Effect of Acid on Enzyme Activity

Introduction

Enzymatic activity hugely depends on the environment that the reaction is occurring. Enzymes are biological substances that speed up a chemical reaction. Biological reaction occurs naturally at a speed that may not be life sustaining. In the body, hydrogen peroxide is a by-product of respiratory activity in living cells. Hydrogen peroxide is a toxic by-product that may have debilitating ramifications to the wellness of a human being. In this accord, it is imperative that hydrogen peroxide is removed as soon as it is produced by cells. As a means to eliminate the toxic effects of hydrogen peroxide, cells synthesize an enzyme, catalase to remove the by-product. Typically, catalase reacts with hydrogen peroxide to yield two molecules of water and oxygen. The reaction rate, which denotes the speed in which hydrogen peroxide is converted into less harmful products, can be measured examining the speed in which the balloon fills up with oxygen. 

Aim

The aim of the laboratory experiment is to determine the effect of acids on catalase activity.

Hypothesis

Since the optimum pH for catalase activity is 7, an acidic pH will result in a reduced enzyme activity, the conversion of hydrogen peroxide into water and oxygen. 

Lab Materials and Procedures

Lab Material

For successful completion of this laboratory experiment, the following apparatus were used:

pH paper

vinegar

balloons

plastic bottles

plastic beakers

hydrogen peroxide solution

marker for labelling the beakers

digital camera

An enzyme catalase from yeast

Procedure

The procedure is anchored on the fact that catalase will interact with hydrogen in acidic conditions. As a control for the experiment, catalase will be allowed to react with hydrogen peroxide in optimal conditions, a pH of 7, to determine the rate of the reaction. The rate of the reaction based on the experiment will then be compared to the optimum rate to determine the effect of acid pH on the effect of catalase activity.

Yeast, which is the source of catalase, will be put into half a cup of warm water. The water must be at a temperature of 37 degrees to warrant optimal enzyme activity. A permanent marker is used to label the remaining beaker from one to two. To cup one, one table spoon of 3 percent hydrogen peroxide solution was added. For the second beaker one table spoons of hydrogen peroxide was added. Subsequently, one table spoon of yeast was added to each of the cups and the change in the results was recorded. Lastly, 20 ml of vinegar was added to cup two and the change in the rate at which oxygen was collected in the balloons was recorded. Typically, cup one represented the control experiment, while cup two sought to test the effect of the introduction of vinegar (acid) to the reaction. 

Results

Results were recorded for the control experiment and the setup that sought to examine the effect of an acid on enzymatic activity of catalase. Since the experiment sought to examine the rate of the reaction, the most effective approach of determining the effect of a change in pH on the rate of the reaction is evaluating the rate at which the reactant, hydrogen peroxide, is converted into water molecules and oxygen. For cup 1, the balloon filled up quickly when yeast was introduced to hydrogen peroxide. In the case of cup 2, the balloon filled up relatively slowly. Therefore, from the experiment, it can be inferred that adding vinegar to the reactants reduced the rate of the reaction as evidenced by the reduction in the oxygen yield.

Discussion

The chemical reaction in the experiment is:

Hydrogen peroxide + vinegar + catalase yields water and oxygen molecules

The pH has an effect on the state of ionization of basic or acidic amino acid. Amino acids tend to have a carboxyl functional group, located in their side chain. If the state of ionization of the amino acid that make up a protein is altered, then the ionic bond that make up the 3D configuration of the protein is altered, in a process called denaturation. Since enzymes are proteins, the ionization effect of an acid can result in a change in the shape of an enzyme, hence making it inactive. The inactivity of the enzyme is based on the fact that enzymes interact with their respective substrates in a key-and-lock configuration. Therefore, if the shape of configuration of the enzyme changes, then a substrate cannot bind with the enzyme’s active site; hence, the entire chemical process will not experience catalysis. The bottom line here is that enzymes have an optimum pH where enzymatic activity is at the highest possible level. In this regard, if the conditions are not optimum, the shape of an enzyme’s active site is altered; thus, an enzyme cannot interact with a substrate in a key-and-lock configuration.

The results from cup one was optimal because the pH was at 7. However, in cup 2, the pH was acidic, resulting in the denaturation of the enzyme catalase, which caused a reduction in enzyme activity.

Conclusion

In conclusion, enzymes perform optimally in optimum conditions. It is imperative to note that some enzyme perform optimally in acidic conditions and other work best in a basic pH. In the case of catalase, the enzyme work best in a neutral pH. Hence, the introduction of vinegar denatures the enzyme reducing catalase activity. The rate of the conversion of the reactants to non-toxic products was relatively low when vinegar was introduced to the reaction.