Enzyme Experiment Analysis

The goal of this homework is for you to develop an understanding of how the rate of activity of an enzyme can be calculated. In order to do this, you will analyze some data that was generated in a face to face biology 101 lab.

1. Read through the background about the catalase enzyme and calculating the rate of a reaction.
2. Examine the data that was produced by students during this lab. Use this data to calculate the rate of reaction of the enzyme.
3. Create the graphs described below. Graphs can be made in Excel (or another graphing program) and pasted into your assignment file. Alternatively, you can make your graph by hand and scan it or take a picture of it to insert into your assignment file.
4. Save this file as a .doc, .docx, or .pdf file only. Change the file name so that it starts with your first initial and last name at the beginning. For example, I would submit a file named lbarteelesson6assignment.doc using the link in BlackBoard.

BACKGROUND

Catalase Enzyme

This assignment investigates the function of the catalase enzyme. Catalase is found in nearly all organisms that are exposed to oxygen. It catalyzes the decomposition of hydrogen peroxide into water and oxygen gas. If you have ever poured hydrogen peroxide on a cut and watched it bubble, you have observed the activity of the catalase enzyme. You can use the amount of bubbling to measure the amount of product (oxygen gas) that has been formed. When this is related to the amount of time that has elapsed, an indication of the activity of the enzyme is produced.

This week, you will be investigating the effect of several variables on the catalase enzyme. It is important to note that the total amount of product (height of bubbles) is determined by the amount of substrate that is put into the reaction. This makes sense because the substrate is converted into the product. If more substrate is added, you can expect to get more product out at the end of the reaction. The addition of the enzyme speeds up the rate (speed) of the reaction, but does not determine the overall height of the bubbles. As more enzyme is added, the reaction should proceed faster and faster, as long as there is an excess of substrate available. If the amount of substrate becomes limiting, adding more enzyme will not make the reaction go more quickly.

The lab that this assignment is based on used blended potato extract as the source of the catalase enzyme. Hydrogen peroxide was added to the reactions and the amount of bubbling was observed. Here’s another way of showing this reaction:

Effect of pH on enzymes

The pH of a solution relates to the concentration of hydrogen and hydroxide ions in the solution. A solution with a high concentration of free hydrogen ions is acidic, while a solution with a high concentration of free hydroxide ions is basic. A solution where both types of ions are equal is neutral. Acids have pHs that are below 7 on the pH scale, 7 is neutral, and pHs above 7 are basic. Changing the pH of a solution changes the concentration of hydrogen and hydroxide ions in that solution. This can interfere with the pattern of positive and negative charges within a protein molecule, which will change the way the protein folds. The optimum pH is the value at which the enzyme functions the best. Extremely high or low pH values can result in denaturation (the loss of the three-dimensional shape), which will result in a loss of enzyme activity. The optimum pH for the human catalase enzyme is approximately pH = 7.

Reaction Rate

Remember from math classes you have taken that rate is a measurement of how quickly something is occurring. You can calculate rate by taking the amount that something has changed over the amount of time that the process has taken.  You will be calculating the rate of the catalase reaction with different amounts of enzyme added.

Once you have calculated rate for a reaction, you will create a new graph with rate on the Y axis (as your dependent variable) and your independent variable that is affecting rate on the X axis (enzyme activity is the independent variable in the graph shown below).

ASSIGNMENT

The effect of enzyme concentration on the rate of reaction

1. Create a graph showing the effect of enzyme concentration on the height of bubbles in mm over time. Consider what type of graph is the correct choice to show a change in something over time! Paste this graph below.

Calculating the Rate of the Reaction

1. Fill in the change in bubble height in the table above. Calculate the rate of the reaction and fill those values into the table as well. Make sure you look at the background information at the beginning of the assignment about calculating and graphing rate!

1. Create a graph showing the effect of enzyme concentration on the rate of this reaction. Paste this graph below.

1. What happens to the rate of the reaction as you add more enzyme? Type your answer below.

1. If you left the tubes long enough, do you think the tube with 0.5mL of potato extract would end up with the same amount of bubbles as the tube with 3 mL of extract? WHY? Assume that the bubbles do not pop and the enzyme continues to function. Type your answer below.

1. Does the rate change more quickly between 0 and 1mL of enzyme or between 2 and 3mL of potato extract? Why do you think this is the case? Type your answer below.

Effect of pH on the catalase enzyme.

1. What do you think are the contents of the control tube (control group)?
2. Why does this experiment need a control group?

1. Fill in the change in bubble height in the table above. Calculate the rate of the reaction and fill those values into the table as well. Make sure you look at the background information at the beginning of the assignment about calculating and graphing rate!

1. Create a graph showing the effect of pH on the rate of this reaction. Paste this graph below.

1. What is your conclusion about the effect of pH on the catalase enzyme? Type your answer below.