| Date | May 2010 | Marks available | 3 | Reference code | 10M.3.SL.TZ1.12 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 1 |
| Command term | Explain | Question number | 12 | Adapted from | N/A |
Question
Explain the control of metabolic pathways.
Markscheme
metabolic pathway is a series of reactions carried out in a particular sequence;
products of one reaction become substrates for the next;
each reaction is enzyme-catalyzed (and thus represents point of control);
some enzymes are allosteric;
allosteric control / end-product inhibition/negative feedback;
end-product acts as inhibitor of enzyme at beginning of pathway;
product binding changes the conformation of the active site so substrate of the pathway can no longer bind;
Examiners report
Only the better candidates understood what was required in this question and gained some marks. Many did not attempt an answer.
