Enzyme Reaction Rate, Lab Report Example

Introduction

Enzymes are substances that bind to a substrate molecule in order to catalyze a reaction and thereby convert the substrate into a product substance. Laboratory experiments can re-create an enzyme reaction using purified compounds. Although, the conditions that occur inside a cell are not identical to a test tube reaction, the conditions can be identified. A chemical reaction occurs at a given rate, which is calculated by the number of molecules of the product that is produced per minute. The reaction is also dependent on the concentration of the enzyme and substrate. For instance, an increase in the concentration of both the enzyme and substrate results in a faster reaction time. Therefore, we can expect that the rate of the reaction increases with increasing substrate concentration, but only up to a certain point, which can be referred to as the maximum rate.  There are other factors that affect the rate of enzyme reactions, such as pH, temperature and inhibitors. The pH is a measure of the amount of Hydrogen ions in a solution. In regard to enzymes, high salt concentrations can affect the shape of enzymes and thereby affect the binding of enzyme to the substrate.Temperature also affects enzyme activity.  Increasing temperatures can increase the collision of enzymes and substrates and high temperatures can result in denaturation of enzymes. Inhibitors act to prevent enzyme reactions, and therefore the addition or increase of an inhibitor in the solution would cause a decrease in the reaction rate. (DCCD)

Peroxidase is an enzyme that can be extracted from plants. This type of enzyme is stable and easy to use in a laboratory setting, as well as a good enzyme to use to compare among different species. In order to determine the effect of different factors on the rate of an enzyme reaction, pH, temp, and an inhibitor was tested against enzyme reaction rate.  It was hypothesized that as the pH increased, the activity of the enzyme increased until reaching an optimum pH range at pH7 (neutral).  In addition, it was further hypothesized that as temperature and inhibitor, such as Hydroxylamine (HONH2)increased, the activity of the enzyme reaction rate would increase as well.

Materials and Methods

The methods were followed using the laboratory manual provided.

Results

The results of the experiment are illustrated in Figure 1, 2, and 3.  As seen in Figure 1, the reaction did not occur when using the inhibitor.  Figure 2 shows an increase in the rate of the reaction with increasing temperature.  Figure 3 shows an increase in the reaction rate at pH levels 8-9 compared to pH levels 4-5.

Discussion

The results of the experiment correlate with the hypothesis for the rate of the enzyme reaction for pH, temperature, and inhibitor. The enzyme rate of the reaction showed an increase during pH levels at 8-9. The pH levels 4-5 showed a slower reaction rate. This corresponds with the hypothesis and indicates that enzyme activity is more efficient at pH levels closer to the optimum pH, which is at 7 or neutral.  A pH level at 4-5 is very acidic and contains more hydrogen ions, which could cause binding issues to the substrate.  In addition, the experiment showed an increase in the reaction rate with increasing temperature as well.  As the temperature in the water bath increased, the reaction rate also increased.  The optimum temperature was not identified, as there was no equilibrium reached.  The rate kept increasing and did not slow during the reaction.  The results for the inhibitor correspond with the hypothesis.  It was hypothesized that the rate would decrease with an inhibitor.  There was no activity observed when using the Hydroxylamine (HONH2) inhibitor. The Hydroxylamine (HONH2) prevented the enzyme and substrate binding.

Peroxidase showed to be a good enzyme for this experiment and illustrated the factors that affect enzyme activity.  Peroxidase can be used in other experiments, such as identifying the amount of peroxidase in different types of plants in different types of habitats.  This type of experiment can illustrate the need for peroxidase based on conditions in the environment. The current experiment may have had some human error with temperature regulation that could present the reason for the lack of an optimum level in the temperature for reaction activity.

References 

DCCD.  BIOL 1406 Properties of Enzymes: Peroxidase, A Case Study.  Retrieved from: http://www.dcccd.edu/SiteCollectionDocuments/DCCCD/Docs/Departments/DO/EduAff/Core/Assessment%20Methods/Enzyme_lab%20report_final.pdf