📚 Communicable Diseases & Disease Prevention Exam Practice | 传染性疾病与疾病预防真题精练
This exam practice article focuses on Topic 4.1 Communicable Diseases and Disease Prevention, a core area in A-level Biology. Use these typical exam-style questions to test your understanding, master key mark-scoring techniques, and identify common pitfalls. Each section presents a representative question, followed by a model answer and essential examiner tips to help you secure top marks.
本真题精练围绕 A-level 生物中 4.1 传染性疾病与疾病预防这一核心主题展开。通过典型考试风格的问题，帮助你检验理解程度、掌握高分答题技巧并识别常见失分点。每个小节呈现一道代表性真题，并配有模型答案和关键考官提示，助你稳拿高分。
1. Pathogen Classification and Structure | 病原体分类与结构
Exam question: ‘Compare and contrast the structure of a typical bacterium and a virus. (4 marks)’
真题：”比较并对比典型细菌和病毒的结构。（4分）”
Model answer: Bacteria are prokaryotic cells with a cell wall made of peptidoglycan, a cell membrane, cytoplasm, 70S ribosomes, circular DNA and sometimes small plasmids. They have no nucleus but a nucleoid region. Viruses are acellular; they consist only of a protein capsid enclosing nucleic acid (DNA or RNA) – sometimes have an envelope derived from host cell membrane. They lack cytoplasm, ribosomes and metabolic enzymes. Whereas bacteria can carry out independent metabolism and reproduction, viruses must hijack host cellular machinery.
模型答案：细菌是原核细胞，具有肽聚糖细胞壁、细胞膜、细胞质、70S 核糖体、环状 DNA 以及有时存在的小质粒。它们没有细胞核，但有一个拟核区域。病毒是非细胞结构，仅由蛋白质衣壳包裹核酸（DNA 或 RNA）组成——有时还有来自宿主细胞膜的包膜。它们缺少细胞质、核糖体和代谢酶。细菌可独立代谢和繁殖，而病毒必须劫持宿主的细胞机器。
Examiner tip: For comparison questions, use linking words such as ‘whereas’ or ‘however’, and highlight structural differences (e.g., ribosome presence, genetic material type). Do not simply list facts without relating the two entities.
考官提示：遇到比较题，要使用’whereas’或’however’等连接词，突出结构差异（如核糖体的有无、遗传物质类型）。不要只罗列事实而不关联两者。
2. Modes of Transmission | 传播方式
Exam question: ‘Explain how the malarial parasite is transmitted to humans and suggest two methods of controlling its spread. (4 marks)’
真题：”解释疟原虫如何传播给人类，并提出两种控制传播的方法。（4分）”
Model answer: The parasite (Plasmodium) is transmitted by female Anopheles mosquitoes. When an infected mosquito takes a blood meal, it injects sporozoites into the human’s bloodstream. These travel to the liver, multiply, and later infect red blood cells. Control methods: (1) using insecticide-treated bed nets to prevent mosquito bites at night; (2) draining stagnant water to reduce mosquito breeding sites. Other acceptable answers include indoor residual spraying and antimalarial drugs for prophylaxis.
模型答案：疟原虫（Plasmodium）通过雌性按蚊传播。当受感染的蚊子吸血时，它将子孢子注入人体血液。这些子孢子移至肝脏进行增殖，然后感染红细胞。控制方法：（1）使用经杀虫剂处理的蚊帐以避蚊叮咬；（2）排干积水减少蚊子滋生地。其他可接受的答案还有室内滞留喷洒和预防性抗疟药物。
Examiner tip: Clearly name the vector and the infective stage (sporozoite). Link control methods directly to the transmission route—for example, nets block physical contact, while draining water interrupts the life cycle.
考官提示：明确说出传播媒介和感染阶段（子孢子）。将控制方法直接与传播途径关联起来——例如，蚊帐阻断物理接触，排水则阻断其生活史。
3. Non-Specific Defences | 非特异性防御
Exam question: ‘Describe two non-specific defence mechanisms in humans and explain how each prevents entry or spread of pathogens. (4 marks)’
真题：”描述人体内的两种非特异性防御机制，并解释每种机制如何阻止病原体进入或扩散。（4分）”
Model answer: (1) The skin acts as a physical barrier – it has a tough, impermeable keratinised outer layer that pathogens cannot easily penetrate. Sebum and sweat lower pH and contain lysozyme, which destroys bacterial cell walls. (2) The mucociliary escalator in the trachea traps inhaled pathogens in mucus secreted by goblet cells, and cilia beat to sweep the mucus up to the throat where it is swallowed and destroyed by stomach acid.
模型答案：（1）皮肤作为物理屏障——其坚韧、不可渗透的角化外层使得病原体难以穿透。皮脂和汗液降低 pH 值并含有溶菌酶，可破坏细菌细胞壁。（2）气管中的黏膜纤毛系统通过杯状细胞分泌的黏液粘住吸入的病原体，纤毛摆动将黏液推至咽喉，之后被吞咽并被胃酸杀灭。
Examiner tip: Be precise with terminology like ‘keratinised’ and ‘goblet cells’. Always explain how the structure relates to function – merely stating ‘skin is a barrier’ will not earn full marks.
考官提示：准确使用像’角化’和’杯状细胞’这样的术语。始终说明结构如何与功能相关联——仅仅说’皮肤是屏障’无法拿全分。
4. Phagocytosis and Antigen Presentation | 吞噬作用与抗原呈递
Exam question: ‘Describe the process of phagocytosis by a macrophage. (4 marks)’
真题：”描述巨噬细胞的吞噬过程。（4分）”
Model answer: The macrophage detects the pathogen via chemotaxis and moves towards it. It recognises non-self antigens on the pathogen’s surface. The cell membrane invaginates and engulfes the pathogen, forming a phagosome. Lysosomes fuse with the phagosome to form a phagolysosome, where hydrolytic enzymes digest the pathogen. The macrophage then presents the pathogen’s antigens on MHC class II molecules on its surface, becoming an antigen-presenting cell (APC).
模型答案：巨噬细胞通过趋化作用探测到病原体并向其移动。它识别病原体表面的非我抗原。细胞膜内陷并将病原体包入，形成吞噬体。溶酶体与吞噬体融合形成吞噬溶酶体，其中的水解酶消化病原体。随后巨噬细胞通过其表面的 MHC II 类分子呈递病原体抗原，成为抗原呈递细胞 (APC)。
Examiner tip: Use sequential language (‘then’, ‘next’) to show chronological order. Mention specific structures: phagosome, lysosome, MHC II. Avoid vague terms like ‘eats’.
考官提示：使用顺序连接词以展现时间顺序。提及特定结构：吞噬体、溶酶体、MHC II。避免使用’吃掉’之类的模糊词汇。
5. Cell-Mediated Immunity | 细胞介导免疫
Exam question: ‘Describe the role of T lymphocytes in the immune response. (5 marks)’
真题：”描述 T 淋巴细胞在免疫应答中的作用。（5分）”
Model answer: Specific T helper cells have receptors that bind complementary antigens presented by APCs. Once activated, T helper cells divide to produce clones. They release cytokines (interleukins) that stimulate B cells to divide and differentiate, activate cytotoxic T cells, and stimulate macrophages to perform more phagocytosis. Cytotoxic T cells recognise infected body cells displaying viral antigens on MHC I molecules and release perforin, causing cell lysis. Memory T cells remain for long-term immunity.
模型答案：特异性辅助 T 细胞具有能与 APC 呈递的互补抗原结合的受体。被激活后，辅助 T 细胞分裂产生克隆。它们释放细胞因子（白介素）刺激 B 细胞分裂和分化、激活细胞毒性 T 细胞并刺激巨噬细胞加强吞噬。细胞毒性 T 细胞识别在 MHC I 分子上显示病毒抗原的感染细胞，并释放穿孔素导致细胞裂解。记忆 T 细胞留存，提供长期免疫。
Examiner tip: Link T cell activation to antigen presentation. Clearly distinguish between helper and cytotoxic functions, and always mention cytokines as signalling molecules.
考官提示：将 T 细胞激活与抗原呈递联系起来。清楚区分辅助功能和细胞毒性功能，并务必提及作为信号分子的细胞因子。
6. Humoral Immunity | 体液免疫
Exam question: ‘Explain how B lymphocytes are activated and how they contribute to defence. (5 marks)’
真题：”解释 B 淋巴细胞如何被激活以及它们如何参与防御。（5分）”
Model answer: B cells have membrane-bound antibodies that act as receptors for a specific antigen. When the antigen binds, the B cell endocytoses the complex and presents peptides on MHC II. An activated T helper cell with a complementary receptor binds and releases cytokines, stimulating the B cell to undergo clonal expansion. Some daughter cells become plasma cells that secrete large quantities of soluble antibodies into the blood; these antibodies agglutinate pathogens, neutralise toxins, and mark them for phagocytosis. Others become memory B cells for rapid secondary response.
模型答案：B 细胞表面有膜结合抗体，可作为特异性抗原的受体。当抗原结合后，B 细胞通过内吞作用处理复合物并在 MHC II 分子上呈递肽段。具有互补受体的活化辅助 T 细胞与其结合并释放细胞因子，刺激 B 细胞进行克隆扩增。部分子细胞成为浆细胞，向血液大量分泌可溶性抗体；这些抗体使病原体凝集、中和毒素并标记它们以让吞噬细胞吞噬。另一些成为记忆 B 细胞，以便在二次应答时快速反应。
Examiner tip: Don’t confuse humoral and cell-mediated pathways. Emphasise the role of T helper cells in B cell activation, and state the functions of antibodies explicitly.
考官提示：不要混淆体液免疫和细胞介导途径。强调辅助 T 细胞在 B 细胞激活中的作用，并明确列出抗体的功能。
7. Vaccination and Herd Immunity | 疫苗接种与群体免疫
Exam question: ‘Explain how vaccination can protect an individual and a population from a communicable disease. Use the term herd immunity in your answer. (4 marks)’
真题：”解释疫苗接种如何保护个体和人群免受传染性疾病侵害。请在答案中使用’群体免疫’一词。（4分）”
Model answer: Vaccination introduces a weakened or inactive form of the pathogen, or its antigens, which triggers a primary immune response. This produces memory B and T cells specific to the pathogen. Upon later exposure to the real pathogen, the secondary immune response is rapid and strong, preventing illness. At the population level, when a high percentage of individuals is vaccinated, herd immunity is achieved – the chain of transmission is interrupted, so even unvaccinated individuals gain indirect protection because the pathogen cannot circulate easily.
模型答案：疫苗接种导入弱化或灭活的病原体或其抗原，从而引发初次免疫应答。这会产生针对该病原体的记忆 B 细胞和 T 细胞。当后来接触真正的病原体时，二次免疫应答迅速而强烈，从而预防疾病。在人群层面，当接种率达到很高比例时，就实现了群体免疫——传播链被打断，因此即使未接种疫苗的个体也因病原体不易传播而获得间接保护。
Examiner tip: Always refer to ‘memory cells’ when explaining long-term protection. For herd immunity, explicitly mention interruption of transmission and protection of vulnerable individuals.
考官提示：解释长期保护时务必提及’记忆细胞’。对于群体免疫，要明确指出传播的中断和对弱势个体的保护。
8. Antibiotics and Antibiotic Resistance | 抗生素与抗药性
Exam question: ‘Explain why antibiotics are ineffective against viral infections. Describe the process by which bacteria become resistant to an antibiotic. (5 marks)’
真题：”解释为何抗生素对病毒感染无效。描述细菌对抗生素产生抗药性的过程。（5分）”
Model answer: Antibiotics target structures and metabolic processes specific to bacteria, such as cell wall synthesis (e.g., penicillin), protein synthesis (70S ribosomes) or DNA replication enzymes. Viruses lack these targets; they use host cell machinery to replicate, so antibiotics cannot harm them. Resistance develops through natural selection: within a bacterial population, a few individuals may carry a mutation that confers resistance. When the antibiotic is used, most bacteria die, but resistant ones survive and reproduce, passing the resistance allele to their offspring. This gene can also spread via horizontal gene transfer (conjugation). Over time, the population becomes dominated by resistant strains.
模型答案：抗生素靶向细菌特有的结构和代谢过程，如细胞壁合成（如青霉素）、蛋白质合成（70S 核糖体）或 DNA 复制酶。病毒缺乏这些靶点；它们利用宿主细胞机器复制，因此抗生素无法伤害它们。抗药性通过自然选择产生：在细菌种群中，极少数个体可能带有抗药性突变。当使用抗生素时，大多数细菌死亡，但抗药菌存活并繁殖，将抗性等位基因传给后代。该基因还可通过水平基因转移（接合）传播。随时间推移，种群逐渐以抗药菌株为主。
Examiner tip: Include the genetic basis (mutation) and the selection mechanism. For high marks, mention horizontal gene transfer and provide an example of an antibiotic’s specific target.
考官提示：要包含遗传基础（突变）和选择机制。为得高分，需提及水平基因转移并举例说明抗生素的具体靶点。
9. Preventive Measures and Public Health | 预防措施与公共卫生
Exam question: ‘Evaluate the effectiveness of quarantine and improved sanitation in controlling the spread of a waterborne disease like cholera. (5 marks)’
真题：”评估隔离检疫和改善卫生设施在控制像霍乱这样的水源性疾病传播方面的有效性。（5分）”
Model answer: Quarantine isolates symptomatic and asymptomatic carriers, directly preventing them from contaminating water sources and infecting others through direct contact. It is highly effective in an outbreak but can be difficult to enforce and may infringe on personal freedom. Improved sanitation, such as providing clean drinking water and constructing proper sewage systems, tackles the root cause of waterborne diseases. It offers long-term, sustainable protection and benefits the entire community. However, infrastructure is expensive and requires time to implement. Combining both measures provides immediate containment while addressing the underlying source of infection.
模型答案：隔离检疫能够隔开有症状和无症状携带者，直接防止他们污染水源和通过直接接触感染他人。它在疫情暴发时非常有效，但执行困难，并可能侵犯个人自由。改善卫生设施，如提供洁净饮水和修建完善的排污系统，能解决水源性疾病的根本原因，提供长期可持续的保护并惠及整个社区。然而，基础设施成本高昂且需要时间落实。两者结合能立即控制疫情，同时解决根本的感染来源。
Examiner tip: For ‘evaluate’ questions, give both strengths and limitations. Use connectives like ‘however’ and ‘whereas’, and always link the preventive measure to the specific mode of transmission.
考官提示：在’评估’类题目中，要给出优点和局限。使用’然而’、’而’等连接词，并始终将预防措施与具体的传播方式相联系。
10. Data Interpretation in Epidemiology | 流行病学中的数据解读
Exam question: ‘The graph shows the number of reported cases of measles in a country before and after the introduction of a national vaccination programme in 2000. Describe and explain the trend shown. (4 marks)’
真题：”图表显示了一个国家在 2000 年引入全国疫苗接种计划前后麻疹报告病例的数量。描述并解释所呈现的趋势。（4分）”
Model answer: Before 2000, the number of cases was high and fluctuated between seasons, with regular peaks. After the vaccine programme began, cases dropped dramatically and remained consistently low. The sharp decline occurred because vaccination induced artificial active immunity in a large proportion of the population, producing memory cells and antibodies specific to the measles virus. This reduced the number of susceptible hosts and, when coverage exceeded approximately 90–95%, herd immunity was established, effectively breaking the chain of transmission. Data manipulation tip: always quote key time points and describe the overall shape of the curve before explaining the biological reason.
模型答案：在 2000 年之前，病例数量很高且随季节波动，出现规律性高峰。疫苗接种计划启动后，病例数剧降并持续保持低水平。急剧下降是因为疫苗接种为大部分人群诱导了人工主动免疫，产生了针对麻疹病毒的记忆细胞和抗体。这减少了易感宿主的数量，当接种覆盖率超过约 90–95% 时便建立了群体免疫，有效阻断了传播链。数据处理技巧：始终引用关键时间点并描述曲线总体形态，然后再解释生物学原因。
Examiner tip: Be specific – use data (e.g., ‘dropped from approximately 50,000 cases in 1999 to under 1,000 by 2005’) and explicitly link the trend to immunological concepts such as herd immunity and secondary response failure.
考官提示：具体化——使用数据（如”从 1999 年的约 5 万例降至 2005 年的不足 1 千例”）并明确将趋势与群体免疫等免疫学概念相联系。
Published by TutorHao | Biology Revision Series | aleveler.com
更多咨询请联系16621398022（同微信）
屏轩国际教育cambridge primary/secondary checkpoint, cat4, ukiset,ukcat,igcse,alevel,PAT,STEP,MAT, ibdp,ap,ssat,sat,sat2课程辅导，国外大学本科硕士研究生博士课程论文辅导