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IGCSEBiology
Trial Class

Original practice · 5 questions · 16 marks · about 18 minutes

Immune Response Practice Questions

Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.

These questions test your understanding of how the body defends itself against pathogens using physical barriers and the immune system.

Before you open the answers

  • Attempt every question without notes.
  • Show working for calculations and write complete biological statements.
  • Use the suggested time as a guide, not a strict limit on the first attempt.

These are original practice questions. They do not reproduce an official Cambridge paper or official mark scheme.

  1. Question 1

    Paper 4 Both 4 marks Difficulty 3/5

    Describe three physical or chemical barriers that prevent pathogens from entering the body.

    Show model answer and marking guidance
    1. Skin: acts as a physical barrier; outer layer of dead cells is difficult for pathogens to penetrate.
    2. Mucus in the airways: traps pathogens; cilia sweep mucus to the throat.
    3. Hydrochloric acid in the stomach: kills bacteria in food.
    4. Tears/saliva contain lysozyme: an enzyme that destroys bacterial cell walls.

  2. Question 2

    Paper 4 Extended 4 marks Difficulty 4/5

    Describe how lymphocytes respond to a pathogen that enters the body.

    Show model answer and marking guidance
    1. Lymphocytes recognise specific antigens on the surface of the pathogen.
    2. They produce antibodies that are complementary to / specific to the antigens.
    3. Antibodies bind to antigens, causing agglutination / clumping or marking pathogens for destruction.
    4. Memory cells are produced: these allow a faster response if the same pathogen enters again.

  3. Question 3

    Paper 4 Both 3 marks Difficulty 3/5

    Describe how phagocytes destroy pathogens.

    Show model answer and marking guidance
    1. Phagocytes are attracted to the site of infection.
    2. They engulf the pathogen by surrounding it with their cell membrane (phagocytosis).
    3. The pathogen is enclosed in a vacuole and digested by enzymes.

  4. Question 4

    Paper 2 Core 2 marks Difficulty 1/5

    Define the term "antigen".

    Show model answer and marking guidance
    1. A molecule / protein on the surface of a cell or pathogen.
    2. That triggers an immune response / is recognised as foreign by the immune system.

  5. Question 5

    Paper 4 Extended 3 marks Difficulty 4/5

    Explain the difference between the primary immune response and the secondary immune response.

    Show model answer and marking guidance
    1. Primary response is slow: lymphocytes must first recognise the antigen and multiply before producing antibodies.
    2. Secondary response is faster and stronger: memory cells from the first infection are already present.
    3. Memory cells rapidly divide and produce large quantities of specific antibodies.

Mark the set consistently

Award a point only when the idea is clearly present in the written answer. Correct any missed point in a complete sentence, then test the same skill on a different question several days later.

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