Introduction: Hydrogen peroxide (H2O2) is a poisonous byproduct of metabolism that can damage
cells if it is not removed. Catalase is an enzyme that speeds up the breakdown of hydrogen peroxide
into water (H2O) and oxygen gas (O2).
2H2O2 + (catalase ) 2H2O + O2 + (catalase)
REMEMBER: a catalyst is a substance that lowers the activation energy required for a chemical
reaction, and therefore increases the rate of the reaction without being used up in the process.
CATALASE is an enzyme, a biological (organic) catalyst. Hydrogen peroxide is the substrate for
catalase.
*YOU MAY BE WORKING WITH HOT WATER, ACIDS AND BASES IN THIS LABORATORY.
USE EXTREME CAUTION AND WEAR GOGGLES/LAB APRONS AT ALL TIMES!
The general procedure for the lab is outlined below, and specific details for each variable follow.
GENERAL DIRECTIONS:
The assay system used in this lab consists of a filter paper disc which is coated with the enzyme and
then dropped into a paper cup (Figure 1) of substrate (hydrogen peroxide). As the catalyst breaks down
the hydrogen peroxide into water and oxygen gas, the bubbles of oxygen collect underneath the filter
(Figure 2) and make it rise to the surface of the hydrogen peroxide. The time it takes for the filter to rise
is an indication of the rate of enzyme activity.
Figure 1: Catalase soaked paper disc immersed in H2O2 and placed at bottom of cup at time 0s.
Figure 2: Bubbles of oxygen form beneath the paper disc as catalase breaks down H 2O2 causing the disc to rise.
RATE:
Rate of enzyme activity = distance / time
where distance is the depth of the hydrogen peroxide in mm and time is measured in seconds. We
will assume that each filter paper disc is coated with the same amount of catalase (except in the
investigation of the effect of enzyme concentration on enzyme activity).
The enzyme has been prepared for you as follows: peeled potato was mixed with cold distilled water
and crushed ice and homogenized in a blender for 30 seconds. This extract was filtered through
cheesecloth and cold distilled water was added. Extract concentration is arbitrarily set at 100 units/ml.
ENZYME SHOULD BE KEPT ON ICE AT ALL TIMES!
MATERIALS:
catalase, hydrogen peroxide TBA% forceps, filter paper discs, water,
ice, water baths, paper cups, marking pencils, stopwatch or timer
PLAN:
Each group will investigate and report on one variable. EVERY
STUDENT IS RESPONSIBLE FOR RECORDING THE RESULTS
OF ALL EXPERIMENTS in his/her lab report.
Refer to lab report guidelines for how to produce your lab report
and how it will be graded.
Modified from:
Source: Gen Nelson www.accessexcellence.org
Adapted for Horton Biology September 2007
Mr. J. Fuller