Home › Free Resources › Biology Worksheets › GCSE / IGCSE Biology – Infection and Response
Free Biology Worksheet

GCSE / IGCSE Biology – Infection and Response

Pathogens, immunity, vaccination, antibiotics.

WhatsApp Mr. AhmadBook a trial lesson (50% off)Free worksheets
12 questions  ·  39 marks  ·  answers included  ·  GCSE / IGCSE (Edexcel / Cambridge style)
Download the PDFAsk about a question

This worksheet covers:

  • This worksheet covers pathogens and disease
  • The body’s defences and immune response
  • Vaccination
  • Drug development including antibiotics

No calculator is needed.

Questions

Section A – Pathogens and Disease

Skills
1

Define “pathogen” and name the four types of pathogen studied in this topic, giving one example disease caused by each.

Show answer
A pathogen is a microorganism that causes infectious disease. Bacteria – e.g. Salmonella (food poisoning). Viruses – e.g. measles. Fungi – e.g. rose black spot (or athlete’s foot). Protists – e.g. malaria (caused by Plasmodium).
[5]
2

Describe two ways in which a disease-causing microorganism can be spread from one person to another.

Show answer
Any two of: direct contact (touching); through the air (droplet infection, e.g. coughing or sneezing); through contaminated water; via a vector (e.g. a mosquito); via bodily fluids.
[2]
3

Explain how the skin acts as a barrier to prevent the entry of pathogens into the body.

Show answer
The skin covers the body and provides a physical barrier that pathogens generally cannot penetrate; it also secretes antimicrobial substances (e.g. in sebum) that can inhibit the growth of microorganisms, and if it is cut, blood clots rapidly to seal the wound and prevent pathogens entering.
[2]

Section B – Immune Response and Vaccination

Exam-style
4

Describe how white blood cells defend the body against pathogens, referring to phagocytosis and antibody production.

Show answer
Some white blood cells (phagocytes) engulf and digest pathogens by phagocytosis. Other white blood cells (lymphocytes) produce antibodies that are specific to a particular antigen on the surface of a pathogen; the antibodies bind to these antigens, which helps to destroy the pathogen (e.g. by clumping pathogens together). Lymphocytes may also produce antitoxins that neutralise toxins produced by pathogens.
[4]
5

Explain how vaccination can protect an individual from a serious disease, referring to memory cells in your answer.

Show answer
A vaccine contains a small, safe (dead or inactive) form of a pathogen or its antigens. This stimulates white blood cells to produce antibodies specific to that pathogen, and the body also produces memory cells. If the person later encounters the live pathogen, the memory cells recognise the antigen and allow a much faster, stronger secondary immune response, destroying the pathogen before the person becomes ill.
[4]
6

A country introduces a vaccination programme against a viral disease. After several years, 92% of the population is vaccinated. Explain how this can protect even the unvaccinated 8% of the population.

Show answer
With such a high proportion of the population immune, the pathogen finds it much harder to spread between people (herd immunity), reducing the chance that an unvaccinated person comes into contact with someone carrying the disease. This protects the unvaccinated minority indirectly, even though they are not immune themselves.
[3]
7

Explain why antibiotics are not effective against viral infections such as the common cold.

Show answer
Antibiotics kill bacteria or inhibit their growth (e.g. by disrupting cell wall production), but viruses reproduce inside host cells using the host’s own cellular machinery, so they do not have the structures/processes that antibiotics target. Antibiotics therefore have no effect on viruses.
[2]

Section C – Drug Development and Extended / Challenge

8

Describe the main stages involved in the preclinical and clinical testing of a new medicinal drug, before it can be prescribed by doctors.

Show answer
Preclinical testing: the drug is tested on cells, tissues and live animals in the laboratory to check for toxicity, efficacy and the best dosage. Clinical testing: the drug is tested on healthy human volunteers at low doses to check for toxicity and side effects, then on patients in clinical trials to find the optimum dose; double-blind trials are often used, in which some patients receive a placebo and neither doctors nor patients know who received the drug until the trial is complete.
[4]
9

Explain why it is important to use a placebo and carry out a “double-blind” trial when testing a new drug.

Show answer
A placebo (containing no active drug) allows scientists to compare the effect of the real drug against a control, ruling out the placebo effect (patients feeling better simply because they believe they are being treated). In a double-blind trial, neither the patient nor the doctor knows who has the real drug or the placebo until the results are collected, which prevents bias affecting how patients report symptoms or how doctors interpret the results.
[3]
10

Bacteria can become resistant to antibiotics through natural selection. Explain how a population of bacteria in a patient could become resistant to a particular antibiotic over time.

Show answer
Within a large bacterial population, random mutation means a small number of bacteria may already carry (or develop) a gene giving resistance to the antibiotic. When the antibiotic is used, non-resistant bacteria are killed, but resistant bacteria survive and reproduce, passing the resistance gene(s) to their offspring. Over many generations, the proportion of resistant bacteria in the population increases, until eventually the whole population may become resistant.
[4]
11

Explain why it is important that doctors do not over-prescribe antibiotics, and that patients complete the full course of antibiotics prescribed.

Show answer
Overprescribing antibiotics (e.g. for viral illnesses, on which they have no effect) increases the rate at which bacteria are exposed to them, speeding up the development of resistant strains by natural selection. Completing the full course ensures nearly all of the bacteria, including less-susceptible ones, are killed, rather than stopping early and leaving surviving (potentially more resistant) bacteria to multiply and spread resistance.
[3]
12

Monoclonal antibodies are produced to be specific to one particular type of antigen. Suggest one use of monoclonal antibodies in medicine and briefly explain how they work in this use.

Show answer
Example: pregnancy testing. Monoclonal antibodies specific to the hormone hCG (present in the urine of pregnant women) are bound to a coloured dye on the test strip; if hCG is present in a urine sample, it binds to these antibodies, producing a colour change in the test window that indicates a positive result. (Other valid uses: diagnosing disease, or targeting drugs directly to specific cells such as cancer cells.)
[3]

Related worksheets

More worksheets in GCSE & IGCSE Biology:

GCSE / IGCSE Biology – Cell BiologyGCSE / IGCSE Biology – Organisation and PhysiologyGCSE / IGCSE Biology – BioenergeticsGCSE / IGCSE Biology – Inheritance and EvolutionGCSE / IGCSE Biology – Ecology

All biology worksheets  ·  Full resource library  ·  Biology tuition with Mr. Ahmad

Get new biology worksheets by email

One short email when new worksheets are added. No spam, unsubscribe any time.



    Book a trial lesson (50% off)

    Try a full first lesson with Mr. Ahmad at 50% off before you commit to anything. It is a real lesson, not a sales call: bring a topic the student is stuck on and we will work through it together.

    • Online from anywhere in the world, or in person across Dubai
    • You get honest feedback on where the student stands and what to fix first
    • No contract — if it is not the right fit, that is fine

    Prefer to talk? Message on WhatsApp and you will hear back within 24 hours.



      Stuck on this topic?

      Book a trial lesson with Mr. Ahmad at 50% off and bring this worksheet with you — online worldwide or in person in Dubai.

      WhatsApp nowBook a trial lesson (50% off)
      Scroll to Top