Limon Trust: Enzyme Lab 11/4/2013

Introduction

In this lab we studied the effects of enzymes and their effect on various substances. An enzyme is a naturally occurring particle that speeds up a reaction. The enzyme takes in the reactants, adds a phosphor ion to the reactant, thus motivating it to do work with less activation energy. The overall release of free energy is the same even with the presence of the enzyme, which makes enzymes nifty. The substrate is the substance the enzyme acts upon. In this case, it was the yeast and the hydrogen peroxide. In this procedure, we tested for the concentration of hydrogen peroxide with an indicator KMO3.

Enzymes function at optimal temperatures and optimal pH levels. At an optimal temperature, the rate of the reaction is the highest. At optimal pH, the reaction rate is also the highest. In this experiment we conducted a test for optimal pH and see how the enzyme would react if we injected acid into the solution.

Also present in this experiment are catalysts. A catalyst is, in this case, a substance that affects the rate of the reaction. A catalyst can either inhibit or increase the reaction rate by lowering the activation energy. An enzyme is just a type of catalyst.

Procedure

Baseline) First we added 10 mL of 1.5% hydrogen peroxide solution to a beaker. We then added 1 mL of water instead of enzyme solution. After we added 10 mL of sulfuric acid to stop the reaction. We removed a 5 mL sample of the solution into another beaker. We added Potassium permanganate to the solution drop by drop until solution remained a pinkish color.

Uncatalyzed hydrogen peroxide reaction) Here we placed about 15 mL of 1.5% hydrogen peroxide solution in a beaker. We let it sit overnight. The following day we added sulfuric acid to the solution. We took a 5 mL sample and added potassium permanganate drop by drop until a pinkish color remained.

Enzyme catalyzed hydrogen peroxide reaction) Here we placed 10 mL of 1.5% hydrogen peroxide solution in each of 6 beakers. We added an enzyme to each solution in this case yeast. We let each beaker sit for 10, 30, 60, 90, 120, 180, 360 seconds respectively. We added sulfuric acid after time was up for each beaker. Then we took a 5 mL sample from each beaker and added potassium permanganate drop by drop using a burette until the solution for each beaker remained pink.

Methods

Baseline) First we established a base line. Without adding catalase to the Hydrogen peroxide solution, instead water we could more easily determine the amount of hydrogen peroxide present at the beginning of the reaction. By adding the sulfuric acid it would stop any spontaneous reaction from proceeding. By taking a sample and then adding potassium permanganate we can determine the amount of hydrogen peroxide present after the reaction has stopped. The amount of potassium permanganate added is proportional to the amount of hydrogen peroxide present. When the solution turns pinkish it represents a bit leftover of potassium permanganate that did not dissolve hydrogen peroxide.

Uncatalyzed hydrogen peroxide reaction) We left a solution of hydrogen peroxide overnight without adding a catalase to determine the rate of a spontaneous reaction. The conversion of hydrogen peroxide to water and oxygen. The next day we added sulfuric acid as it stops the reaction. We took a sample and added potassium permanganate to determine the amount of hydrogen peroxide that did not react or decompose into water and oxygen. This part showed the rate of an uncatalyzed hydrogen peroxide solution decomposition.

Enzyme catalyzed hydrogen peroxide reaction) The yeast added to each solution was the enzyme that will speed the reaction or decomposition of hydrogen peroxide to water and oxygen. And each beaker was left to proceed in its reaction for differing times before sulfuric acid was added to stop the reaction. After we took samples of each of the differing time beakers and added potassium permanganate to determine the amount of hydrogen peroxide that was left. This part gave showed the amount of hydrogen peroxide left after being catalyzed by yeast at differing times in this case 10,30,60,90,120,180,360 seconds.

Discussion

Some mistakes will be accounted for in this part of the lab. As you can see, our data does not correspond with the purpose of the lab. Our data table should have shown an inverse relationship between the time and the amount of KO4 we used in our experiment. This only happens from second 60 to 90 and then from second 180 to 360. The increasing amounts should have been higher than its preceding ml of KO4. We assumed that inaccurate samples were taken of the substances. For example, we might have taken a 10 ml sample rather than a 5 ml sample.

However, other groups have gotten the ideal inverse relationship of H2O2 decomposition with the time the enzyme got to react with the substrate. Ideally, the more the substrate got to interact with the enzyme, the less KO4 would be used to indicate the presence of H2O2. This is true for our graph but only at the 360 second point. Everything else is a little off.

Conclusion

The decomposition rate of the hydrogen peroxide is directly related with the enzyme activity. This is because enzymes speed up reactions by lowering the activation energy needed for the reactants to be converted to products. Although our data does not conform to the accepted trends, we know that the longer an enzyme is allowed to act on a substrate, more substrate will be catalyzed. Since more substrate is catalyzed, it will take less indicator to find how much substrate is left.

Graphs and Data)

Our data