(a(i))[2]
The change in colour of apple tissue happens because of a sequence of chemical reactions. An enzyme called PPO catalyses one of these reactions. State what is meant by the term catalyst.
(a(ii))[4]
The colour change can be stopped by putting the cut surface of the apple tissue into boiling water for a short time straight after the fruit is cut. Explain this observation using the lock and key hypothesis of enzyme action.
(b)[3]
Scientists have recently used genetic engineering to create a kind of apple that does not make the enzyme PPO in its tissues. Suggest possible advantages of this kind of apple.