📚 IGCSE Biology: Unit Test Papers | IGCSE生物：单元测试卷
Unit test papers are an essential tool for IGCSE Biology revision. They break down the syllabus into manageable topics, allowing you to test your knowledge and identify weak areas before the final exam. This article provides a series of sample questions from key units, each followed by a clear answer and explanation. By working through these targeted exercises, you will strengthen your understanding of fundamental concepts and sharpen your exam technique.
单元测试卷是IGCSE生物复习的重要工具。它们将教学大纲分解为易于掌握的主题，帮助你在期末考试前检测知识掌握情况并找出薄弱环节。本文提供了一系列来自核心单元的样题，每道题都附有清晰的答案与解析。通过这些针对性练习，你将加深对基本概念的理解，并提升应试技巧。
1. Cells and Cell Organisation | 细胞与细胞组织
A typical unit test on cells will ask you to compare plant and animal cells, identify organelles, and explain how cells are organised into tissues, organs, and systems. Here is a common question:
关于细胞的单元测试通常会要求你比较植物和动物细胞，识别细胞器，并解释细胞如何组织成组织、器官和系统。下面是一道常见题：
Question: State two structural differences between a typical plant cell and an animal cell. (2 marks)
问题： 陈述一个典型的植物细胞与一个动物细胞在结构上的两个不同之处。(2分)
Answer:
- Plant cells have a rigid cell wall made of cellulose, whereas animal cells do not have a cell wall.
- Plant cells usually contain chloroplasts for photosynthesis; animal cells lack chloroplasts.
Also acceptable: Plant cells have a large permanent vacuole, while animal cells have small, temporary vacuoles or none at all.
答案：
- 植物细胞有由纤维素组成的坚硬细胞壁，而动物细胞没有细胞壁。
- 植物细胞通常含有进行光合作用的叶绿体；动物细胞则没有叶绿体。
也可接受：植物细胞有一个大而永久的液泡，而动物细胞只有小且临时的液泡或没有液泡。
2. Movement Across Membranes | 物质跨膜运输
Questions in this unit often focus on diffusion, osmosis, and active transport. You may be asked to describe the process and give an example from living organisms.
这个单元的题目通常关注扩散、渗透和主动运输。你可能会被要求描述过程并给出生物体中的例子。
Question: Explain how root hair cells absorb mineral ions from the soil. (3 marks)
问题： 解释根毛细胞如何从土壤中吸收矿物质离子。(3分)
Answer: Root hair cells absorb mineral ions by active transport. The concentration of mineral ions inside the cell is higher than in the soil, so the ions must move against the concentration gradient. This process requires energy from respiration, which is provided by the many mitochondria present in the root hair cell. Specific carrier proteins in the cell membrane use this energy to transport the ions into the cell.
答案： 根毛细胞通过主动运输吸收矿物质离子。细胞内的离子浓度高于土壤中的浓度，因此离子必须逆浓度梯度移动。这个过程需要呼吸作用提供的能量，由根毛细胞中丰富的线粒体提供。细胞膜上的特异载体蛋白利用这些能量将离子转运到细胞内。
3. Enzymes | 酶
Enzyme questions often test your understanding of the lock-and-key hypothesis, factors affecting enzyme activity, and simple experiments.
酶相关题目经常考查你对锁钥假说、影响酶活性因素以及简单实验的理解。
Question: The graph below shows the effect of increasing temperature on the rate of an enzyme-catalysed reaction. Explain the shape of the curve, referring to the terms 'kinetic energy' and 'denaturation'. (4 marks)
问题： 下图显示了温度升高对酶催化反应速率的影响。用“动能”和“变性”这两个术语解释曲线的形状。(4分)
Answer: As temperature increases, the kinetic energy of the enzyme and substrate molecules increases. They move faster and collide more frequently, forming more enzyme-substrate complexes. This causes the rate of reaction to rise up to the optimum temperature (around 37 °C for many human enzymes). Beyond the optimum, the high temperature begins to break the bonds that hold the enzyme's tertiary structure. The active site loses its specific shape. The enzyme becomes denatured, the substrate can no longer fit, and the reaction rate falls sharply.
答案： 随着温度升高，酶和底物分子的动能增加。它们运动加快，碰撞更频繁，形成更多的酶-底物复合物。这使得反应速率上升，直到最适温度（许多人体酶约为37 °C）。超过最适温度后，高温开始破坏维持酶三级结构的化学键。活性位点失去其特定形状，酶发生变性，底物不再能与之契合，因此反应速率急剧下降。
4. Plant Nutrition (Photosynthesis) | 植物营养（光合作用）
Test items often require you to write the word or balanced chemical equation for photosynthesis and discuss limiting factors.
试题常要求你写出光合作用的文字方程式或平衡化学方程式，并讨论限制因素。
Question: Write the balanced chemical equation for photosynthesis and state three factors that can limit the rate of photosynthesis in a greenhouse. (4 marks)
问题： 写出光合作用的平衡化学方程式，并说明在温室中可能限制光合作用速率的三个因素。(4分)
6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂
Answer: The balanced equation is as shown above (light and chlorophyll are required but are not written as reactants/products). Three limiting factors are: light intensity, carbon dioxide concentration, and temperature. If any one of these is in short supply, the rate of photosynthesis is limited, even if the other factors are present in abundance.
答案： 平衡方程式如上所示（需要光和叶绿素，但不作为反应物或生成物写出）。三个限制因素是：光照强度、二氧化碳浓度和温度。如果其中任何一个供应不足，即使其他因素很充足，光合作用速率也会受到限制。
5. Human Nutrition and Digestion | 人体营养与消化
Expect questions on digestive enzymes, their source, substrate, and products, as well as the role of bile.
可能考查消化酶、它们的来源、底物和产物，以及胆汁的作用。 Published by TutorHao | IGCSE Biology Revision Series | aleveler.com
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