Question 21M.2.HL.TZ2.6b
| Date | May 2021 | Marks available | [Maximum mark: 7] | Reference code | 21M.2.HL.TZ2.6b |
| Level | HL | Paper | 2 | Time zone | TZ2 |
| Command term | Explain | Question number | b | Adapted from | N/A |
Explain the production of antibodies when a patient is infected with the TB bacterium.
[7]
a. phagocytes/lymphocytes are white blood cells ✔
b. TB bacterium has a specific antigen ✔
c. this antigen is recognised by white blood cells ✔
d. a clone of lymphocytes/plasma cells/B cells are produced ✔
e. antibodies are produced by lymphocytes ✔
f. each lymphocyte produces just one type of antibody ✔
g. (this is) specific immunity ✔
h. (part of the) antibody/immunoglobulin binds to the antigen / specific antibody binds to the specific antigen ✔
i. antibodies are proteins/immunoglobulins ✔
j. (some) plasma cells become memory cells ✔
k. memory cells reproduce quickly ✔
l. memory cells prevent infection in the future ✔
Allow annotated diagrams to explain the process.
(attempted by about 60 % of the cohort)
Part (a) was a departure from the 'draw a prokaryote' type of question that has appeared numerous times. In general, it was well answered. There were some good diagrams as answers which clearly showed only the prokaryotic characteristics. Part (b) asked for an explanation of the production of antibodies. Many weaker students wrote at length about non-specific phagocytosis which was not credited. Weaker students confused antibodies and antigens and even talked about antibiotics. This question was designed to be answered by the Standard Level students using Standard Level material. Some tried to include HL material and became very confused. Part (c) was really a question about Darwin's theory of evolution set in context. Many of the answers were very Lamarckian with the antibiotic causing the mutation, instead of some bacteria already having resistance. Better students opened with comments and an explanation that antibiotics only kill bacteria.
