Unit 2 - Enzymes

Enzymes are proteins and their molecules act as biological catalysts. This means that they speed up chemical reactions in living organisms, and in this GCSE Biology quiz we are going to take a closer look at some of the different enzymes, what they do and how they work.

Enzymes function because they are long molecules that are twisted and folded into a specific and usually very complex shape. The shape allows smaller chemicals (substrate molecules) to fit into certain places called active sites. This brings the substrate chemicals close together and so they can react more easily than they would do otherwise.

Enzymes work best at specific temperatures and pH levels, for example, human enzymes work best at about 37^oC. They are sensitive to temperature and pH, and change their shape under conditions of moderately high temperatures (45^oC and above) and values of pH that differ from the ones in which they normally work. When they change shape like this, we say that they are denatured and the active sites will no longer work as efficiently. As the temperature or pH becomes more extreme, the active sites stop working altogether.