylase (in the mouth and small intestine) prefers pH 7. Extreme pH can denature enzymes in the same way as high temperature.
每种酶也有最适 pH 值。例如，胃蛋白酶在 pH 2 时活性最高，而淀粉酶（口腔和小肠）适宜 pH 7。极端的 pH 值会像高温一样使酶变性。
7. Diffusion, Osmosis and Active Transport | 扩散、渗透与主动运输
Diffusion is the net movement of particles from an area of high concentration to an area of low concentration, down the concentration gradient. It is a passive process (no energy required).
扩散是粒子由高浓度区域向低浓度区域的净移动，即顺浓度梯度。该过程为被动过程，不需要能量。
Osmosis is the diffusion of water molecules across a partially permeable membrane from a dilute solution (high water potential) to a more concentrated solution (low water potential).
渗透是指水分子通过半透膜从稀溶液（高水势）向较浓溶液（低水势）扩散的过程。
Active transport moves substances against the concentration gradient, from low to high concentration, using energy from respiration. Carrier proteins in the cell membrane are essential for this process.
主动运输逆浓度梯度移动物质，即从低浓度侧向高浓度侧，并消耗呼吸作用提供的能量。此过程需要细胞膜上的载体蛋白参与。
8. Factors Affecting the Rate of Photosynthesis | 影响光合作用速率的因素
Light intensity, carbon dioxide concentration and temperature all affect the rate of photosynthesis. If one of these is in short supply, it becomes the limiting factor that holds back the rate.
光照强度、二氧化碳浓度和温度都影响光合作用速率。若其中某一项供应不足，它就会成为限制因素，抑制反应速率。
At low light intensity, the rate of photosynthesis is directly proportional to light intensity. As light intensity continues to increase, the rate eventually levels off when another factor (e.g. CO₂) becomes limiting.
在低光照强度下，光合作用速率与光照强度成正比。随着光照强度继续增加，速率最终趋于平稳，此时另一个因素（如 CO₂）成为限制因素。
Increasing the supply of the limiting factor lifts the rate until a new limiting factor takes over. This concept is frequently tested using graphs with a plateau.
增加限制因素的供应可提升速率，直到出现新的限制因素。考试常通过带有平台的曲线来考查这一概念。
9. Energy Transfer and Pyramids | 能量传递与金字塔
ction: producer → primary consumer → secondary consumer → tertiary consumer. Only about 10% of the energy stored in one trophic level is transferred to the next.
能量沿食物链方向流动：生产者 → 初级消费者 → 次级消费者 → 三级消费者。每个营养级储存的能量只有约 10% 被传递到下一级。
The rest of the energy is lost as heat from respiration, used in movement, or remains undigested and is egested. Pyramids of biomass or pyramids of number show the decreasing amount of living material at higher trophic levels.
其余能量以呼吸热散失，用于运动，或未被消化而排出。生物量金字塔或数量金字塔显示出较高营养级的生物量或个体数量递减。
10. Calculating Percentage Change in Mass | 计算质量变化百分比
When investigating osmosis (e.g. placing potato cylinders in sugar solutions), the change in mass is expressed as a percentage to allow fair comparison. Use the formula:
percentage change = (final mass – initial mass) ÷ initial mass × 100%.
在研究渗透作用时（例如把土豆条放入不同浓度的蔗糖溶液中），质量的变化用百分比表示以便公平比较。所用公式：
变化百分比 = (最终质量 – 初始质量) ÷ 初始质量 × 100%。
A positive percentage indicates water has entered the tissue (increase in mass); a negative percentage shows water has left the tissue. Always plot the processed percentage change on the y‑axis of a graph.
正百分比表示水分进入组织（质量增加）；负百分比表示水分从组织流失。绘图时始终将处理后的百分比变化放在 y 轴上。
11. Surface Area to Volume Ratio | 表面积与体积之比
As an organism or a cell increases in size, its surface area to volume ratio decreases. A large SA:V ratio allows efficient diffusion of gases, nutrients and waste products.
当生物体或细胞体积增大时，其表面积与体积之比减小。较大的 SA:V 比有利于气体、养料和废物的高效扩散。
Small organisms (e.g. amoeba) rely on their large SA:V to exchange materials directly with the environment. Larger organisms need specialised exchange surfaces (e.g. lungs, gills, leaf mesophyll) and transport systems.
小型生物（如变形虫）依靠较大的 SA:V 比直接与环境交换物质。大型生物则需要特化的交换面（如肺、鳃、叶肉组织）和运输系统。
12. Key Unit Conversions for Biology | 生物学重点单位换算
Being confident with unit conversions is essential for microscopy and osmosis calculations. The following equivalents must be memorised:
熟练进行单位换算对显微镜和渗透作用计算至关重要。请务必记住下列换算关系：
| Unit | Equivalent | 说明 |
|---|---|---|
| 1 metre (m) | 100 centimetres (cm) | 1 米 = 100 厘米 |
| 1 centimetre (cm) | 10 millimetres (mm) | 1 厘米 = 10 毫米 |
| 1 millimetre (mm) | 1000 micrometres (µm) | 1 毫米 = 1000 微米 |
| 1 micrometre (µm) | 1000 nanometres (nm) | 1 微米 = 1000 纳米 |
to go to a larger unit, and multiply to go to a smaller unit. For example, to convert 5000 µm to mm, divide by 1000: 5000 ÷ 1000 = 5 mm.
换算时，转换为大单位要除以换算系数，转换为小单位则乘以换算系数。例如，将 5000 µm 转换为 mm，除以 1000：5000 ÷ 1000 = 5 mm。
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