48 exam-style questions on Defence against disease — topic C3.2 of Interaction and interdependence in the IB Biology syllabus — with answers and explanations. Samples below; the full set is free with an account.
During an immune response, antibodies are secreted by:
Answer: Plasma cells
Activated B lymphocytes proliferate and differentiate into plasma cells, which mass-produce antibodies specific to the antigen. Some become memory cells for faster future responses.
Vaccination produces long-term immunity mainly by stimulating the formation of:
Answer: Memory cells
A vaccine exposes the immune system to antigens, triggering a primary response and the production of memory cells. On later exposure to the real pathogen these enable a rapid, strong secondary response.
State the type of white blood cell that engulfs and digests pathogens by phagocytosis as part of the non-specific immune response.
Answer: Phagocyte
Phagocytes such as macrophages carry out phagocytosis, engulfing pathogens non-specifically; lymphocytes mediate the specific response and erythrocytes carry oxygen.
Explain how a specific antibody helps to defend against a particular pathogen.
Answer: Its variable region binds one antigen, marking the pathogen
The variable region of each antibody has a specific shape complementary to one antigen; binding neutralizes or agglutinates pathogens and marks them for phagocytosis.
A person recovers from an infection. On second exposure to the same pathogen the secondary immune response differs from the primary response because it:
Answer: Is faster and produces more antibodies due to memory cells
Memory cells formed during the primary response allow the secondary response to be faster and to produce a higher concentration of antibodies, often clearing the pathogen before symptoms appear.
Determine which molecule enables the clotting cascade to convert soluble fibrinogen into insoluble fibrin during blood clotting.
Answer: Thrombin
Thrombin, an enzyme produced during the clotting cascade, catalyses the conversion of soluble fibrinogen into insoluble fibrin, which forms the clot mesh.
That was 6 of 48 Defence against disease questions.
Practise all 48 freeStateAO1 · 1–2 marks
One word or one short sentence. No explanation, no working: the mark is for the fact itself.
OutlineAO2 · 1–4 marks
A brief account or summary: the main points in two or three sentences, no evaluation.
DescribeAO2 · 1–4 marks
Give a detailed account of what it is or how it happens — steps, features, pattern — without saying why.
48 Defence against disease questions — free with an account. Spaced repetition, streaks and full exam simulations included.
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