Materials

• Beef liver
• Hydrogen peroxide
• Test tubes, small graduate cylinders, tube racks, forceps
• An array of prepared physical and chemical materials.

Directions

What Affects Enzymes

Introduction:

In class, you will observe a typical, but important, enzyme reaction using fresh beef liver and the liquid hydrogen peroxide (H₂0₂). The enzyme responsible for the reaction is called catalase and it is found in large amounts in all oxygen-breathing creatures, including you. The enzyme's main function is to destroy H₂0₂) which is formed as a byproduct of certain natural chemical reactions in the body, but which is also highly toxic. Without a reliable and steady supply of catalase in the body, H₂0₂ would be deadly!

Because we rely on catalase so much, we are quite interested in how it works, and in what controls it's activity. In this lab you will be asked to design and carry out an experiment to identify one factor that affects catalase activity. Your goal will be to either speed up or slow down the rate of catalase activity. Previous research has indicated that most enzymes are sensitive to many different physical and environmental factors. You are to pick one environmental factor that you can alter and control and, by experiment, decide what affect the factor has on catalase activity.

HOW TO MEASURE CATALASE ACTIVITY: For this lab you will be using small pieces of beef liver as your source of catalase. Liver is an organ rich in lots of enzymes, including catalase. To test catalase activity, you will be pouring 2ml of H₂0₂ over a piece of liver in a 20ml. test tube and observing the reaction.

As in most experiments, it is important to be able to collect some sort of measurable data. For this study, it is suggested that you use a simple scale of "0-6" to measure how intense the reaction is. Assume that a fresh piece of liver and 2ml of H202 at room temperature produces a reaction rate of "4" and that no reaction at all rates a "0". We will discuss this more in class.

DUE DATE: Hand in both the report and the original experimental design summary two class periods from the day of the experiment. We will spend a few minutes each period up until the due date, discussing how to do a good write-up. Drafts of the report can be reviewed ahead of time, if you wish.