The Catalytic Enzymes: How Hydrogen Peroxide Catalyses

Purpose: The purpose of the lab is to learn the functions of enzymes, especially in chemical reactions, and to determine if, over time, enzymes activity changes in rate. More specifically, the lab was performed to learn the use of catalase in hydrogen peroxide to create a chemical reaction, to follow correct lab procedure, and to accurately measure and record data.

Materials:

1. 6 Clean Test Tubes
2. Calorimeter-which is comprised of a Graduated Cylinder, Cotton Ball Plug, and Temperature Probe (which is connected to the Lab Pro which in turn is connected to the Computer for compiling data)
3. Cotton Ball Plug
4. Forceps
5. Graduated Cylinder
6. Hydrogen Peroxide
7. Pieces of Paper Towel
8. Raw and Boiled Samples of Carrot
9. Raw and Boiled Samples of Liver
10. Raw and Boiled Samples of Potato
11. Test Tube Rack
12. Writing Utensil (to observe and label with)

Discussion:

The observations from the lab match the description in the background of catalase's decomposition of the hydrogen peroxide. The raw, room temperature samples formed many bubbles (for an explanation of how read a sentence or two down), while the boiled temperatures did not (those samples formed little or no bubbles) because enzymes, which are acting as catalysts in this experiment, work best at room temperature, the temperature of the body. A higher temperature will affect the efficiency of the enzymes as catalysts in the reaction and therefore cause not as many bubbles because of the lethargy of the chemical reaction (the decomposition of the hydrogen peroxide, which causes the bubbles). The catalase, in this experiment, is an enzyme acting as the catalyst. There were bubbles when the catalase was added because the catalase is creating a chemical reaction, making the hydrogen peroxide (2H202) decompose into 2H20 (water) and 02 (oxygen in gas form) by lowering the activation energy needed to start the reaction. The oxygen, in gas form, is what is causing the bubbles, when it escapes after being broken down from the hydrogen peroxide. The catalase in the plant and animal tissues is the enzyme that is acting as the catalyst in the experiment. Plant tissues have a cell well made of cellulose while it is absent in animal cells. It is what is causing the reaction to happen, as it decomposes the hydrogen peroxide. Hydrogen peroxide, when poured on a wound, begins to bubble. Since catalase acting with hydrogen peroxide creates bubbles by breaking the hydrogen peroxide down into water and oxygen gas, it is logical to assume that there is catalase in human tissues.

The average total temperature change over the trials from the lowest to the highest temperatures was 10.7 degrees Celsius. The average temperature change from zero to three hundred seconds over the trials was 9.25 degrees Celsius. If the graph reaches a plateau, then the reaction rate is neither negative nor positive; it is zero, as the rate is steady, constant, and not changing. The plateau means the reaction is over. This experiment is an exothermic reaction. One might notice the heat radiating out from it if hands were placed on it. If the temperature originally increases, but then decreases, it means that the reaction happens very quickly and the heat is expelled in the exothermic reaction rapidly. When the heat is gone, the substance cools down, reducing the temperature. If a graph decreases after a sudden increase or reaches a plateau, then the reaction did not take the whole three hundred seconds to complete, it may have been finished much earlier. The source of heat in this reaction is the catalase decomposing the hydrogen peroxide. All energy resulting from biochemical reactions does appear as heat, but there are different ways for it to be used in a chemical reaction. In an exothermic reaction, the energy is released and transferred to the surroundings in the form of heat, and in an endothermic reaction, the heat energy is absorbed from the surroundings.

Conclusion:

Enzymes, acting as catalysts, are crucial in the group's study of chemical reactions. In this experiment, the enzyme acting as a catalyst was the catalase, found in plant and animal cells. It was decomposing the hydrogen peroxide, which normally splits into water and oxygen gas in water, but it is an extremely slow process, so cells produced catalase to reduce possibly toxic levels of hydrogen peroxide. The group learned how to set up and run a proper experiment, as well as recording data on scientific computer programs. These graphs provided the students with many helpful insights into rates of enzyme activity and function. The main reaction on which the experiment focused on to was the decomposition of hydrogen peroxide by the catalase, or 2H2O2----->2H2O+O2+Energy (heat). The arrow is the catalase. There were some observations that were perceived during the experiment, notably bubbles forming on the top of raw samples, and little or none with the boiled samples. Some of the samples sank and some floated, while others started dissolving or fizzing. And with the raw liver sample, a pus-like liquid formed a film and trapped the foaming, fizzing bubbles below it. Also with the raw liver sample, foam formed and almost flowed out of the entire test tube. There were some sources of error, though. Only two trials were performed instead of the desired three, and some raw liver sample was stuck on the sides of the cylinder as it was poured down, skewing the proportions of sample (affecting the amount of catalase) to hydrogen peroxide.