📚 GCSE Biology: Respiration Revision | GCSE 生物：呼吸作用 考点精讲
Respiration is a fundamental life process that releases energy from food in all living cells. It is not the same as breathing – it is a chemical reaction that happens inside cells. This guide covers everything you need to know for GCSE Biology: aerobic and anaerobic respiration, key equations, energy uses, oxygen debt, and practical investigations.
呼吸作用是所有活细胞从食物中释放能量的基本生命过程。它不同于呼吸（换气）—— 它是发生在细胞内部的化学反应。本指南涵盖 GCSE 生物学你需要掌握的全部内容：有氧呼吸与无氧呼吸、关键方程式、能量用途、氧债以及实验探究。
1. What is Respiration? | 什么是呼吸作用？
Respiration is an exothermic chemical reaction that occurs continuously in the cells of all living organisms. It transfers energy from glucose so that the organism can perform vital functions. This process is enzyme-controlled and takes place in all cells, not just those of muscles or active tissues.
呼吸作用是一种放热的化学反应，持续发生在所有生物体的细胞中。它从葡萄糖中转移能量，使生物体能够行使重要的生命功能。该过程受酶控制，在所有细胞中发生，而不仅仅发生在肌肉或活跃组织中。
The energy released during respiration is temporarily stored in molecules of ATP (adenosine triphosphate). ATP can then be broken down wherever energy is needed for processes such as movement, growth and keeping warm.
呼吸作用释放的能量暂时储存在 ATP（三磷酸腺苷）分子中。ATP 随后可以在需要能量的地方被分解，用于运动、生长和维持体温等过程。
A common misunderstanding is that respiration and breathing are the same thing. Breathing (ventilation) is the physical process of moving air in and out of the lungs. Respiration is the chemical breakdown of glucose inside cells.
常见的误解是把呼吸作用和呼吸视为同一回事。呼吸（换气）是空气进出肺部的物理过程，而呼吸作用是细胞内分解葡萄糖的化学过程。
2. Aerobic Respiration | 有氧呼吸
Aerobic respiration uses oxygen to completely break down glucose. It releases a large amount of energy and produces carbon dioxide and water as waste products. This is the most efficient way to transfer energy from glucose.
有氧呼吸利用氧气彻底分解葡萄糖。它释放大量能量，并产生二氧化碳和水作为废物。这是从葡萄糖转移能量最有效的方式。
The word equation for aerobic respiration is:
有氧呼吸的词方程式是：
glucose + oxygen → carbon dioxide + water + energy (ATP)
葡萄糖 + 氧气 → 二氧化碳 + 水 + 能量 (ATP)
Most animals and plants rely on aerobic respiration for their everyday energy needs, as long as oxygen is available. When organisms are at rest or carrying out moderate activities, aerobic respiration predominates.
只要有氧气供应，大多数动物和植物日常的能量需求都依赖于有氧呼吸。当生物处于休息状态或进行适度活动时，有氧呼吸占主导地位。
3. The Balanced Equation for Aerobic Respiration | 有氧呼吸的平衡方程式
To understand the exact chemical changes, we use a balanced symbol equation. One molecule of glucose reacts with six molecules of oxygen to give six molecules of carbon dioxide and six molecules of water.
为了理解确切的化学变化，我们使用平衡的符号方程式。一个葡萄糖分子与六个氧分子反应，生成六个二氧化碳分子和六个水分子。
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + energy (ATP)
Note that energy is released at the end – this is the ATP that cells use. The equation also shows that the number of atoms of each element is the same on both sides, which confirms the conservation of mass.
注意，最后释放的是能量 —— 也就是细胞可用的 ATP。该方程式还表明两边每种元素的原子数是相同的，验证了质量守恒定律。
You do not always have to give the balanced symbol equation in the exam unless asked, but it is excellent practice to help explain why oxygen is needed and where the carbon dioxide you breathe out originates.
除非题目明确要求，考试中不一定需要写出平衡的符号方程式，但这有助于解释为什么需要氧气以及呼出的二氧化碳从何而来的极佳训练。
4. Where Does Respiration Happen? | 呼吸作用发生在哪里？
Most of aerobic respiration takes place inside mitochondria. Mitochondria are tiny, sausage‑shaped organelles found in the cytoplasm of almost all eukaryotic cells. They contain the enzymes needed for the reactions of aerobic respiration.
大多数有氧呼吸发生在线粒体内。线粒体是几乎存在于所有真核细胞细胞质中的微小香肠状细胞器。它们含有进行有氧呼吸反应所需的酶。
Cells that require a lot of energy – such as muscle cells, sperm cells, and companion cells in phloem – have large numbers of mitochondria to meet their high energy demands.
需要大量能量的细胞 —— 比如肌肉细胞、精子细胞和韧皮部中的伴胞 —— 拥有大量的线粒体，以满足其高能量需求。
Anaerobic respiration, on the other hand, does not require mitochondria and takes place entirely in the cytoplasm. This allows cells to continue producing some ATP even when oxygen levels are low or mitochondria are absent.
另一方面，无氧呼吸不需要线粒体，完全在细胞质中进行。这使得细胞即使在氧气水平低或无线粒体的情况下也能继续产生一些 ATP。
5. Anaerobic Respiration in Animals | 动物的无氧呼吸
When oxygen cannot be supplied fast enough to muscles during vigorous exercise, cells switch to anaerobic respiration. This process breaks down glucose without oxygen, releasing much less energy per glucose molecule than aerobic respiration.
当剧烈运动时氧气无法足够快地供给肌肉，细胞便转向无氧呼吸。该过程在无氧条件下分解葡萄糖，每个葡萄糖分子释放的能量远少于有氧呼吸。
In animal cells, anaerobic respiration converts glucose into lactic acid. The word equation is:
在动物细胞中，无氧呼吸将葡萄糖转化为乳酸。词方程式为：
glucose → lactic acid + energy (ATP)
Lactic acid accumulates in muscles, causing muscle fatigue, cramp and a burning sensation. Once exercise stops, oxygen must be supplied to break down the lactic acid into carbon dioxide and water – this is called repaying the oxygen debt.
乳酸在肌肉中积累，导致肌肉疲劳、痉挛和灼烧感。一旦停止运动，必须持续供应氧气将乳酸分解为二氧化碳和水 —— 这称为偿还氧债。
Anaerobic respiration is useful because it allows muscles to keep contracting for a short time when oxygen runs out, but it cannot be sustained for long due to lactic acid build‑up and low energy yield.
无氧呼吸的益处在于，它能在氧气耗尽时让肌肉短时间内持续收缩，但由于乳酸积累和能量产出很低，无法长时间维持。
6. Anaerobic Respiration in Plants and Yeast | 植物和酵母的无氧呼吸
Plants and yeast also carry out anaerobic respiration when oxygen is limited, but the end products are different. They convert glucose into ethanol and carbon dioxide instead of lactic acid.
植物和酵母在氧气受限时也会进行无氧呼吸，但产物不同。它们将葡萄糖转化为乙醇和二氧化碳，而不是乳酸。
glucose → ethanol + carbon dioxide + energy (ATP)
This type of anaerobic respiration is known as alcoholic fermentation. It is commercially important: yeast is used in baking (where carbon dioxide makes bread rise) and in brewing (where ethanol produces alcoholic drinks).
这类无氧呼吸称为酒精发酵。它具有重要的商业意义：酵母用于烘焙（二氧化碳使面团发起来）和酿造（乙醇制造出酒精饮品）。
In waterlogged soil, plant roots may temporarily switch to anaerobic respiration. However, ethanol is also toxic to plants, so prolonged flooding can damage or kill roots.
在淹水的土壤中，植物根系可能会暂时转为无氧呼吸。然而，乙醇对植物同样有毒，因此长期浸泡会损伤甚至杀死根系。
7. Comparing Aerobic and Anaerobic Respiration | 比较有氧呼吸与无氧呼吸
The table below summarises the key differences between the two types of respiration. Both processes share the starting substrate – glucose – but differ in their requirements, products and energy yields.
下表总结了两种呼吸作用类型的关键区别。两种过程都以葡萄糖为初始底物，但在条件、产物和能量产出上有所不同。
| Feature | Aerobic respiration | Anaerobic respiration |
| Oxygen required? | Yes | No |
| Where it occurs | Mitochondria | Cytoplasm |
| Glucose breakdown | Complete | Incomplete |
| Products (animals) | CO₂ + H₂O | Lactic acid |
| Products (plants/yeast) | CO₂ + H₂O | Ethanol + CO₂ |
| Energy released | Large amount (≈ 32 ATP per glucose) | Small amount (2 ATP per glucose) |
Although aerobic respiration yields far more energy, anaerobic respiration provides an essential emergency supply when oxygen is absent and is also the basis of several food and drink industries.
虽然有氧呼吸产出的能量远多，但无氧呼吸在缺氧时提供了关键的应急能量，并且也是若干食品和饮料工业的基础。
8. The Energy Released and Its Uses | 释放的能量及其用途
The energy transferred during respiration is used for a wide range of life processes. All organisms require a constant supply of ATP to stay alive.
呼吸作用中转移的能量用于广泛的生命过程。所有生物都需要持续供应 ATP 以维持生命。
- Muscle contraction: enables movement and heartbeat. / 肌肉收缩：实现运动和心跳。
- Active transport: moves ions and molecules against a concentration gradient across cell membranes. / 主动运输：逆浓度梯度跨细胞膜移动离子和分子。
- Cell division and growth: supplies energy for making new cells and tissues. / 细胞分裂和生长：为制造新细胞和组织提供能量。
- Maintaining body temperature: in birds and mammals, heat released by respiration helps keep body temperature constant (thermoregulation). / 维持体温：在鸟类和哺乳动物中，呼吸作用释放的热量有助于保持体温恒定（温度调节）。
- Biosynthesis: building large molecules like proteins, lipids and nucleic acids. / 生物合成：构建蛋白质、脂质和核酸等大分子。
- Bioluminescence and nerve impulses: some organisms use ATP for light production; all nervous systems rely on ATP for transmitting impulses. / 生物发光和神经冲动：有些生物体利用 ATP 发光；所有神经系统依赖 ATP 传递冲动。
In plants, respiration provides the energy needed for mineral uptake by roots and for converting sugars into starch, cellulose and other compounds required for growth.
在植物中，呼吸作用提供根部吸收矿物质所需的能量，以及将糖转化为淀粉、纤维素和其他生长所需化合物的能量。
9. Response to Exercise: Oxygen Debt | 运动反应：氧债
During intense exercise, the demand for oxygen surpasses the supply rate. Muscles carry out anaerobic respiration, producing lactic acid. The amount of extra oxygen needed after exercise to remove this lactic acid is called the oxygen debt.
在剧烈运动期间，对氧气的需求超过了供给速度。肌肉进行无氧呼吸，产生乳酸。运动后需要用来消除这些乳酸的额外氧气量，称为氧债。
Oxygen debt is repaid by continuing to breathe deeply and rapidly after exercise. The extra oxygen travels to the liver, where lactic acid is converted back into glucose or oxidised to carbon dioxide and water. Some lactic acid may also be converted into glycogen for storage.
氧债通过运动后持续深而快的呼吸来偿还。额外的氧气被输送到肝脏，在那里乳酸被转化回葡萄糖，或被氧化为二氧化碳和水。部分乳酸也可能转化为糖原储存起来。
Measuring oxygen debt is complex, but a simple indicator is the elevated breathing rate and heart rate that persists after stopping strenuous activity. This physiological response helps return the body to its resting state and remove toxic metabolites.
测量氧债比较复杂，但一个简单的指标是在停止剧烈运动后持续较快的呼吸频率和心率。这种生理反应有助于身体恢复到静息状态并清除有毒代谢产物。
10. Investigating Respiration (Practical) | 探究呼吸作用（实验）
You need to understand how respiration can be investigated experimentally. A common method uses a respirometer to measure oxygen consumption by living organisms, such as germinating seeds or small insects.
你需要了解如何用实验探究呼吸作用。一种常见方法是使用呼吸计测量活生物体（例如发芽的种子或小昆虫）的耗氧量。
A simple respirometer consists of a sealed tube containing the organism, connected to a manometer or coloured liquid in a capillary tube. Soda lime or potassium hydroxide solution is added to absorb carbon dioxide produced. As the organism respires, it uses oxygen, and the decrease in gas volume causes the liquid to move along the tube.
简单的呼吸计由装生物体的密封管组成，连接到一个测压计或毛细管中的有色液体。加入碱石灰或氢氧化钾溶液以吸收产生的二氧化碳。当生物体呼吸时，它消耗氧气，气体体积减少导致液体沿管移动。
Control experiments must be set up in identical conditions but without the living organism, to account for changes in temperature and atmospheric pressure. The distance moved by the liquid over a fixed time can be used to calculate the rate of oxygen uptake.
必须设置相同条件但无活生物体的对照实验，以排除温度和大气压力变化的影响。液体在固定时间内移动的距离可用于计算氧气摄取速率。
Another practical involves detecting carbon dioxide produced by respiration: pass exhaled air (or air from germinating seeds) through limewater; it turns cloudy due to the formation of calcium carbonate. A hydrogencarbonate indicator can also be used, turning from red to yellow in the presence of carbon dioxide.
另一个实验涉及检测呼吸作用产生的二氧化碳：将呼出的气体（或来自发芽种子的空气）通过石灰水；由于碳酸钙的形成，石灰水变浑浊。也可以使用碳酸氢盐指示剂，在二氧化碳存在下由红变黄。
Temperature probes or thermometers can show that respiration is exothermic: a vacuum flask with germinating seeds will show a temperature rise compared to boiled, dead seeds used as a control.
温度探针或温度计可显示呼吸作用是放热的：与作为对照的煮过的死种子相比，装有发芽种子的保温瓶会显示温度升高。
11. Key Definitions Summary | 关键定义总结
- Respiration: an exothermic chemical reaction that transfers energy from glucose in all living cells. / 呼吸作用：一种在所有活细胞中从葡萄糖转移能量的放热化学反应。
- Aerobic respiration: respiration using oxygen, producing CO₂ and H₂O, releasing lots of energy. / 有氧呼吸：使用氧气的呼吸作用，产生二氧化碳和水，释放大量能量。
- Anaerobic respiration: respiration without oxygen, producing lactic acid (animals) or ethanol and CO₂ (plants/yeast), releasing much less energy. / 无氧呼吸：不需要氧气的呼吸作用，产生乳酸（动物）或乙醇和二氧化碳（植物/酵母），释放的能量少得多。
- ATP: adenosine triphosphate, the molecule that stores and transfers energy in cells. / ATP：三磷酸腺苷，在细胞内储存并转移能量的分子。
- Oxygen debt: the extra oxygen needed after anaerobic respiration to break down lactic acid. / 氧债：无氧呼吸后分解乳酸所需的额外氧气。
- Fermentation: another name for anaerobic respiration in yeast and some microorganisms. / 发酵：酵母和某些微生物中无氧呼吸的别称。
- Mitochondria: organelles where most aerobic respiration takes place. / 线粒体：进行大部分有氧呼吸的细胞器。
12. Exam Tips | 考试技巧
Always state clearly that respiration is an exothermic process – the word ‘exothermic’ often gains a mark. Never confuse respiration with photosynthesis or with breathing; examiners deliberately set questions to test this distinction.
始终明确说明呼吸作用是放热过程 —— “放热”一词常常能得分。永远不要把呼吸作用与光合作用或呼吸（换气）混淆；考官会刻意设置题目来测试这种区分。
When writing equations, always include ‘energy’ or ‘ATP’ on the product side. For anaerobic respiration in animals, you only need to write ‘lactic acid’ – not ‘lactic acid + CO₂’. For plants and yeast, remember ethanol and CO₂.
书写方程式时，务必在产物一侧写上“能量”或“ATP”。对于动物的无氧呼吸，只需写“乳酸” —— 不是“乳酸 + 二氧化碳”。对于植物和酵母，记住是乙醇和二氧化碳。
Use the correct terminology: ‘oxygen debt’, not ‘owing oxygen’. Be prepared to interpret respirometer data and explain why soda lime is used (to absorb CO₂ so that any change in gas volume is due to oxygen uptake only).
使用正确的术语：“氧债”（oxygen debt），而不是“欠氧”。准备好解读呼吸计数据，并解释为什么使用碱石灰（吸收二氧化碳，因而气体体积的任何变化仅由氧气摄取引起）。
In longer‑answer questions, link the type of respiration to the situation: at rest, aerobic; during a sprint, anaerobic builds up lactic acid, leading to oxygen debt. Connect energy released to specific processes like muscle contraction or active transport.
在较长答案的题目中，将呼吸作用类型与情境关联起来：休息时进行有氧呼吸；短跑冲刺时无氧呼吸导致乳酸积累，进而产生氧债。将释放的能量与具体过程连接，如肌肉收缩或主动运输。
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