Year 11 Cambridge Biology: Key Points for Practical Assessment | Year 11 剑桥生物：实验/实践考核要点

📚 Year 11 Cambridge Biology: Key Points for Practical Assessment | Year 11 剑桥生物：实验/实践考核要点

In the Cambridge IGCSE Biology practical assessment (Papers 5 and 6), you are tested on your ability to carry out experiments, record observations, handle data, and evaluate procedures. This article highlights the key experimental skills and common investigations you must master to excel in the practical component.

在剑桥 IGCSE 生物实践考核（试卷 5 和 6）中，考查你进行实验、记录观察、处理数据和评估步骤的能力。本文重点介绍你必须掌握的关键实验技能和常见研究，以在实践部分取得优异成绩。

1. Understanding the Practical Exam Format | 理解实验考试形式

Papers 5 and 6 both assess practical skills, but Paper 5 is a hands-on laboratory test while Paper 6 is a written alternative to practical. Both require you to interpret experimental set-ups, record readings, and answer questions on familiar investigations.

试卷 5 和 6 都评估实践技能，但试卷 5 是动手实验考试，试卷 6 则是实验替代笔试。两者都要求你解读实验装置、记录读数并回答关于熟悉探究的问题。

The questions typically involve microscope work, food tests, enzyme reactions, osmosis, and photosynthesis experiments. You must know how to plan a fair test, control variables, and present results in tables and graphs.

题目通常涉及显微镜操作、食物测试、酶反应、渗透作用和光合作用实验。你必须懂得如何设计公平测试、控制变量，并以表格和图表展示结果。

Time management is crucial; read all instructions carefully before starting. Always note the number of marks allocated to each part to guide the depth of your answer.

时间管理至关重要；在开始前仔细阅读所有说明。注意每部分的分值，以指导答题的详尽程度。

2. Using a Microscope and Biological Drawing | 使用显微镜与生物绘图

You may be asked to prepare a temporary slide, focus under a microscope, and make a labelled drawing of cells or tissues. Use only a sharp HB pencil for drawings, and draw clear, continuous outlines without shading or colouring.

你可能会被要求制作临时装片、用显微镜聚焦，并绘制带标注的细胞或组织图。绘图仅用削尖的 HB 铅笔，画出清晰、连续的轮廓，不要加阴影或涂色。

All label lines must be straight, drawn with a ruler, and must touch the structure being labelled. Write labels horizontally and include the magnification if known. The drawing should occupy at least half of the space provided.

所有标注线必须用尺子画直，并且要接触到所标注的结构。标签应水平书写，如知道放大倍数要注明。绘图应至少占据所给空间的一半。

Do not draw individual cells if the specimen is a tissue with many cells – instead, draw a few representative cells and indicate that the pattern continues. Always include a title that states what the drawing shows and the magnification.

如果标本是由许多细胞构成的组织，不要画出所有细胞，而是画几个代表性细胞并表明结构延续。始终撰写标题，说明所画内容和放大倍数。

3. Food Tests and Biochemical Assays | 食物测试与生化检测

Common food tests include Benedict’s test for reducing sugars, iodine test for starch, Biuret test for proteins, and the ethanol emulsion test for fats. You must know the reagents, procedures, and expected positive results.

常见的食物测试包括本氏试验（还原糖）、碘液试验（淀粉）、双缩脲试验（蛋白质）和乙醇乳化试验（脂肪）。你必须知道试剂、操作步骤和预期的阳性结果。

For the Benedict’s test, add an equal volume of Benedict’s solution to the food solution and heat in a water bath; a brick-red precipitate indicates reducing sugar. The iodine test turns blue-black in the presence of starch.

进行本氏试验时，向食物溶液中加入等体积的本氏试剂并在水浴中加热；出现砖红色沉淀表明有还原糖。碘液测试遇淀粉呈蓝黑色。

The Biuret test requires adding sodium hydroxide solution and then a few drops of copper sulfate solution; a purple or violet colour shows protein. For fats, shake the sample with ethanol, then pour into water; a cloudy white emulsion confirms lipids.

双缩脲试验需要先加入氢氧化钠溶液，再滴加几滴硫酸铜溶液；出现紫色表明有蛋白质。测试脂肪时，将样品与乙醇一起摇动，然后倒入水中；出现混浊的白色乳液即证实有脂质。

In the practical exam, you must describe the colour changes accurately and compare results with a control using water. Also understand half-quantitative results, such as different intensities of colour indicating different concentrations.

在实践考试中，你必须准确描述颜色变化，并与用水做的对照进行比较。还要理解半定量结果，例如颜色深浅不同代表不同浓度。

4. Investigating Enzyme Action | 探究酶的作用

Enzyme experiments often investigate the effect of temperature or pH on the rate of reaction, such as the breakdown of starch by amylase or hydrogen peroxide by catalase. You need to identify independent, dependent, and control variables.

酶实验经常探究温度或 pH 对反应速率的影响，例如淀粉酶分解淀粉或过氧化氢酶分解过氧化氢。你必须识别自变量、因变量和受控变量。

In a typical amylase–starch investigation, mix amylase solution with starch suspension at a given temperature, and take samples every 30 seconds to test with iodine on a spotting tile until the blue-black colour disappears. The time taken for starch breakdown indicates enzyme activity.

在典型的淀粉酶-淀粉探究中，将淀粉酶溶液与淀粉悬浮液在指定温度混合，每隔 30 秒取样并用碘液在点滴板上测试，直到蓝黑色消失。淀粉完全分解所需的时间反映酶活性。

You should be able to explain why the reaction rate changes with temperature or pH in terms of kinetic energy, enzyme shape, and denaturation. Always include a suitable control without the enzyme.

你应能够从动能、酶的形状和变性

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