This free quiz has 12 real AQA A-level Biology exam questions on the immune system (27 marks, about 35 minutes). It marks itself: for each answer you check your work against the real AQA mark scheme and tick the points you made.
What the quiz covers (AQA 3.2.4)
what a monoclonal antibody is, and the role of antibodies in the ELISA test (4 marks)
the structure of HIV, and why there is no effective HIV vaccine
how HIV affects antibody production when AIDS develops
how a phagocyte destroys a pathogen
which cells can stimulate an immune response
the role of helper T cells, and how a vaccine leads to antibody production (4 marks)
how antibodies stimulate phagocytosis, and how antivenom gives passive immunity
using antibody data to compare two and three doses of a vaccine
How to use it
Write each answer in full before you open the mark scheme, then tick only the points you really made. Use precise terms such as phagosome, lysosome, plasma cell and memory cell, and say an antibody's binding site is complementary to the antigen. For the vaccine graph, compare the two schedules directly rather than describing each one.
Where students lose marks (from AQA examiners’ reports and mark schemes)
Each point below is followed by wording that gained marks.
Binding sites, not active sites. Many students wrote about an antibody's “active site”, or about enzyme–substrate complexes, when describing how antibodies bind. Others wrote that an antibody is complementary without saying that it binds.
✔ Gains credit: the antigen-binding site of an antibody is complementary to a specific antigen, so it binds to form an antigen–antibody complex.
Bind, then destroy. Many students described antibodies binding to a toxin without saying it is then destroyed, or treated antivenom as a vaccine that triggers an immune response. “Clotting” and “killing” the toxin were not credited.
✔ Gains credit: antibodies bind to the toxin (antigen) and cause its destruction, for example by agglutination or phagocytosis.
Vesicles and lysosomes. Some students wrote about vacuoles rather than vesicles, or confused lysosomes (organelles) with lysozymes (enzymes).
✔ Gains credit: the phagocyte engulfs the pathogen, forming a phagosome (vesicle) that fuses with a lysosome, and lysozymes then hydrolyse the pathogen.
Specific B cells and plasma cells. Few students said the B cell is specific to the antigen, and some confused T cells and B cells over which make antibodies. Others wrote that B cells are “activated” without saying what they then do, or didn't name plasma cells.
✔ Gains credit: a specific B cell divides by mitosis to form a clone of plasma cells, which produce antibodies, and memory cells.
Memory cells and boosters. Answers about repeat vaccinations often said the response was “stronger” or “faster” without mentioning memory cells or antibodies. Many wrote “high” or “fast” antibody production instead of making a comparison.
✔ Gains credit: more memory cells are made, so on further exposure antibodies are produced more rapidly and in a higher concentration.
How HIV replicates. Only 1.89% of students gave a full description of HIV replication. Many used vague phrases such as “new viruses are made using the cell's own machinery”.
✔ Gains credit: reverse transcriptase converts HIV RNA into DNA, which is inserted into the helper T cell's DNA, then transcribed into mRNA and translated into new viral proteins.
ELISA needs an enzyme. Some answers had antigen–antibody complexes reacting with a substrate, or mentioned only a coloured dye, without involving an enzyme. The colour change only gains credit if the enzyme is mentioned.
✔ Gains credit: a second antibody with an enzyme attached binds, and the enzyme converts the substrate into a coloured product.
Keep practising
The other AQA 3.2 self-marking quizzes: Cell structure · Mitosis · Membrane transport
Topic 3.1 quizzes start with carbohydrates
The AQA topic index
weekly AQA group classes: Year 12 on Tuesdays at 5.15pm, Year 13 on Wednesdays or Thursdays at 6.30pm
Questions © AQA, from past A-level and AS Biology papers, with their mark schemes and examiners’ reports.