What this practice covers
These questions are drawn from past CIE 9700 Biology papers and filtered to mode of action of enzymes. You answer, you find out immediately whether you were right, and you get the reasoning for the correct option and for each distractor. Wrong answers go to a mistakes locker so you can come back to exactly those.
Practice is free. You need an account only so your progress and your mistakes are still there next time.
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What examiners see students get wrong here
These are the errors that cost marks on mode of action of enzymes, taken from our own topic notes. Read them before you practise and you will recognise the traps in the questions.
- Saying the active site is "the same shape as" the substrate. It is complementary to it.
- Saying an enzyme "lowers the energy needed for the reaction". It lowers the activation energy, not the overall energy change.
- Saying denaturation "breaks the enzyme down" or "breaks the peptide bonds". Peptide bonds are unaffected; the bonds holding the tertiary structure break.
- Saying enzymes are used up. They are not, which is why a small quantity catalyses a large amount of reaction.
- Treating lock and key as simply wrong. It is an accurate description of specificity that induced fit refines.
Revise it first
If any of the above is unfamiliar, work through the notes before practising: Mode of action of enzymes revision notes.