An Investigation of Enzyme Catalase

Project #3205 on iSENSEProject.org

Introduction

Enzymes are catalytic proteins that speed up the rate of chemical reactions that would otherwise happen more slowly. A catalyst is a chemical agent that changes the rate of a reaction without being consumed by the reaction. You have hundreds of different enzymes in each of your cells. Each of these enzymes is responsible for one particular chemical reaction that occurs in the cell.

In this lab, you will study catalase, an enzyme that is found in the cells of many living tissues, including those of plant, animal, and even fungus. Catalase speeds up a reaction that breaks down hydrogen peroxide, a toxic chemical, into 2 harmless substances-water and oxygen:

2H2O2  2H2O + O2

You may be surprised to find out that hydrogen peroxide is produced as a waste product in every cell of your body. It is a byproduct of many normal chemical reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned and die. In cells, the enzyme catalase works on its substrate hydrogen peroxide converting it to harmless water and oxygen.

The rate of this reaction can be determined by measuring the amount of oxygen produced. Yeast cells are encapsulated in sodium alginate, a non-toxic, easily obtainable, algal extract, to form uniform spheres. These spheres are dropped into H2O2 and the oxygen created as a byproduct in the reaction builds up on the sphere, causing it to float. The time it takes for the spheres to rise to the surface of H2O2 is measured. Depending on the catalase solution some of the reactions will happen faster than others, producing oxygen faster and the sphere will float sooner.

Some background on Sodium Alginate:

Sodium alginate is a non-toxic hydrophilic polysaccharide that is used as a thickening agent in foods such as ice cream, yogurt, and cake mixes because it helps to emulsify oil and water and give a smooth texture to foods. It is used by some chefs to make flavor “pearls” or “caviar” and it is also used to encapsulate yeast in the production of wine.

When sodium alginate, a hydrophilic polymer, comes in contact with CaCl2, sodium ions are replaced with calcium. This leads to cross-linkages between the polymer chains and an insoluble gel is formed. If spheres with “tails” form when the yeast-sodium alginate solution comes in contact with the CaCl2 the yeast-sodium alginate solution may be too thick. If this is the case just thin it out with a bit of dH2O.