Formula Summary Handbook | IGCSE OCR 生物：公式汇总手册

📚 Formula Summary Handbook | IGCSE OCR 生物：公式汇总手册

This handbook compiles essential formulae needed for IGCSE Biology, following OCR specification requirements. Understanding and being able to apply these equations is crucial for calculations in topics such as cell structure, enzymes, transport in humans, photosynthesis, ecosystems and more. Memorise the forms and practise unit conversions.

本手册汇总了 IGCSE 生物学所需的关键公式，依据 OCR 考试大纲要求。理解并能运用这些方程对于细胞结构、酶、人体运输、光合作用、生态系统等主题的计算至关重要。请熟记公式形式并练习单位换算。

1. Magnification Calculations | 放大倍数计算

Magnification is a measure of how much larger a microscope image appears compared to the real size of the specimen. The fundamental formula is:

Magnification = Image size ÷ Actual size

放大倍数是衡量显微镜图像比标本实际尺寸大多少的指标。基本公式为：

放大倍数 = 图像大小 ÷ 实际大小

To use the formula correctly, both image size and actual size must be in the same unit. Typically, actual sizes are given in millimetres or micrometres, so you must convert appropriately. If you need the actual size, rearrange to:

Actual size = Image size ÷ Magnification

正确使用公式时，图像大小和实际大小必须采用相同单位。通常实际大小以毫米或微米给出，因此你需要适当换算。如果需要计算实际大小，可以变式为：

实际大小 = 图像大小 ÷ 放大倍数

Conversely, the image size can be calculated by multiplying the magnification by the actual size:

Image size = Magnification × Actual size

反过来，图像大小也能通过放大倍数乘实际大小得出：

图像大小 = 放大倍数 × 实际大小

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2. Rate of Reaction | 反应速率

The rate of a biological process—such as enzyme activity, respiration, or photosynthesis—can be expressed as a change in a measured quantity over time. The general formula is:

Rate = Change in quantity ÷ Time taken

生物过程（如酶活性、呼吸作用或光合作用）的速率可以用单位时间内测量量的变化来表示。通用公式为：

速率 = 变化量 ÷ 所用时间

For example, if an enzyme experiment produces 12 cm³ of oxygen in 4 minutes, the rate is 12 ÷ 4 = 3 cm³ min¼. During respiration, rate can be measured by the volume of CO&sub2; produced per unit time.

例如，若酶实验在 4 分钟内产生 12 cm³ 氧气，则速率为 12 ÷ 4 = 3 cm³ min⁻¹。在呼吸作用中，速率可通过单位时间产生的 CO₂ 体积来衡量。

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3. Percentage Change | 百分比变化

In osmosis experiments or when comparing growth, you often need to calculate the percentage change in mass or length. The formula is:

Percentage change = ((Final value − Initial value) ÷ Initial value) × 100%

在渗透实验或比较生长状况时，常需计算质量或长度的百分比变化。公式为：

百分比变化 = ((最终值 − 初始值) ÷ 初始值) × 100%

A positive result indicates an increase; a negative result indicates a decrease. This formula is essential for analysing potato cylinder mass changes in different sugar solutions.

结果为正值表示增加，负值表示减少。该公式对于分析马铃薯条在不同糖溶液中质量变化至关重要。

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4. Photosynthesis Rate and Inverse Square Law | 光合作用速率与平方反比定律

The rate of photosynthesis is often measured by the volume of oxygen released per minute. An important relationship when varying light distance is the inverse square law:

Light intensity ∝ 1 ÷ (Distance)²

光合作用速率常用每分钟释放的氧气体积来衡量。改变光源距离时的一个重要关系是平方反比定律：

光强度 ∝ 1 ÷ (距离)²

This means that doubling the distance between the lamp and the pondweed reduces the light intensity to one quarter, which directly affects the photosynthesis rate. You can use the rate formula to compare values.

这意味着将灯和水草之间的距离加倍会使光强度降至四分之一，直接影响光合作用速率。你可以用速率公式来比较数值。

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5. Cardiac Output | 心输出量

Cardiac output is the volume of blood pumped by one ventricle per minute. It depends on heart rate and stroke volume:

Cardiac output (cm³ min⁻¹) = Heart rate (beats min⁻¹) × Stroke volume (cm³)

心输出量是一侧心室每分钟泵出的血液体积。它取决于心率和每搏输出量：

心输出量 (cm³ min⁻¹) = 心率 (次 min⁻¹) × 每搏输出量 (cm³)

For a resting adult, typical values might be 70 beats min⁻¹ and 70 cm³ stroke volume, giving a cardiac output of about 4900 cm³ min⁻¹. During exercise, both can increase.

对一个静息成人来说，典型值为心率 70 次/分，每搏输出量 70 cm³，心输出量约为 4900 cm³ min⁻¹。

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