| Date | May 2017 | Marks available | 2 | Reference code | 17M.3.hl.TZ2.14 |
| Level | HL | Paper | 3 | Time zone | TZ2 |
| Command term | Explain | Question number | 14 | Adapted from | N/A |
Question
A hemoglobin-oxygen saturation curve does not follow the same model as enzyme-substrate reactions.
Explain the shape of the curve from 0 to X kPa.
[2]
a.
Explain why carbon monoxide is toxic to humans.
[2]
b.
Markscheme
oxygen binds to first active site «of deoxygenated heme» AND alters shape of other active sites
OR
cooperative binding
affinity of partially oxygenated hemoglobin for oxygen increases
[2 marks]
a.
CO is a competitive inhibitor «of oxygen binding to hemoglobin»
OR
CO has greater affinity for hemoglobin «than oxygen»
less oxygen is transported
OR
uptake of oxygen decreases
OR
causes hypoxia
Do not penalize “CO binds irreversibly” if included in answer.
[2 marks]
b.
Examiners report
[N/A]
a.
[N/A]
b.
