📚 Year 8 OCR Biology: Quick-Reference Handbook of Formulas and Principles | 八年级OCR生物：公式定理速查手册
This handbook brings together the most important formulas, equations, and key scientific principles you will meet in Year 8 OCR Biology. Use it as a rapid recap to support your revision, homework, and preparation for end-of-topic tests. From microscope magnification to the lock-and-key model, each section gives you the core rule followed by a clear explanation in both English and Chinese so you can strengthen your understanding and your scientific vocabulary.
本手册汇集了八年级OCR生物课程中最重要的公式、方程式和关键科学原理。它可以作为快速回顾的资料，帮助你复习、做作业和准备单元测试。从显微镜放大倍数到锁钥模型，每个部分都先给出核心规则，再用中英双语清晰解释，帮助你同时加深理解和扩充科学词汇。
1. The Microscope Magnification Formula | 显微镜放大倍数公式
The total magnification of a light microscope is calculated by multiplying the magnification of the eyepiece lens by the magnification of the objective lens. The formula is: Magnification = eyepiece lens magnification × objective lens magnification.
光学显微镜的总放大倍数是目镜放大倍数与物镜放大倍数相乘得到的。公式为：放大倍数 = 目镜放大倍数 × 物镜放大倍数。
For example, if the eyepiece lens is ×10 and the objective lens is ×40, the total magnification is 10 × 40 = ×400.
例如，若目镜为×10，物镜为×40，则总放大倍数为10 × 40 = ×400。
When you draw a biological specimen, you can calculate the drawing magnification by dividing the size of the drawing by the real size of the specimen. Both must be in the same units. The formula is: Drawing magnification = drawing size ÷ actual size.
当你绘制生物标本图时，可以用图画尺寸除以标本实际尺寸来计算绘图放大倍数，两者须使用相同单位。公式为：绘图放大倍数 = 图画尺寸 ÷ 实际尺寸。
2. Key Principles of Animal and Plant Cells | 动植物细胞的关键原理
All living organisms are made of cells. Animal cells contain several key organelles: nucleus, cytoplasm, cell membrane, mitochondria and ribosomes. Plant cells share these parts but also have three extra structures: cell wall, chloroplasts and a large permanent vacuole.
所有生物都由细胞构成。动物细胞含有若干关键细胞器：细胞核、细胞质、细胞膜、线粒体和核糖体。植物细胞除了这些部分外，还多出三种结构：细胞壁、叶绿体和一个大型中央液泡。
Nucleus: controls all cell activities and stores genetic material (DNA).
细胞核：控制细胞的一切活动并储存遗传物质（DNA）。
Cytoplasm: jelly-like substance where most chemical reactions take place.
细胞质：果冻状物质，大多数化学反应在此发生。
Cell membrane: a selectively permeable barrier that controls what enters and leaves the cell.
细胞膜：选择性通透的屏障，控制物质进出细胞。
Mitochondria: the site of aerobic respiration, releasing energy from glucose.
线粒体：有氧呼吸的场所，从葡萄糖中释放能量。
Ribosomes: tiny structures where proteins are made (protein synthesis).
核糖体：微小的结构，蛋白质在此合成（蛋白质合成）。
Cell wall (plants only): a rigid outer layer made of cellulose that provides support and shape.
细胞壁（仅植物）：由纤维素构成的坚硬外层，提供支撑和固定形状。
Chloroplasts (plants only): contain chlorophyll, which absorbs light energy for photosynthesis.
叶绿体（仅植物）：含有叶绿素，吸收光能以进行光合作用。
Large permanent vacuole (plants only): a fluid-filled sac that stores cell sap and helps keep the cell firm.
大型中央液泡（仅植物）：充满液体的囊泡，储存细胞液并帮助细胞保持硬挺。
3. Diffusion and Osmosis Principles | 扩散与渗透原理
Diffusion is the net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient, until they are evenly spread. It is a passive process that does not require 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，沿浓度梯度进行，直至均匀分布。这是一个被动过程，不需要细胞提供能量。
Osmosis is a special case of diffusion. It is the movement of water molecules from a dilute solution (high water potential) to a more concentrated solution (low water potential) through a partially permeable membrane.
渗透是扩散的一种特殊情况。它是指水分子通过部分透性膜从稀溶液（高水势）向较浓溶液（低水势）的移动。
A partially permeable membrane allows small molecules like water to pass through but does not allow larger solute molecules to cross freely.
部分透性膜允许水等小分子通过，但不允许较大的溶质分子自由穿过。
4. Photosynthesis Equation | 光合作用方程式
Photosynthesis is the process by which plants and some other organisms use light energy to convert carbon dioxide and water into glucose and oxygen. The process takes place in chloroplasts and requires chlorophyll. The overall word equation is: carbon dioxide + water → glucose + oxygen.
光合作用是植物及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。该过程在叶绿体中进行，需要叶绿素。总文字方程式为：二氧化碳 + 水 → 葡萄糖 + 氧气。
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Light energy is trapped by the green pigment chlorophyll. Oxygen is released as a by-product, and the glucose produced can be used for respiration, stored as starch, or turned into cellulose for cell walls.
光能被绿色色素叶绿素捕获。氧气作为副产品释放，产生的葡萄糖可用于呼吸作用、以淀粉形式储存或转变为构成细胞壁的纤维素。
5. Aerobic Respiration Equation | 有氧呼吸方程式
Aerobic respiration takes place in the mitochondria of cells when oxygen is available. It releases a large amount of energy from the breakdown of glucose. The overall word equation is: glucose + oxygen → carbon dioxide + water (+ energy released).
有氧呼吸在细胞线粒体中进行，需要有氧气存在。它通过分解葡萄糖释放大量能量。总文字方程式为：葡萄糖 + 氧气 → 二氧化碳 + 水（+ 释放的能量）。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O
The energy released is used to power many life processes, such as muscle contraction, active transport, and keeping body temperature constant in mammals.
释放的能量用于驱动许多生命活动，如肌肉收缩、主动运输以及哺乳动物的体温恒定。
6. Anaerobic Respiration Equations | 无氧呼吸方程式
Anaerobic respiration occurs when there is not enough oxygen to meet the energy demand. It releases less energy than aerobic respiration and does not take place in mitochondria alone. In humans, glucose is broken down into lactic acid: glucose → lactic acid (+ some energy).
当氧气不足以满足能量需求时，就会发生无氧呼吸。它释放的能量比有氧呼吸少，并且不完全在线粒体中进行。在人体中，葡萄糖被分解为乳酸：葡萄糖 → 乳酸（+ 少量能量）。
Lactic acid build-up in muscles can cause cramp and fatigue. After exercise, oxygen is needed to break down the lactic acid — this is known as repaying the oxygen debt.
肌肉中乳酸堆积会引起抽筋和疲劳。运动后需要氧气来分解乳酸，这称为偿还氧债。
In yeast and some plants, anaerobic respiration produces ethanol and carbon dioxide: glucose → ethanol + carbon dioxide (+ some energy). This process is called fermentation and is used to make bread and alcoholic drinks.
在酵母和某些植物中，无氧呼吸产生乙醇和二氧化碳：葡萄糖 → 乙醇 + 二氧化碳（+ 少量能量）。这一过程称为发酵，用于制作面包和酒精饮料。
7. Food Chains and Energy Flow | 食物链与能量流动
A food chain shows the feeding relationships between organisms in an ecosystem. It always begins with a producer, normally a green plant, that captures light energy and converts it into chemical energy through photosynthesis. The arrow (→) points in the direction of energy transfer and food flow: from the organism being eaten to the organism that eats it.
食物链显示生态系统中生物之间的取食关系。它总是从生产者开始，通常是绿色植物，通过光合作用捕获光能并将其转化为化学能。箭头（→）指向能量传递和食物流动的方向：从被吃的生物指向吃它的生物。
Energy decreases at each trophic level because most of it is lost through movement, heat, waste materials and uneaten parts. Typically, only about 10% of the energy is passed on to the next level. This limits the length of food chains.
能量在每个营养级都会减少，因为大部分能量通过运动、热量、排泄物和未食用的部分而耗散。通常只有约10%的能量传递到下一营养级，这限制了食物链的长度。
8. Predator-Prey Population Cycles | 捕食者-猎物数量循环原理
In a predator-prey relationship, the population sizes of predator and prey follow a cyclical pattern. If the prey population increases, there is more food for the predators, so the predator population also increases. As predators increase, they eat more prey, causing the prey population to decrease. With fewer prey available, the predator population then decreases, allowing the prey numbers to rise again.
在捕食者-猎物关系中，捕食者和猎物的种群数量呈周期性变化。如果猎物数量增加，捕食者有更多食物，因此捕食者数量随之上升。随着捕食者增多，它们吃掉更多猎物，导致猎物数量减少。当猎物变少，捕食者数量又下降，从而使猎物数量再次上升。
This pattern can be seen in the classic example of the Canadian lynx and the snowshoe hare. The peaks and troughs of the two populations follow each other closely but with a slight lag.
这种模式可见于加拿大猞猁与雪靴兔的经典案例。两个种群的波峰和波谷紧密相随，但存在轻微的时间滞后。
9. Enzyme Action: Lock-and-Key Model | 酶作用：锁钥模型
Enzymes are biological catalysts made of protein that speed up chemical reactions in living organisms without being used up. The lock-and-key model explains how enzymes work. Each enzyme has an active site with a specific shape that is complementary to the shape of its substrate.
酶是由蛋白质构成的生物催化剂，可以加速生物体内的化学反应，而自身不被消耗。锁钥模型解释了酶的工作原理。每种酶都有一个活性位点，其特定形状与底物的形状互补。
When the substrate fits into the active site, an enzyme-substrate complex is formed. The reaction then takes place and the products are released, leaving the enzyme unchanged and ready to bind another substrate molecule.
当底物嵌入活性位点，便形成酶-底物复合物。随后反应发生，产物释放，酶本身不变，可继续与另一个底物分子结合。
Enzymes are sensitive to temperature and pH. High temperatures can denature the enzyme by changing the shape of its active site, so the substrate can no longer fit.
酶对温度和pH敏感。高温会使酶的活性位点形状改变，导致变性，底物便无法再匹配。
10. Surface Area to Volume Ratio and Diffusion | 表面积体积比与扩散
The surface area to volume ratio (SA:V) is a key factor that affects the rate of diffusion into and out of cells and organisms. It is calculated by dividing the total surface area by the volume: SA:V ratio = surface area ÷ volume.
表面积与体积之比（SA:V）是影响物质进出细胞和生物体扩散速率的关键因素。它的计算方法是总表面积除以体积：SA:V比值 = 表面积 ÷ 体积。
Small objects have a large surface area relative to their volume, giving them a high SA:V ratio. This allows for rapid diffusion and is why many single-celled organisms can rely on diffusion alone to meet their needs. As organisms get larger, the SA:V ratio decreases, so they need specialized exchange surfaces and transport systems, such as lungs and blood circulation.
小型物体的表面积相对于体积较大，因此SA:V比值高。这使扩散迅速进行，也是许多单细胞生物可以仅靠扩散满足需求的原因。随着生物体增大，SA:V比值下降，因此它们需要特化的交换表面和运输系统，如肺和血液循环。
Example: a cube with side length 1 cm has a surface area of 6 cm² and a volume of 1 cm³, giving a SA:V ratio of 6. A cube of side length 2 cm has a surface area of 24 cm² and a volume of 8 cm³, giving a ratio of 3.
例如：边长为1 cm的立方体表面积为6 cm²，体积为1 cm³，SA:V比值为6。边长为2 cm的立方体表面积为24 cm²，体积为8 cm³，比值为3。
11. Essential Nutrients and Their Functions | 必需营养素及其功能
A balanced diet provides all the essential nutrients in the right amounts. The main nutrient groups and their primary roles must be known for the OCR syllabus.
均衡饮食提供足量的各种必需营养素。OCR教学大纲要求掌握主要营养素组及其基本功能。
Carbohydrates: the body’s main source of energy. Found in bread, pasta and rice. Starch is a large carbohydrate made of many glucose units.
碳水化合物：身体的主要能量来源。富含于面包、面食和米饭中。淀粉是由许多葡萄糖单元构成的大分子碳水化合物。
Proteins: needed for growth and repair of tissues. Made of amino acids. Sources include meat, fish, eggs and beans.
蛋白质：用于组织生长和修复。由氨基酸组成。来源包括肉类、鱼类、蛋类和豆类。
Lipids (fats and oils): provide a concentrated energy store, insulation and protection of organs. Found in butter, oils and nuts.
脂类（脂肪和油）：提供浓缩的能量储备、保温和保护器官。富含于黄油、食用油和坚果中。
Vitamins and minerals: required in small amounts for various functions. For example, vitamin C maintains healthy skin and gums, vitamin D helps calcium absorption for strong bones, and iron is needed to make haemoglobin in red blood cells.
维生素和矿物质：需要量少，但功能多样。例如，维生素C维持皮肤和牙龈健康，维生素D促进钙吸收以强壮骨骼，铁是制造红细胞中血红蛋白所必需的。
Dietary fibre: not digested but helps the movement of food through the digestive system, preventing constipation.
膳食纤维：不被消化，但有助于食物在消化系统内移动，预防便秘。
Water: acts as a solvent for chemical reactions, transports substances and helps regulate body temperature.
水：作为化学反应的溶剂，运输物质，并有助于调节体温。
12. Comparing Photosynthesis and Respiration | 比较光合作用与呼吸作用
Photosynthesis and aerobic respiration are often considered opposite processes, though they play complementary roles in the carbon cycle. Photosynthesis takes in carbon dioxide and water, uses light energy, and produces glucose and oxygen. Aerobic respiration takes in glucose and oxygen and releases carbon dioxide, water and energy.
光合作用与有氧呼吸常被视为相反的过程，但它们在碳循环中互为补充。光合作用吸收二氧化碳和水，利用光能，产生葡萄糖和氧气。有氧呼吸则利用葡萄糖和氧气，释放二氧化碳、水和能量。
Photosynthesis only happens in cells containing chlorophyll when light is present. Respiration happens in all living cells at all times, even though the rate may be lower when organisms are at rest.
光合作用只在含叶绿素的细胞中，在有光的条件下进行。呼吸作用则在所有活细胞中持续进行，即使生物休息时速率较低也在发生。
During the day, plants carry out both photosynthesis and respiration. Often the rate of photosynthesis is higher, so there is a net release of oxygen. At night, photosynthesis stops, but respiration continues, leading to a net uptake of oxygen and release of carbon dioxide.
在白天，植物同时进行光合作用和呼吸作用。通常光合作用速率更高，因此净释放氧气。到了夜晚，光合作用停止，呼吸作用仍在进行，导致净吸收氧气并释放二氧化碳。
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