| Date | May 2012 | Marks available | 5 | Reference code | 12M.3.hl.TZ1.B1 |
| Level | HL | Paper | 3 | Time zone | TZ1 |
| Command term | Question number | B1 | Adapted from | N/A |
Question
A large proportion of the food we eat provides energy through the process of respiration. Carbohydrates and triglycerides are the food groups mainly responsible for providing this energy.
Compare the behaviour of enzymes and inorganic catalysts, including reference to the mechanism of enzyme action and the ways in which this can be inhibited.
Markscheme
Any three for first three marks:
both increase rate of chemical reactions;
both reduce activation energy;
both provide alternative pathways for reaction;
enzymes more specific;
enzymes have active site that substrate bonds to / “lock and key” mechanism;
enzymes much more readily denatured by changing conditions;
Both required for final two marks:
competitive inhibitors and non-competitive inhibitors;
competitive inhibitors bond to active site and non-competitive inhibitors denature/alter shape of enzyme;
Examiners report
The final section comparing enzymes and catalysts was generally well answered, though quite a few neglected to discuss the similarities of the two.
