Infection and response flashcards

Infection and response covers how pathogens cause disease and how the body defends itself. Students must understand the four types of pathogen: bacteria, viruses, fungi and protists, and be able to give examples of diseases caused by each. The body has non-specific defences such as skin, mucus and stomach acid, as well as a specific immune response involving white blood cells that produce antibodies. Students should understand how vaccines work, how medicines such as antibiotics and antivirals are used, and why antibiotic resistance is a growing problem. The discovery and development of drugs, including the work of Fleming, Florey and Chain, is also important. Students should be able to evaluate the stages of drug testing and understand why new medicines must pass through clinical trials before being approved for use.

1. Card 1

   What is a pathogen?

   A pathogen is a microorganism that causes infectious disease. Examples include bacteria, viruses, fungi and protists.

2. Card 2

   How do bacteria cause harm in the body?

   Bacteria damage the body by reproducing rapidly and releasing toxins, which are poisonous substances that interfere with normal body functions.

3. Card 3

   How do viruses cause harm in the body?

   Viruses invade body cells and use them to replicate. This causes the host cell to burst and be destroyed, releasing new virus particles.

4. Card 4

   Name one disease caused by a protist and explain how it spreads.

   Malaria is caused by a protist. It is spread by female Anopheles mosquitoes, which act as vectors, transferring the pathogen when they bite a human host.

5. Card 5

   What are three non-specific defences the body uses against pathogens?

   The skin acts as a physical barrier, mucus in the airways traps pathogens, and stomach acid kills pathogens that are swallowed.

6. Card 6

   What is the role of antibodies in the immune response?

   Antibodies are proteins produced by lymphocytes that bind to specific antigens on pathogens, marking them for destruction or neutralising them directly.

7. Card 7

   Why does the immune response work faster the second time you encounter a pathogen?

   Memory cells remain in the blood after the first infection. On re-exposure they rapidly produce large amounts of antibodies before symptoms can develop.

8. Card 8

   How do vaccines protect individuals and communities?

   Vaccines introduce a weakened or dead pathogen, triggering immunity without causing disease. Widespread vaccination creates herd immunity, protecting vulnerable people.

9. Card 9

   What is the difference between antibiotics and antivirals?

   Antibiotics kill or inhibit bacteria but have no effect on viruses. Antivirals are medicines specifically designed to treat viral infections.

10. Card 10

    Why is antibiotic resistance a serious concern?

    Overuse of antibiotics means bacteria evolve through natural selection, producing resistant strains that cannot be killed by existing antibiotics, making infections harder to treat.

11. Card 11

    What were the three main stages of drug testing before a medicine reaches patients?

    Drugs are tested in the laboratory on cells and tissues, then on animals, then in clinical trials on human volunteers to check safety, dosage and effectiveness.

12. Card 12

    What is a double-blind trial and why is it used?

    In a double-blind trial neither patients nor doctors know who receives the drug or a placebo, eliminating bias and ensuring results are reliable.

• Many students confuse antibiotics with antivirals and incorrectly state that antibiotics can be used to treat viral diseases such as colds or flu.
• Students often think that vaccination directly kills pathogens in the body, when in fact it works by stimulating the immune system to produce memory cells without causing the disease.
• A common error is to describe bacteria as always harmful, when in reality most bacteria are harmless or even beneficial, and only a small number are pathogens.

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