Chemguide: Support for CIE A level Chemistry


Learning outcome 8.3(d)

This statement is a brief introduction to enzymes as catalysts.

Before you go on, you should find and read the statement in your copy of the syllabus.


Unless you have already come across enzymes in biology or biochemistry, don't get too bogged down in this at this stage. In fact, unless you have already done the chemistry of amino acids and proteins, it is hard to explain much about enzymes apart from in very general terms.

Essentially, all you need to know for now is that:

  • Enzymes are biological catalysts.

  • Enzymes are protein molecules. Possibly the most likely thing to be asked in an exam in the first year of the course is simply "What type of substance is an enzyme?". Answer: a protein.

  • Enzymes operate via a "lock and key" mechanism. (See the link below.)

  • Because of this, enzymes are usually very specific. An enzyme that will catalyse one reaction probably won't catalyse another reaction.

You will find this (and a lot more) on the page about proteins as enzymes.

You should only read down as far as the paragraph under the first diagram in the Active Sites section. You don't need to go beyond that. And don't waste time looking at the page about the structure of proteins. You will come back to proteins in the second half of the course in Section 21.


Go to the Section 8 Menu . . .

To return to the list of learning outcomes in Section 8

Go to the CIE Main Menu . . .

To return to the list of all the CIE sections

Go to Chemguide Main Menu . . .

This will take you to the main part of Chemguide.


© Jim Clark 2011 (last modified April 2014)