Thursday, October 14, 2010

Gross and easy enzymes: Hydrogen Peroxide and Catalase

Enzyme experiments are often limited to molecular labs with expensive and sophisticated equipment.  There are however several enzymes that can be isolated very easily with minimal equipment and materials.  Catalase is one such enzyme that anyone can access for experimentation.  The process for isolating catalase, though easy, is like so many other cool biological experiments: its kind of gross.  But first, what exactly is an enzyme?  An enzyme is a protein that carries out a chemical reaction that normally would not take place.  Our bodies, along with all other organisms, are loaded with hundreds of different enzymes that control when, where, and what chemical reactions happen.  Specific types of enzymes only carry out one type of chemical reaction but can carry out that reaction hundreds of times over.  Enzymes are essentially what do the 'work' of breaking down or digesting things such as our food and then building food molecules into cells to form our bodies.  The reaction that catalase carries out is converting the potentially harmful hydrogen peroxide molecule into harmless oxygen and water molecules.  This is essentially what happens: 

Catalase enzyme + hydrogen peroxide --> catalase enzyme + water + oxygen
After the catalase breaks down hydrogen peroxide into water and oxygen, catalase is then available to carry out the same reaction again.

 Samples of heart, kidney, and liver blended organs for catalase experiment.  
The sediments at the bottom are tiny chunks that settled out.
In order for us to isolate catalase we must first locate some fresh liver.  We get all of our liver, or any other organ meats, from the local grocery store.  We then take about five to ten grams of liver (slightly smaller than a ping pong-ball) and place it in a blender with 500 ml of distilled or unchlorinated water then blend until homogeneous.  Once you have a homogeneous mixture of liver juice, or any other juice for that matter, place several drops in a test tube.  Next, add several drops of hydrogen peroxide to your liver juice test tube.  If catalase is present in your liver juice, and it should be, foaming should take place.  The foam bubbles are full of oxygen that the catalase is producing by breaking down the hydrogen peroxide.  So the more foam that is produced the more catalase is present.  You can repeat this experiment with kidney juice, or any other type of meat. 
In the picture at right I tested heart, kidney, and liver juice for catalase by mixing them with hydrogen peroxide.  From left to right we see the results for heart (no foaming), kidney (foaming), and liver (slightly more foaming than kidney).  Based on these results we know that heart tissues have no catalase, kidney has catalase, and liver has the most catalase.  So why would heart have no catalase while kidney and liver have a lot of catalase?  Well the liver and kidneys are filtering and cleaning organs so having catalase present in them would aid the cleaning of blood of harmful hydrogen peroxide molecules.  Heart on the other hand is not a cleaning organ so no catalase is present.  Other organs and tissues can also be tested in this way but the liver and kidney are the only ones we have found that contain catalase.  We have also tested plants but have only found spinach to contain catalase for some strange reason.  Why the heck would spinach have catalase?  If anyone can figure that out be sure to let me know. 
Enzymes being large complicated proteins are very sensitive to temperature and pH.  You can do more experiments on catalase by heating or cooling the liver juice to see what effects temperature has on foaming.  Try putting it on ice or boiling it.  Also, try adding a little baking soda mixed with the juice to see how the enzyme works in a basic pH solution or vinegar for a acidic pH solution.  Nearly everything you need to know about basic enzyme function can be accomplished through these simple experiments.  There are a few other enzymes that are also easy to handle in a non-lab environment that I will try to post at future dates. 

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