See how different concentrations of yeast affects how much oxygen is given off in 1 minute, when 10cm3 of yeast (which contains catalyse) is mixed with 10cm3 of hydrogen peroxide.

Catalase is an enzyme found in all living cells. It makes Hydrogen Peroxide decompose into water and oxygen.

You can represent this in the equation:

2H2O2 =2H2O + O2

Enzymes: Enzymes are able to increase the rate of reaction without actually being consumed in the process. In all, enzymes are very efficient. Small quantities at low temperatures are able to produce results, which would require high temperatures and a violent reaction from any normal chemical means. Although increases in temperature may speed up the reaction, enzymes are unstable when heated.

There are three important definitions that are used when talking about enzymes: -

The substance that enzymes act on is the substrate.

The substance formed by the reaction is the product

The site on which the enzyme takes place is called the active site.

Enzyme function can be explained by the Lock and Key Hypothesis: the active site of an enzyme (the lock) has a specific shape in which only the precise amount of substrate (the key) will fit – forming an enzyme-substrate complex. Therefore producing a product.

All enzymes have the following 4 properties:

· All enzymes are proteins

· Enzymes are catalysts

· Enzymes are denatured by high temperatures

· Enzymes work best at a certain pH (normally 7)

The Effect of Enzyme concentration:

As long as the concentration of the substrate is much higher than the enzyme concentration, the rate of reaction is directly proportional to the enzyme concentration. This is because, as the enzyme concentration rises, the number of active sites that are available to interact with the substrate also rises, this raises the rate of product formation: -