| Date | May 2011 | Marks available | 3 | Reference code | 11M.3.hl.TZ1.B4 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Determine | Question number | B4 | Adapted from | N/A |
Question
The kinetics of an enzyme-catalysed reaction are studied in the absence and presence of an inhibitor. The graph represents the initial rate as a function of substrate concentration.
Identify the type of inhibition shown in the graph.
Determine \({V_{\max }}\) and \({K_{\text{m}}}\) in the absence of the inhibitor and in the presence of the inhibitor.
Absence of inhibitor:
Presence of inhibitor:
Outline the relationship between \({K_{\text{m}}}\) and enzyme activity.
Markscheme
non-competitive (inhibition);
Absence of inhibitor:
\({V_{\max }}{\text{ }}4.4\)
\({K_{\text{m}}}{\text{ }}1.7\)
Accept 1.6–1.8.
Presence of inhibitor:
\({V_{\max }}{\text{ }}3.0\)
\({K_{\text{m}}}{\text{ }}1.7\)
Accept 1.6–1.8.
4 values correct, award [3]
3 values correct, award [2]
2 values correct, award [1]
1 value correct, award [0]
Ignore units.
higher the value of ({K_{\text{m}}}\), lower the activity of enzyme / lower the value of \({K_{\text{m}}}\), higher the activity of enzyme / OWTTE;
Examiners report
This part was generally well answered with full marks awarded to more than half of the candidates. Those who did not score full marks usually failed to give a correct answer in (a) and (c).
This part was generally well answered with full marks awarded to more than half of the candidates. Those who did not score full marks usually failed to give a correct answer in (a) and (c).
This part was generally well answered with full marks awarded to more than half of the candidates. Those who did not score full marks usually failed to give a correct answer in (a) and (c).
