📚 Year 9 Edexcel Biology: Formula & Theorem Quick Reference Guide | 九年级爱德思生物：公式定理速查手册
This quick reference guide collects essential formulas, key principles, and foundational theorems from the Year 9 Edexcel Biology syllabus. Use it to revise microscope calculations, metabolic equations, genetic patterns, and physiological relationships that often appear in exam questions. Each entry is presented as a bilingual explanation – read the English, then check the Chinese – so you can build both understanding and accurate scientific vocabulary.
这本速查手册整理了九年级爱德思生物课程中必不可少的公式、关键原理和基础定理。它涵盖了显微镜计算、新陈代谢方程式、遗传规律以及生理关系等考试常见内容。每个条目都采用中英双语解释——先读英文，再看中文——帮助你既理解概念，又积累准确的科学词汇。
1. Magnification Formula | 放大率公式
Magnification is how much larger an image appears compared to the real object. The formula links image size, actual size, and magnification: Magnification = Image size ÷ Actual size = Image size ÷ Magnification. This is vital when drawing scale bars or estimating cell dimensions from microscope images.
放大率指图像相对于实物放大的倍数。公式为：放大率 = 图像尺寸 ÷ 实际尺寸。务必保证两个尺寸单位相同，常用毫米（mm）或微米（μm）。变形公式为：实际尺寸 = 图像尺寸 ÷ 放大率。在绘制比例尺或根据显微镜图像估算细胞大小时，这个公式非常重要。
2. Actual Size and Unit Conversions | 实际尺寸与单位换算
00 nm. To convert a measurement from mm to μm, multiply by 1000. To go from μm to mm, divide by 1000. When calculating actual size, always convert your image size measurement into the unit matching the scale bar or given data before applying the formula.
生物学家常用毫米（mm）、微米（μm）和纳米（nm）。1 mm = 1000 μm；1 μm = 1000 nm。从毫米换算为微米要乘以1000，从微米换算为毫米要除以1000。在计算实际尺寸时，务必先将图像尺寸的单位转换为与比例尺或给定数据一致，再代入公式。
3. Surface Area to Volume Ratio | 表面积与体积比
ces to move in and out quickly. For a cube, surface area = 6 × side², volume = side³. Single-celled organisms rely on this ratio for efficient exchange; larger multicellular organisms need specialised exchange surfaces like alveoli and villi to increase surface area.
随着生物体或细胞变大，其表面积与体积之比会减小。该比值影响扩散速率：高 SA:V 能让物质快速进出。对于立方体，表面积 = 6 × 边长²，体积 = 边长³。单细胞生物依靠高比值进行高效交换；大型多细胞生物则需要肺泡、小肠绒毛等特化交换表面来增加表面积。
4. Photosynthesis Word Equation | 光合作用文字方程
Photosynthesis is the process by which plants and algae produce glucose and oxygen using light energy. The word equation summarises the reactants and products:
Carbon dioxide + Water → Glucose + Oxygen
Light energy is absorbed by chlorophyll in chloroplasts. This reaction is essential for converting light energy into chemical energy stored in carbohydrates. Remember that photosynthesis requires light and chlorophyll; it does not happen in animal cells.
光合作用是植物和藻类利用光能生成葡萄糖和氧气的过程。文字方程式概括了反应物和产物：
二氧化碳 + 水 → 葡萄糖 + 氧气
光能被叶绿体中的叶绿素吸收。该反应将光能转化为储存在碳水化合物中的化学能。请记住，光合作用需要光和叶绿素，动物细胞无法进行。
5. Aerobic Respiration Equation | 有氧呼吸方程
Aerobic respiration occurs in the mitochondria when oxygen is present. Glucose is fully broken down to release a large amount of energy. The word equation is:
Glucose + Oxygen → Carbon dioxide + Water (+ energy)
The energy released is used to form ATP, which powers cellular activities such as muscle contraction, active transport, and building new molecules. Carbon dioxide and water are waste products that are removed from the body.
有氧呼吸在线粒体中进行，需要氧气参与。葡萄糖被完全分解，释放大量能量。文字方程为：
葡萄糖 + 氧气 → 二氧化碳 + 水（+ 能量）
释放的能量用于合成 ATP，驱动肌肉收缩、主动运输和合成新分子等细胞活动。二氧化碳和水是废物，会被排出体外。
6. Anaerobic Respiration in Animals and Yeast | 动物与酵母的无氧呼吸
When oxygen is limited, cells switch to anaerobic respiration. In animal muscle cells, glucose is broken down into lactic acid, releasing a small amount of energy:
Glucose → Lactic acid (+ energy)
Lactic acid build-up causes muscle fatigue. In yeast and some plants, the process is fermentation, producing ethanol and carbon dioxide:
Glucose → Ethanol + Carbon dioxide (+ energy)
Anaerobic respiration yields much less ATP than aerobic respiration.
缺氧时，细胞会转为无氧呼吸。在动物肌肉细胞中，葡萄糖分解为乳酸，释放少量能量：
葡萄糖 → 乳酸（+ 能量）
乳酸积累会导致肌肉疲劳。在酵母和某些植物中，这是发酵过程，产生乙醇和二氧化碳：
葡萄糖 → 乙醇 + 二氧化碳（+ 能量）
无氧呼吸产生的 ATP 远少于有氧呼吸。
7. Enzyme–Substrate Theory | 酶–底物理论
Enzymes are biological catalysts that speed up reactions without being used up. The active site of an enzyme has a specific shape complementary to its substrate. This is often described by the lock and key model: the substrate fits into the active site like a key into a lock, forming an enzyme–substrate complex. After the reaction, products are released and the enzyme is unchanged. Temperature and pH affect the shape of the active site; beyond the optimum, the enzyme may denature.
酶是生物催化剂，能加快反应而自身不被消耗。酶的活性位点具有与底物互补的特定形状，常被描述为锁钥模型：底物像钥匙一样嵌入活性位点，形成酶–底物复合物。反应后产物释放，酶不变。温度和 pH 会影响活性位点形状；超出最适条件，酶可能变性。
8. Food Tests – Key Reagents and Colour Changes | 食物测试 – 关键试剂与颜色变化
Four standard food tests help identify nutrients:
- Starch: Add iodine solution; a blue-black colour indicates starch.
- Reducing sugars (e.g., glucose): Mix with Benedict's solution and heat in a water bath; a brick-red precipitate forms.
- Protein: Add Biuret reagent (sodium hydroxide then copper sulfate); a violet/purple colour appears.
- Lipids (fats): Rub a food sample on filter paper; a translucent spot suggests the presence of lipid. Alternatively, the ethanol emulsion test: shake with ethanol, then add water – a cloudy white emulsion forms.
四种标准食物测试帮助鉴定营养物质：
- 淀粉：加入碘液，蓝黑色表示含有淀粉。
- 还原糖（如葡萄糖）：与本尼迪克特试剂混合后水浴加热，生成砖红色沉淀。
- 蛋白质：加入双缩脲试剂（先氢氧化钠，后硫酸铜），出现紫色或紫罗兰色。
- 脂类（脂肪）：将食物样品在滤纸上摩擦，透明点表示含有脂质。或者用乙醇乳化法：加乙醇振荡，再加水，形成乳白色浑浊。
9. Energy Requirements and BMI | 能量需求与体质指数
Daily energy needs depend on age, sex, activity level, and physiological state such as pregnancy. The energy released by food is measured in kilojoules (kJ) or kilocalories (kcal). A rough guide is that 1 g of carbohydrate or protein provides about 17 kJ, while 1 g of fat provides about 38 kJ. Body Mass Index (BMI) is calculated by:
BMI = mass (kg) ÷ height² (m²)
BMI helps assess whether a person is underweight, healthy, overweight, or obese, but it does not account for muscle mass directly.
每日能量需求取决于年龄、性别、活动水平以及怀孕等生理状态。食物释放的能量以千焦（kJ）或千卡（kcal）计量。大致估算：1克碳水化合物或蛋白质约提供17 kJ，1克脂肪约提供38 kJ。体质指数（BMI）的计算公式为：
BMI = 体重（kg）÷ 身高²（m²）
BMI 用于判断体重过轻、正常、超重或肥胖，但它不能直接反映肌肉量。
10. Monohybrid Inheritance – Dominant and Recessive Alleles | 单基因遗传 – 显性与隐性等位基因
Genes come in different forms called alleles. A dominant allele (represented by a capital letter, e.g., T for tall) expresses its trait even if only one copy is present. A recessive allele (lowercase, e.g., t for short) only shows when two copies are present. A Punnett square is used to predict offspring genotypes and phenotypes. If a heterozygous tall plant (Tt) is crossed with a short plant (tt), the expected ratio is 1 tall : 1 short.
基因有不同的存在形式，称为等位基因。显性等位基因（用大写字母表示，如 T 代表高茎）只要有一个拷贝就能表现性状。隐性等位基因（用小写字母，如 t 代表矮茎）只有在有两个拷贝时才会表现。庞尼特方格用于预测后代的基因型和表现型。如果杂合高茎植株（Tt）与矮茎植株（tt）杂交，预期比例为 1 高茎 : 1 矮茎。
11. Sex Determination and Chromosomes | 性别决定与染色体
In humans, sex is determined by the 23rd pair of chromosomes. Females have two X chromosomes (XX); males have one X and one Y chromosome (XY). The sex of a child depends on whether the sperm carries an X or a Y chromosome. A Punnett square shows a 50% chance of female (XX) and 50% chance of male (XY) offspring. It is the father’s gamete that ultimately determines the sex.
人类的性别由第23对染色体决定。女性有两条 X 染色体（XX），男性有一条 X 和一条 Y 染色体（XY）。孩子的性别取决于精子携带的是 X 还是 Y 染色体。庞尼特方格显示，女性（XX）和男性（XY）后代的理论概率各为 50%。最终决定性别的是父亲的配子。
12. Factors Affecting Diffusion Rate | 影响扩散速率的因素
Diffusion is the net movement of particles from a region of high concentration to low concentration. The rate depends on:
- Concentration gradient: steeper gradient → faster diffusion.
- Temperature: higher temperature → particles have more kinetic energy → faster diffusion.
- Surface area: larger area allows more particles to cross per unit time.
- Diffusion distance: shorter distance → faster exchange.
These factors are captured in Fick’s law, but at Year 9 level, you only need to reason qualitatively.
扩散是粒子从高浓度区域向低浓度区域的净移动。速率取决于：
- 浓度梯度：梯度越大 → 扩散越快。
- 温度：温度越高 → 粒子动能越大 → 扩散越快。
- 表面积：面积越大，单位时间内通过的粒子越多。
- 扩散距离：距离越短 → 交换越快。
这些因素体现在菲克定律中，但在九年级阶段只需进行定性分析。
Published by TutorHao | Biology Revision Series | aleveler.com
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