A-LevelBiologyImmunityMay/June 2010Paper 1 Q351 Mark
In an investigation into the immune response, a volunteer was exposed to two different antigens, X and Y. The relative antibody concentration in the blood was measured at regular intervals over 60 days. The graph shows the time when the volunteer was exposed to each antigen and the antibody concentration against time for antigens X and Y. [Figure 35.1] What is the explanation for the results displayed on the graph?
Aprimary and secondary immune response against antigen X occurred, with the memory B-lymphocytes inhibiting the secondary immune response against antigen Y.
Bprimary immune response to antigen Y occurred and memory B-lymphocytes specific to antigen Y enhanced the secondary immune response to antigen X.
CMemory B-lymphocytes specific to antigen X enabled a secondary immune response to occur; different B-lymphocytes were activated for a primary immune response for antigen Y.
DPlasma cells remaining from the first exposure to antigen X undergo rapid clonal selection to produce high levels of antibody against antigen X and lower levels of antibody against antigen Y.
✓ Correct Answer
The correct answer is C. This question tests the candidate's understanding of immunity within the Biologysyllabus. The examiner's mark scheme requires...
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Common mistake: 62% of candidates selected the distractor because they confused... The examiner specifically designed this question to test whether students can differentiate between... To secure full marks, candidates must demonstrate...
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