Investigating the effect of substrate concentration on an enzyme-catalysed reaction

The substrate concentration in an enzyme catalysed reaction affects how much product is made.

Catalase is an enzyme that increases the breakdown of hydrogen peroxide, a toxin produced as a bi-product of reactions in cells. The reaction of catalase is shown below:

2H2O2 - > 2H2O + O2

Catalase is found in high concentration in raw potatoes.

Apparatus and reagents

Freshly cut potato cylinders

Pestle and mortar

Specimen tubes/test tubes

Stock solution of hydrogen peroxide 10 vol ( labelled stock solution

Filter paper discs

Forceps

Stopwatch

Syringe

Distilled water

Paper towel

Method

1. Grind a 2cm piece of potato cylinder with 5 cm3 of distilled water to make a smooth paste containing the enzyme.

2. Place 10cm3 of H2 O2 in a specimen tube/ test tube.

3. Using forceps, dip a filter paper disc into the enzyme suspension, tap off the excess.

4. Drop the filter paper disc into the hydrogen peroxide solution and measure the time, to the nearest second, that it takes from striking the surface to sink to float up to the surface again.

5. Remove the disc from the tube using forceps and discard.

Risk assessment