Infectious Disease: Biology 9700 (Cambridge International AS & A Level)
Syllabus 10.1, 10.2 · Strand 4 Health, disease and immunity
- Questions
- 10
- Total marks
- 56
- Tier mix
- 10 Core
0 of 10 questions completed
Syllabus coverage
- 10.1 7 questions completed
- 10.2 5 questions completed
Infectious diseases are caused by pathogens that pass from one host to another, and this topic (syllabus 10.1 and 10.2) looks at four major examples and at the drugs used against them. For cholera, malaria, tuberculosis and HIV/AIDS you should know the name and type of pathogen responsible, from the bacterium Vibrio cholerae to the Plasmodium protoctists, the Mycobacterium species and the human immunodeficiency virus. Understanding how each disease is transmitted, whether through contaminated water, an insect vector, airborne droplets or body fluids, is the key to explaining how it can be controlled. You are also expected to discuss the biological, social and economic factors that make prevention easier or harder in different parts of the world.
The topic then turns to antibiotics. Penicillin works by disrupting the formation of bacterial cell walls, which is why it kills bacteria but has no effect on viruses, whose replication uses the host’s own machinery. A major theme is antibiotic resistance: its rise as a consequence of natural selection when antibiotics are overused or misused, the serious consequences of infections that no longer respond to treatment, and the steps that individuals, doctors and governments can take to slow it down.
The exam-style questions below are original, written to match these objectives, each with a full worked solution so you can check your reasoning step by step.
Question 1
Cholera, malaria, tuberculosis and HIV/AIDS are all infectious diseases, but each is caused by a different type of pathogen.
Which option correctly identifies the type of organism that causes each of these four diseases?
Question 2
Cholera is a disease of the small intestine.
(a) State the type of pathogen that causes cholera and describe how the toxin it produces leads to the symptoms of the disease. [3]
(b) Explain how cholera is usually transmitted from one infected person to another. [2]
(c) After a period of heavy flooding, the sewage system in the district of Meridale is badly damaged and sewage mixes with the local drinking-water supply. A large outbreak of cholera follows, and health workers find it difficult to bring under control. Using biological, social and economic factors, explain why this outbreak occurred and why it is difficult to control. [4]
Question 3
Malaria remains one of the world's most significant infectious diseases.
(a) State the type of organism that causes malaria in humans and describe how the pathogen is transmitted from one person to another. [3]
(b) Describe the role of the Anopheles mosquito in the transmission of malaria, and outline two ways in which controlling this mosquito can help to control the spread of the disease. [3]
(c) A rural region has high rainfall throughout the year, widespread poverty, and only one health clinic serving a large population. Using biological, social and economic factors, explain why malaria is difficult to control in this region. [3]
Question 4
Tuberculosis (TB) is an infectious disease that mainly affects the lungs.
(a) State the name and type of pathogen that usually causes tuberculosis, and explain how it is transmitted from one person to another. [3]
(b) Explain why tuberculosis spreads particularly easily among people living in overcrowded housing with poor ventilation. [2]
(c) A patient with tuberculosis is treated with an antibiotic that prevents bacteria from cross-linking peptidoglycan in their cell walls. Explain how this antibiotic kills the bacterium that causes tuberculosis, and explain why the same antibiotic has no effect on a person suffering from measles, a viral disease. [4]
Question 5
For several years, doctors in a hospital ward used the same antibiotic to treat patients infected with Staphylococcus aureus. Initially, almost all Staphylococcus aureus bacteria in the ward were killed by this antibiotic. After several years of frequent use, most Staphylococcus aureus isolated from patients in the ward were resistant to it, a strain known as MRSA (methicillin-resistant Staphylococcus aureus).
Which statement correctly explains how this increase in antibiotic resistance came about?
Question 6
Penicillin is an antibiotic used to treat many bacterial infections.
Which statement correctly describes how penicillin kills susceptible bacteria?
Question 7
HIV/AIDS remains a major infectious disease in many parts of the world.
(a) State the type of pathogen that causes HIV/AIDS and describe two ways in which it can be transmitted from one person to another. [3]
(b) Describe two measures that can be used to reduce the transmission of HIV within a population. [3]
(c) A city has a large number of people living with HIV, but strong social stigma around the disease discourages many people from being tested, and public health budgets are limited. Explain how these social and economic factors make it more difficult to control the spread of HIV/AIDS in this city. [3]
Question 8
Cholera, malaria, tuberculosis and HIV/AIDS are each usually transmitted in a different way.
Which option correctly matches each disease to its main route of transmission?
Question 9
Antibiotic resistance has become more widespread among many bacterial species over the last few decades.
(a) Explain two reasons why the proportion of bacteria that are resistant to antibiotics has increased over this time. [4]
(b) Explain how a patient not completing a full course of antibiotics can contribute to the spread of antibiotic resistance within a hospital ward. [2]
(c) State two consequences for patients or health services when an infection is caused by antibiotic-resistant bacteria. [3]
Question 10
Tuberculosis (TB) is treated with a long course of antibiotics, usually lasting several months.
(a) Describe two measures, other than giving antibiotics to an infected patient, that can be used to control the spread of tuberculosis within a community. [3]
(b) A patient begins to feel better after a few weeks of antibiotic treatment for tuberculosis and stops taking the medication early. Explain why health workers advise patients to complete the full course of antibiotics, and outline one possible consequence if a patient does not. [4]