DP Chemistry (last assessment 2024)
Question 20N.3.hl.TZ0.c(i)
| Date | November 2020 | Marks available | [Maximum mark: 2] | Reference code | 20N.3.hl.TZ0.c(i) |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Label, Sketch | Question number | c(i) | Adapted from | N/A |
c(i).
[Maximum mark: 2]
20N.3.hl.TZ0.c(i)
Proteins are polymers of amino acids.
Sketch and label two oxygen dissociation curves, one for adult hemoglobin and one for foetal hemoglobin.
[2]
Markscheme
both curves sigmoidal shape AND starting at zero ✔
foetal hemoglobin showing greater affinity/steeper/higher gradient ✔
Do not penalize if convergence is not approached for M1.
Both curves must be labelled to score M2.
Examiners report
The better candidates scored both marks in this question on oxygen dissociation curves. Many scored M2 for showing foetal hemoglobin having a higher gradient. Frequently sigmoidal curves were not drawn which lost M1 and often both curves were not explicitly labelled which was necessary to score M2.