CAIE A Level Biology 9700 · Immunity
The table shows the concentration of antibodies in the blood of a person following a first exposure to a novel antigen on day 0 and a second exposure to the same antigen on day 20.
| Time (days) | Antibody concentration (arbitrary units) |
|---|---|
| 0 | 0 |
| 5 | 10 |
| 10 | 100 |
| 15 | 80 |
| 20 | 60 |
| 22 | 200 |
| 25 | 500 |
| 30 | 400 |
Outline the sequence of events in the primary and secondary immune responses that account for the changes in antibody concentration shown in the table.
4 marks, so the mark scheme is looking for about 4 separate creditworthy points. Making the same point twice in different words earns it once.
Outline means: Give the main points briefly. Less detail than describe, but every key step has to be there. One short line per step, in order. The marks are for coverage, not depth.
Written by Markquill to follow the Cambridge International syllabus. Markquill is independent and is not affiliated with or endorsed by Cambridge International.