Biology Exams 2009

An Enzyme is a Biological Catalyst which speeds up the rate of reactions.
Enzymes are involved in:

• building large molecules from lots of smaller ones
• changing one molecule into another
• breaking down large molecules into smaller ones

Catalysts are not used up in the reaction so you can use them over and over again. They work by bringing reacting particles together and lowering the activation energy needed for them to react.

Enzymes are made up of large protein (amino acids) molecules which are folded and coiled into a very specific and unique shape. We call this the Active Site.

The Substrate of the reaction is the one which fits into the shape of the enzyme, like a "Lock and Key."

Once the enzyme and substrate bind together, we call this the enzyme substrate complex.