Question 22N.1A.HL.TZ0.31
| Date | November 2022 | Marks available | [Maximum mark: 1] | Reference code | 22N.1A.HL.TZ0.31 |
| Level | HL | Paper | 1A | Time zone | TZ0 |
| Command term | Question number | 31 | Adapted from | N/A |
What occurs in the light-independent reactions of photosynthesis?
A. Glycerate 3-phosphate is reduced to triose phosphate.
B. Ribulose bisphosphate is regenerated using reduced NADP.
C. Ribulose bisphosphate is oxidized to two molecules of glycerate 3-phosphate.
D. Both ATP and NADP are used to produce triose phosphate.
[1]
A
Both questions 31 and 32 were answered correctly by fewer than 40% of candidates. In question 31 this either indicates poor understanding of the Calvin cycle or careless reading of the possible answers, in which each word matters. In question 32 the poor performance suggests unfamiliarity with the use of potometers - a prescribed practical for Higher Level students. Many candidates thought that the volume of water in the reservoir had to be controlled, when in fact the reservoir is used to control the position of the air bubble in the capillary tube at the start of each measurement period.
The discrimination index in question 31 was high suggesting that the better-prepared candidates answered it correctly, but in question 32 it was relatively low. This suggests that much of the variance was between schools rather than between candidates, emphasizing the need for all prescribed practicals to be included in the teaching program.
