📚 A-Level WJEC Biology Formula Summary Handbook | A-Level WJEC 生物公式汇总手册
This comprehensive handbook compiles the essential formulae and quantitative relationships required for A-Level WJEC Biology. Mastery of these equations is vital for calculations across microscopy, physiology, ecology and biochemistry, and will support your success in both written examinations and practical assessments.
这本综合手册汇编了 A-Level WJEC 生物学所需的关键公式和定量关系。掌握这些方程式对于显微镜学、生理学、生态学和生物化学中的计算至关重要，并将助力您在笔试和实践评估中取得成功。
1. Microscopy and Magnification | 显微镜与放大倍数
Magnification is the ratio between the size of an image and the real size of the object. The fundamental equation is:
放大倍数是图像大小与物体实际大小之间的比值。基本公式为：
Magnification = Image size / Actual size
This relationship can be rearranged depending on the unknown: Actual size = Image size / Magnification, or Image size = Actual size × Magnification.
该关系可根据未知量进行变形：实际大小 = 图像大小 / 放大倍数，或 图像大小 = 实际大小 × 放大倍数。
All quantities must be expressed in the same units before calculation. Typical units are millimetres (mm) and micrometres (µm). Remember that 1 mm = 1000 µm. A scale bar on a micrograph can be measured and used to determine actual size or magnification.
计算前所有量必须用相同单位表示。常用单位为毫米 (mm) 和微米 (µm)。请记住 1 mm = 1000 µm。显微照片上的比例尺可以通过测量，用以确定实际大小或放大倍数。
In WJEC exam contexts, you will often be presented with an electron micrograph or a light microscope image and a scale bar. Measure the scale bar length, convert to appropriate units, and apply the formula accurately.
在 WJEC 考试情境中，经常会给出电子显微照片或光学显微镜图像及比例尺。测量比例尺长度，转换为合适的单位，并准确应用公式。
2. Haemocytometer Calculations | 血球计数板细胞计数
A haemocytometer (improved Neubauer) is used to estimate cell concentration in a liquid culture. The counting grid has a known depth (0.1 mm) and each large square covers an area of 1 mm², giving a volume of 0.1 mm³, equivalent to 10⁻⁴ mL.
血球计数板（改进型诺伊鲍尔）用于估算液体培养物中的细胞浓度。计数网格具有已知深度（0.1 mm），每个大方格的面积为 1 mm²，体积为 0.1 mm³，相当于 10⁻⁴ mL。
The general formula for cell concentration is:
细胞浓度的通用公式为：
Cells per mL = (Average count per large square) × Dilution factor × 10⁴
To obtain the average count per large square, count cells in several large squares (e.g., five) and divide the total by the number of squares. The dilution factor accounts for any dilution of the original sample (e.g., 10-fold dilution gives DF = 10). Multiplying by 10⁴ converts the volume from 0.1 mm³ to 1 cm³ (i.e., 1 mL).
为获得每个大方格的平均计数，需计数多个大方格（例如五个）中的细胞，并将总数除以方格数。稀释因子用于校正原始样品的任何稀释（例如，10 倍稀释时 DF = 10）。乘以 10⁴ 可将体积从 0.1 mm³ 转换为 1 cm³（即 1 mL）。
For viable cell counts with trypan blue, only unstained (living) cells are counted. Ensure you use consistent counting rules (e.g., count cells touching the top and left borders, ignore those touching bottom and right) to avoid bias.
使用台盼蓝进行活细胞计数时，仅计数未染色（活）的细胞。确保采用一致的计数规则（例如，计数接触上边界和左边界的细胞，忽略接触下边界和右边界的细胞），以避免偏差。
3. Dilution Series and Standard Curves | 稀释系列与标准曲线
Serial dilutions are produced by progressively diluting a stock solution to create a range of known concentrations. The relationship between concentration and volume is given by:
连续稀释是通过逐步稀释储备液，得到一系列已知浓度。浓度和体积之间的关系为：
C₁V₁ = C₂V₂
where C₁ and V₁ are the concentration and volume of the stock, and C₂ and V₂ are the concentration and volume of the final diluted solution. This equation ensures the number of moles of solute remains constant during dilution.
其中 C₁ 和 V₁ 是储备液的浓度和体积，C₂ 和 V₂ 是最终稀释溶液的浓度和体积。该等式确保了稀释过程中溶质的摩尔数保持不变。
A standard curve is constructed by plotting absorbance (or another measurable response) against known concentrations. The concentration of an unknown sample can then be read from the graph. In WJEC practicals, this technique is often used with a colorimeter and a dilution series of a known substance.
标准曲线通过将吸光度（或其它可测量响应）相对于已知浓度作图而构建。未知样品的浓度可从图表中读取。在 WJEC 实践操作中，此技术常与比色计和已知物质的稀释系列结合使用。
When preparing serial dilutions, it is good practice to mix thoroughly between steps and to use the same diluent for all dilutions to minimise matrix effects.
在制备连续稀释液时，良好做法是在各步骤之间充分混合，并对所有稀释使用相同的稀释剂，以尽量减少基质效应。
4. Water Potential (Ψ) | 水势 (Ψ)
Water potential determines the direction of water movement across a partially permeable membrane. It is expressed as the sum of solute potential (Ψₛ) and pressure potential (Ψₚ):
水势决定了水分通过半透膜的运动方向。它表示为溶质势 (Ψₛ) 和压力势 (Ψₚ) 的总和：
Ψ = Ψₛ + Ψₚ
Solute potential is always zero or negative because dissolved solutes reduce the free energy of water. In dilute solutions, Ψₛ approaches 0; in concentrated solutions, Ψₛ is strongly negative. Pressure potential is usually positive in living plant cells (turgor pressure) but can be zero or negative in xylem under tension.
溶质势始终为零或负值，因为溶解的溶质降低了水的自由能。在稀溶液中，Ψₛ 接近 0；在浓溶液中，Ψₛ 为强负值。压力势在活植物细胞中通常为正值（膨压），但在张力下的木质部中可为零或负值。
Water moves from regions of higher (less negative) water potential to regions of lower (more negative) water potential. Pure water has a water potential of 0 MPa. In WJEC exams, you may be asked to predict water movement based on given Ψ values.
水分从水势较高（负值较小）的区域流向水势较低（负值较大）的区域。纯水的水势为 0 MPa。在 WJEC 考试中，可能要求根据给定的 Ψ 值预测水分的移动方向。
5. Respiratory Quotient (RQ) | 呼吸商 (RQ)
The respiratory quotient is a dimensionless number that indicates the substrate being respired and the efficiency of gas exchange. It is defined as:
呼吸商是一个无量纲数值，能指示正在被呼吸的呼吸底物以及气体交换的效率。其定义为：
RQ = CO₂ produced / O₂ consumed
When carbohydrates are the sole respiratory substrate, the RQ is approximately 1.0. Lipid respiration consumes more oxygen relative to carbon dioxide produced, yielding an RQ of about 0.7. Proteins give an RQ around 0.9. Intermediate values suggest mixed substrate usage.
当唯一呼吸底物为碳水化合物时，RQ 约为 1.0。脂质呼吸相对于产生的二氧化碳消耗更多氧气，产生的 RQ 约为 0.7。蛋白质的 RQ 约为 0.9。中间数值表明混合底物的使用。
RQ can also be influenced by anaerobic respiration or by cellular processes that produce or consume acids. In respirometer experiments, the RQ is calculated by measuring the volume of oxygen taken up and the volume of carbon dioxide released, often using a manometer and potassium hydroxide to absorb CO₂.
RQ 也会受无氧呼吸或产生/消耗酸的细胞过程影响。在呼吸计实验中，RQ 通过测量吸收的氧气体积和释放的二氧化碳体积来计算，通常使用压力计和氢氧化钾吸收 CO₂。
6. Photosynthesis: Net Photosynthesis and Efficiency | 光合作用：净光合作用与效率
Gross photosynthesis is the total rate of carbohydrate production by the Calvin cycle, whereas net photosynthesis is the gain after respiratory losses have been subtracted. The relationship is:
总光合作用是卡尔文循环产生碳水化合物的总速率，而净光合作用是减去呼吸损耗后的净增加量。关系式为：
Net photosynthesis = Gross photosynthesis – Respiration
This can also be expressed in terms of oxygen production: net O₂ evolution = gross O₂ production – O₂ consumed in respiration. The rate of photosynthesis can be measured by the change in oxygen or carbon dioxide concentration, or by the uptake of carbon‑14.
这也可用氧气产量表示：净 O₂ 释放量 = 总 O₂ 产量 – 呼吸消耗的 O₂。光合作用速率可通过氧气或二氧化碳浓度的变化，或碳‑14 的吸收来测量。
Photosynthetic efficiency is the percentage of light energy falling on a leaf that is converted into chemical energy. A simple efficiency formula is:
光合效率是照射在叶片上的光能转化为化学能的百分比。一个简单的效率公式为：
Efficiency = (Energy captured in glucose / Light energy absorbed) × 100%
Crop plants typically achieve efficiencies of 1–2% under field conditions, with the theoretical maximum being around 6% for C₃ plants. Efficiency is reduced by factors such as photorespiration, light saturation, and reflection.
在大田条件下，作物通常达到 1–2% 的效率，C₃ 植物的理论最大值约为 6%。光呼吸、光饱和和反射等因素会降低效率。
7. Ecological Efficiency and Energy Transfer | 生态效率与能量传递
Energy transfer between trophic levels is never 100% efficient. The percentage of energy transferred from one trophic level to the next is calculated as:
营养级之间的能量传递效率从未达到 100%。从一个营养级传递到下一个营养级的能量百分比计算如下：
Efficiency = (Energy available in next trophic level / Energy available in current trophic level) × 100%
In most ecosystems, ecological efficiency ranges from 10% to 20%. The remainder is lost as heat from respiration, uneaten parts, and waste products.
在大多数生态系统中，生态效率范围为 10% 到 20%。其余能量以呼吸热、未被取食的部分和废物等形式散失。
For primary producers, net primary productivity (NPP) is the energy that remains after respiratory losses have been subtracted from gross primary productivity (GPP):
对于初级生产者，净初级生产力 (NPP) 是指从总初级生产力 (GPP) 中扣除呼吸损耗后剩余的能量：
NPP = GPP –
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