📚 Year 9 CCEA Biology: Formula & Theorem Quick Reference Handbook | 九年级CCEA生物：公式定理速查手册
This handbook compiles the essential formulas, balanced equations and key biological principles required for Year 9 CCEA Biology. It is written as a quick-reference companion for lesson revision, homework support and last-minute preparation before class tests and end-of-unit exams. Every entry states the equation, explains what each term means, and adds the exam-style point that CCEA mark schemes expect to see.
本手册汇编了九年级CCEA生物所需的基本公式、平衡方程式和关键生物学原理，可作为课堂复习、作业辅助以及单元测验与期末考试前突击准备的速查手册。每一条目均给出公式本身、说明各项含义，并补充CCEA评分标准期望看到的考点表述。
1. Photosynthesis Equation | 光合作用方程式
Photosynthesis is the process by which green plants, algae and some bacteria use light energy to convert carbon dioxide and water into glucose and oxygen. The process takes place in the chloroplasts of plant cells and requires the green pigment chlorophyll, which absorbs light energy and transfers it to the reactions of photosynthesis.
光合作用是绿色植物、藻类及某些细菌利用光能将二氧化碳和水转化为葡萄糖和氧气的过程。该过程发生在植物细胞的叶绿体中，并需要绿色色素叶绿素——叶绿素吸收光能并将其传递给光合作用的各个反应。
The word equation summarises the reactants and products:
文字方程式概括了反应物与产物：
Carbon dioxide + Water → Glucose + Oxygen
二氧化碳 + 水 → 葡萄糖 + 氧气
The balanced chemical equation shows that six molecules of carbon dioxide and six molecules of water yield one molecule of glucose and six molecules of oxygen. The equation is balanced because the number of each type of atom is the same on both sides: 6 carbon, 12 hydrogen and 18 oxygen atoms.
平衡化学方程式表明，六分子二氧化碳与六分子水生成一分子葡萄糖和六分子氧气。方程之所以平衡，是因为两边每种原子的数目相同：6个碳原子、12个氢原子和18个氧原子。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Energy is not written as a reactant in the balanced equation, but light energy is essential and is converted into chemical energy stored in the bonds of glucose. The three limiting factors that control the rate of photosynthesis are light intensity, carbon dioxide concentration and temperature.
能量并不作为反应物写入平衡方程式，但光能是必需的，并被转化为储存在葡萄糖化学键中的化学能。控制光合作用速率的三个限制因素是光照强度、二氧化碳浓度和温度。
Rate of photosynthesis ∝ light intensity × CO₂ concentration (at optimum temperature)
光合作用速率 ∝ 光照强度 × 二氧化碳浓度（在最适温度下）
2. Aerobic Respiration Equation | 有氧呼吸方程式
Aerobic respiration occurs in the mitochondria of cells and releases energy from glucose using oxygen. Carbon dioxide and water are produced as waste products, and the energy released is used to make ATP, the universal energy currency of the cell.
有氧呼吸发生在细胞的线粒体中，利用氧气从葡萄糖中释放能量。二氧化碳和水作为废物产生，释放出的能量用于合成ATP——细胞的通用能量货币。
The word equation for aerobic respiration is:
有氧呼吸的文字方程式为：
Glucose + Oxygen → Carbon dioxide + Water + Energy (ATP)
葡萄糖 + 氧气 → 二氧化碳 + 水 + 能量 (ATP)
The balanced chemical equation mirrors photosynthesis in reverse, releasing the energy stored in glucose. Comparing the two equations is a common CCEA question: photosynthesis is endothermic and stores energy, while respiration is exothermic and releases it.
平衡化学方程式与光合作用互为逆反应，释放储存在葡萄糖中的能量。比较这两个方程式是CCEA常见考题：光合作用是吸能反应、储存能量，而呼吸作用是放能反应、释放能量。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 能量
A useful way to remember the link is that the products of photosynthesis are the reactants of respiration, and the products of respiration are the reactants of photosynthesis in plants during daylight hours.
记住二者联系的一个实用方法是：光合作用的产物正是呼吸作用的反应物，而呼吸作用的产物在白天又是植物光合作用的反应物。
3. Anaerobic Respiration and Fermentation | 无氧呼吸与发酵
When oxygen is unavailable, cells carry out anaerobic respiration. Far less energy is released per glucose molecule than in aerobic respiration because glucose is only partially broken down, so oxidised products such as carbon dioxide and water are not formed in the same way.
当氧气不足时，细胞进行无氧呼吸。每分子葡萄糖释放的能量远少于有氧呼吸，因为葡萄糖只被部分分解，因此不会像有氧呼吸那样生成完全氧化的产物二氧化碳和水。
In animal cells, including human muscle cells, glucose is converted into lactic acid. Lactic acid builds up in muscles during vigorous exercise and causes fatigue and cramp; it is later broken down when oxygen becomes available, a state known as oxygen debt.
在动物细胞（包括人体肌肉细胞）中，葡萄糖转化为乳酸。剧烈运动时乳酸在肌肉中堆积，引起疲劳和抽筋；当氧气重新供应时，乳酸会被分解，这种状态称为氧债。
Glucose → Lactic acid + Energy (animal muscle cells)
葡萄糖 → 乳酸 + 能量（动物肌肉细胞）
In plant cells and yeast, anaerobic respiration is called fermentation. Glucose is converted into ethanol and carbon dioxide. Yeast fermentation is exploited in brewing and bread-making, where the carbon dioxide produced makes dough rise.
在植物细胞和酵母中，无氧呼吸被称为发酵。葡萄糖转化为乙醇和二氧化碳。酵母发酵被应用于酿造和面包制作，产生的二氧化碳使面团膨胀。
Glucose → Ethanol + Carbon dioxide + Energy (yeast and plant cells)
葡萄糖 → 乙醇 + 二氧化碳 + 能量（酵母与植物细胞）
- Anaerobic respiration in muscle releases about 1/19 of the energy of aerobic respiration per glucose molecule. | 肌肉中的无氧呼吸每分子葡萄糖释放的能量约为有氧呼吸的1/19。
- gen debt (dm³) = oxygen required to remove lactic acid − oxygen available during exercise. | 氧债（dm³）＝ 清除乳酸所需氧气 − 运动期间可获得的氧气。
4. Enzymes and the Lock-and-Key Model | 酶与锁钥模型
Enzymes are biological catalysts made of protein. They speed up the rate of chemical reactions in living organisms without being used up themselves. According to the lock-and-key model, the substrate molecule fits exactly into the active site of the enzyme, forming an enzyme-substrate complex.
酶是由蛋白质构成的生物催化剂。它们加快生物体内化学反应速率，而自身不被消耗。根据锁钥模型，底物分子像钥匙一样精确嵌入酶的活性位点，形成酶-底物复合物。
Enzyme + Substrate ⇌ Enzyme-substrate complex → Enzyme + Product
酶 + 底物 ⇌ 酶-底物复合物 → 酶 + 产物
Each enzyme has an optimum temperature and an optimum pH at which its rate of reaction is highest. Above the optimum temperature, the bonds holding the protein together vibrate and break, so the active site changes shape. The enzyme is said to be denatured, and the substrate can no longer fit. Denaturation is permanent and cannot be reversed by cooling.
每种酶都有使反应速率最高的最适温度和最适pH。超过最适温度后，维持蛋白质结构的键因振动而断裂，活性位点形状改变，酶被称为变性，底物无法再嵌入。变性是永久性的，冷却也不能使其恢复。
The rate of an enzyme-controlled reaction is calculated from experimental data in the same way as any rate:
酶促反应的速率和其他任何反应一样，可由实验数据计算得出：
Rate of reaction = Amount of product formed ÷ Time taken
反应速率 = 生成产物的量 ÷ 所用时间
The temperature coefficient Q₁₀ compares reaction rates at temperatures 10 °C apart. A Q₁₀ of about 2 means the rate doubles for every 10 °C rise, until the optimum is reached.
温度系数Q₁₀用于比较温度相差10 °C时的反应速率。Q₁₀约为2表示温度每升高10 °C速率加倍，直到达到最适温度为止。
Q₁₀ = Rate at T + 10 °C ÷ Rate at T °C
Q₁₀ = 温度 (T + 10 °C) 时的速率 ÷ 温度 T 时的速率
5. Microscope Magnification and Scale | 显微镜放大倍数与标尺
The total magnification of a light microscope is found by multiplying the magnification of the eyepiece lens by the magnification of the objective lens. This formula appears in almost every CCEA practical question on cells.
光学显微镜的总放大倍数等于目镜放大倍数与物镜放大倍数的乘积。这一公式几乎出现在每一道CCEA关于细胞的实验题中。
Total magnification = Eyepiece magnification × Objective magnification
总放大倍数 = 目镜放大倍数 × 物镜放大倍数
To estimate the real size of a specimen, rearrange the magnification relationship. Remember to convert units before answering, since CCEA frequently awards a mark for correct unit conversion.
要估算标本的实际大小，可对放大倍数关系式进行变形。切记在作答前换算单位，因为CCEA常为正确的单位换算单独给分。
Actual size = Image size ÷ Magnification
实际大小 = 图像大小 ÷ 放大倍数
Magnification = Image size ÷ Actual size
放大倍数 = 图像大小 ÷ 实际大小
Unit conversions you must know:
必须掌握的单位换算：
- 1 mm = 1000 μm (micrometres) | 1 mm = 1000 μm（微米）
- 1 μm = 1000 nm (nanometres) | 1 μm = 1000 nm（纳米）
- 1 cm = 10 mm = 10 000 μm | 1 cm = 10 mm = 10 000 μm
under a ×400 magnification. The actual width is 20 mm ÷ 400 = 0.05 mm, which equals 50 μm.
示例：某细胞在×400放大倍数下宽20 mm。其实际宽度为 20 mm ÷ 400 = 0.05 mm，即50 μm。
6. Surface Area to Volume Ratio | 表面积与体积比
The surface area to volume ratio explains why cells are small and why exchange surfaces in organisms are highly folded. As an object gets larger, its volume increases faster than its surface area, so the ratio falls.
表面积与体积之比解释了细胞为何体积小，以及生物体的交换表面为何高度折叠。物体越大，体积增长快于表面积增长，因此比值下降。
Surface area to volume ratio = Surface area ÷ Volume
表面积与体积比 = 表面积 ÷ 体积
The formulas for the two shapes most commonly examined are shown below. For a cube of side s, the ratio simplifies to 6 ÷ s; for a sphere of radius r, it simplifies to 3 ÷ r.
下面给出最常考的两种立体图形的公式。边长为s的正方体，比值可简化为 6 ÷ s；半径为r的球体，比值可简化为 3 ÷ r。
Cube: Surface area = 6s², Volume = s³, Ratio = 6 ÷ s
正方体：表面积 = 6s²，体积 = s³，比值 = 6 ÷ s
Sphere: Surface area = 4πr², Volume = 4/3 πr³, Ratio = 3 ÷ r
球体：表面积 = 4πr²，体积 = 4/3 πr³，比值 = 3 ÷ r
A small cell with a high ratio can supply its contents with oxygen and nutrients by diffusion alone. A large organism cannot, which is why it needs specialised exchange surfaces such as alveoli, villi and gill lamellae, and a transport system to move substances around the body.
比值高的小细胞仅靠扩散即可为其内部提供氧气和营养。大型生物则不能，因此需要特化的交换表面（如肺泡、小肠绒毛和鳃小片）以及运输系统在体内运送物质。
7. Diffusion, Osmosis and Water Potential | 扩散、渗透与水势
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient. It is a passive process and requires no energy from the cell.
扩散是粒子从高浓度区域向低浓度区域的净移动，即顺浓度梯度移动。它是被动过程，不需要细胞提供能量。
The rate of diffusion depends on three factors, summarised below. This relationship is sometimes called Fick's law and is the reason exchange surfaces are thin, moist and richly supplied with blood.
扩散速率取决于三个因素，其关系总结如下。这一关系有时称为菲克定律，也正是交换表面薄、湿润且血液供应丰富的原因。
Rate of diffusion ∝ (Surface area × Concentration difference) ÷ Thickness of membrane
扩散速率 ∝ （表面积 × 浓度差）÷ 膜厚度
Osmosis is a special case of diffusion: the movement of water molecules from a region of higher water potential to a region of lower water potential through a partially permeable membrane. Water potential is measured in kilopascals (kPa) and pure water has a water potential of zero.
渗透是扩散的一种特殊情形：水分子通过部分可透性膜，从水势较高的区域向水势较低的区域移动。水势以千帕（kPa）为单位，纯水的水势规定为零。
Water potential (ψ) = Solute potential (ψₛ) + Pressure potential (ψₚ)
水势 (ψ) = 溶质势 (ψₛ) + 压力势 (ψₚ)
- Adding solute lowers water potential, so ψₛ is negative in solutions. | 加入溶质会降低水势，因此溶液中ψₛ为负值。
- Water always moves from a less negative ψ to a more negative ψ. | 水总是从ψ较不负值的一侧流向较负值的一侧。
- In plant cells, the cell wall resists expansion and produces a positive pressure potential. | 在植物细胞中，细胞壁抵抗膨大，产生正的压力势。
8. Transpiration and Transpiration Rate | 蒸腾作用与蒸腾速率
Transpiration is the loss of water vapour from the leaves of a plant, mainly through the stomata. It creates the transpiration stream that pulls water up the xylem from the roots, and it also helps to cool the leaf.
蒸腾作用是水分以水蒸气形式从植物叶片散失的过程，主要通过气孔进行。它形成蒸腾流，将水从根部沿木质部向上拉，同时也有助于叶片降温。
The rate of transpiration can be measured with a potometer and calculated using a simple rate formula based on the distance moved by the air bubble.
蒸腾速率可用蒸腾计测量，并基于气泡移动的距离用简单的速率公式计算。
Transpiration rate = Volume of water lost ÷ Time taken
蒸腾速率 = 散失的水量 ÷ 所用时间
Transpiration rate = Distance moved by air bubble ÷ Time taken
蒸腾速率 = 气泡移动距离 ÷ 所用时间
Four environmental factors control the rate, and CCEA expects you to explain each one in terms of diffusion, evaporation or stomatal behaviour:
有四个环境因素控制蒸腾速率，CCEA要求你从扩散、蒸发或气孔行为的角度逐一解释：
| Factor | 因素 | Effect | 影响 | Reason | 原因 |
| Light intensity | 光照强度 | Increases rate | 提高速率 | Stomata open in light | 光照下气孔张开 |
| Temperature | 温度 | Increases rate | 提高速率 | Faster evaporation and diffusion | 蒸发和扩散加快 |
| Humidity | 湿度 | Decreases rate | 降低速率 | Smaller water vapour concentration gradient | 水蒸气浓度梯度变小 |
| Wind speed | 风速 | Increases rate | 提高速率 | Removes humid air from the leaf surface | 带走叶面湿润空气 |
9. Genetics: Punnett Squares and Probability | 遗传学：Punnett方格与概率
A Punnett square is a grid used to predict the possible genotypes of offspring from a genetic cross. Alleles are written as letters: a capital letter represents the dominant allele and a lower-case letter represents the recessive allele.
Punnett方格是一种用于预测杂交后代可能基因型的表格。等位基因用字母表示：大写字母代表显性等位基因，小写字母代表隐性等位基因。
Key definitions you must use precisely:
必须准确使用的关键定义：
- Genotype: the combination of alleles an organism carries, for example Tt. | 基因型：生物体所携带的等位基因组合，例如Tt。
- Phenotype: the observable characteristic produced, for example tall. | 表现型：表现出的可观察性状，例如高茎。
- Homozygous: two identical alleles, TT or tt. | 纯合：两个相同的等位基因，TT或tt。
- Heterozygous: two different alleles, Tt. | 杂合：两个不同的等位基因，Tt。
dominant to 1 recessive in the offspring, while a test cross (Tt × tt) gives a 1:1 ratio.
两个杂合亲本杂交（Tt × Tt）在后代中产生经典的3:1显隐比，而测交（Tt × tt）产生1:1的比例。
Tt × Tt → 1 TT : 2 Tt : 1 tt (3 dominant : 1 recessive)
Tt × Tt → 1 TT : 2 Tt : 1 tt（3显性 : 1隐性）
Probability is expressed as a fraction, decimal or percentage, and the formula below converts a Punnett square into a numerical answer.
概率可用分数、小数或百分数表示，下面的公式可将Punnett方格转化为数值答案。
Probability = Number of favourable outcomes ÷ Total number of possible outcomes
概率 = 有利结果数 ÷ 可能结果总数
10. DNA Structure and Base Pairing | DNA结构与碱基配对
DNA is a polymer made of repeating units called nucleotides. Each nucleotide contains a phosphate group, a deoxyribose sugar and one of four bases: adenine (A), thymine (T), cytosine (C) and guanine (G).
DNA是由称为核苷酸的重复单元构成的多聚体。每个核苷酸含有一个磷酸基团、一个脱氧核糖以及四种碱基之一：腺嘌呤（A）、胸腺嘧啶（T）、胞嘧啶（C）和鸟嘌呤（G）。
Two DNA strands twist around each other to form a double helix, held together by complementary base pairing. Because A always pairs with T and C always pairs with G, the percentage of A equals the percentage of T, and the percentage of C equals the percentage of G.
两条DNA链相互盘绕形成双螺旋，由互补碱基配对维系。由于A总是与T配对，C总是与G配对，因此A的百分比等于T的百分比，C的百分比等于G的百分比。
A pairs with T (2 hydrogen bonds); C pairs with G (3 hydrogen bonds)
A与T配对（2个氢键）；C与G配对（3个氢键）
%A = %T, %C = %G, so %A + %T + %C + %G = 100%
%A = %T，%C = %G，因此 %A + %T + %C + %G = 100%
For example, if a DNA sample contains 22% adenine, it must also contain 22% thymine. That leaves 56% shared equally between C and G, so cytosine makes up 28% of the bases.
例如，若某DNA样品含22%的腺嘌呤，则必定也含22%的胸腺嘧啶。剩余56%由C和G均分，因此胞嘧啶占碱基总数的28%。
11. Ecology: Energy Transfer and the 10% Rule | 生态学：能量传递与10%定律
Energy flows through a food chain from producers to primary consumers, secondary consumers and tertiary consumers. Only a small proportion of the energy at one trophic level is passed on to the next, because energy is lost through respiration, movement, excretion and as heat.
能量沿食物链从生产者流向初级消费者、次级消费者和三级消费者。由于能量通过呼吸、运动、排泄以及以热能形式散失，某一营养级的能量只有很小一部分传递到下一营养级。
The efficiency of energy transfer is calculated with the formula below. In most food chains the answer is roughly
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