| Date | May 2011 | Marks available | 2 | Reference code | 11M.3.HL.TZ1.14 |
| Level | Higher level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Draw | Question number | 14 | Adapted from | N/A |
Question
The oxygen dissociation curve is a graph that shows the percentage saturation of hemoglobin at various partial pressures of oxygen. Curve A shows the dissociation at a pH of 7 and curve B shows the dissociation at a different pH.
Outline how coronary thrombosis can be caused.
State the possible cause of the curve shifting from A to B.
On the graph, draw the curve for myoglobin.
Describe the breakdown of hemoglobin in the liver.
Markscheme
atheroma/fatty deposits in arteries;
hardening of arteries/atherosclerosis/arteriosclerosis;
rough surface causes rupture of platelets;
clots form in coronary artery;
increase in CO2 concentration;
decrease in pH;
graph drawn to left of A;
curve not sigmoid;
As shown below.
hemoglobin absorbed by phagocytes/Kupffer cells;
split into heme and globins;
globin hydrolysed/broken down to amino acids;
iron removed from heme group / heme broken down to form bilirubin/bile pigment;
Examiners report
The outline of how coronary thrombosis can be caused was surprisingly poorly done. Most simply gave a list of risk factors without actually stating what caused the thrombosis.
This section on the oxygen dissociation curve was also poorly done. Few stated that the shift in the curve could be due to either an increase in CO2 concentration or a decrease in pH.
N/A
The full two marks for this section were often awarded as candidates seemed to know where and into what hemoglobin was broken down.
