Question 18N.3.hl.TZ0.11
| Date | November 2018 | Marks available | [Maximum mark: 4] | Reference code | 18N.3.hl.TZ0.11 |
| Level | hl | Paper | 3 | Time zone | TZ0 |
| Command term | Explain | Question number | 11 | Adapted from | N/A |
The transport of oxygen around the body is essential for life.
A graph showing saturation of oxygen against partial pressure of oxygen is shown.
Explain the shape of the graph from 0 to 50 % saturation.
[2]
binding of oxygen/O2 «to one active site» affects shape of Hb/other active sites
OR
binding of one oxygen/O2 «molecule» affects binding of other oxygen/O2 «molecules» ✔
increasing affinity of Hb to oxygen/O2
OR
enhanced binding of «further» oxygen/O2 «molecules»
OR
cooperative binding ✔
Explain why carbon monoxide is very toxic and how it may be possible to treat carbon monoxide poisoning.
[2]
Toxicity:
carboxyhemoglobin/Hb–CO does not readily dissociate
OR
CO + Hb Hb–CO AND forward reaction favoured
OR
affinity of carbon monoxide/CO for hemoglobin is «200 times/much» higher than that of oxygen/O2
OR
competitive inhibitor of oxygen/O2 binding ✔
Treatment:
moving patient to fresh air
OR
«in severe cases» inhaling pure oxygen/O2
OR
high pressure oxygen/O2 chamber ✔
Accept “move away from carbon monoxide/CO source” OR “remove carbon monoxide/CO source”.