Chemguide: Support for CIE A level Chemistry

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 heading "Enzyme cofactors". You don't need to go beyond that heading at the moment. Don't worry too much for now if there are things in what you have read which you don't fully understand. You will come back to this in detail later in the course in the Applications section of the syllabus (section 11.1) - sort it out then.

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