Name: ______Biology Lab – BiochemistryMs. Czuprynski

The Effects of Temperature on the Enzyme Catalase extracted from Potato

INTRODUCTION:

In the human body proteins are essential for survival. There are special proteins called enzymes that are constantly at work digesting food, metabolizing energy, assembling molecules, and fighting off infections. Without enzymes, these important biological reactions would not occur at a rate fast enough to keep us alive.

The main function of enzymes is to act as a catalyst and speed up the rate of chemical reactions. They do this by lowering the activation energy needed to start a chemical reaction. Another important fact about enzymes is that they are very specific about the particular reaction that they can catalyze. The reason they are so specific is that they all have a particular shape and will only fit with certain substrate molecules. Also, enzymes are not used up in a reaction and can be used over and over again.

All living things are chemical factories that are driven by chemical reactions. Enzymes affect the rates of these reactions. Enzyme activity is affected by pH (how acidic something is) and temperature. When a protein's temperature is too high, the hydrogen bonds that holds the protein's shape come apart and the protein is denatured (inactive / breaks down).

In this lab, we will use the enzyme catalase that has been extracted from potatoes. Catalase, pay special attention to the – ase ending, is an enzyme found in fruits, vegetables and animal tissues / cells. Its purpose is to destroy toxic substances that invade cellular tissue. The substrate molecule is hydrogen peroxide (H2O2). Catalase will act upon this substrate and speed up the break up of hydrogen peroxide several thousand times what it would normally do on its own. The reaction is as follows: H2O2 → 2H2O + O2

(liquid)(gas)

So why are we doing this lab?

Students will be able to…

  • Determine how an enzyme affects the rate of a chemical reaction
  • Experimentally examine how temperature affects enzyme activity
  • Describe the relationship between enzyme structure and function

PRE-LAB QUESTIONS:

1. What is an enzyme?

2. What is the purpose of adding enzymes to chemical reactions? In other words what affect do enzymes have on chemical reactions?

3. What are two factors (mentioned in this lab) that affect enzyme function?

4. What does it mean if a protein (or enzyme) is denatured?

5. What is the immune system and how does it use hydrogen peroxide to fight off infection?

6. Define the following terms:

□Catalyst: ______

□Activation Energy: ______

□Substrate: ______

□Catalase: ______

MATERIALS:

Hot PlateTest TubeTest Tube Holder

Ruler3% Hydrogen Peroxide SolutionPotato

PROCEDURE:

A. Construct a Baseline

  1. Write a hypothesis (If hydrogen peroxide is added, then…)
  2. Place potato pulp in a large test tube
  3. Add 4 mL of a 3% Hydrogen Peroxide solution. Gently tap the test tube to mix the potato and peroxide. BEGIN TIMING.
  4. Place the test tube in the rack and notice the formation of foam. After 1 minute, measure the height of the foam (above top of potato pulp). Enter this in your data table.
  5. Continue to let the foam form – measure and record the height of the foam at 2, 3, 4 and 5 minutes. Enter each height in your data table.
  6. Clean and rinse out your test tube. (liquid in sink, potato in trash)

PART A: Measuring enzyme activity through foam height in a test tube

1 Minute / 2 Minutes / 3 Minutes / 4 Minutes / 5 Minutes
Height of Foam (cm)

Part B. Measuring effect of temperature on an enzyme through height of foam in a test tube

□1. Write a hypothesis (If hydrogen peroxide is heated / cooled, then…)

□2. Place potato pulp in a large test tube to a depth of about 2 cm.

□3. Place the test tube in a water bath of 10oC for 2 minutes.

□4. Add 4 mL of a 3% Hydrogen Peroxide solution to the test tube. BEGIN TIMING.

□5. After 1 minute, measure and record the height of the foam. Enter this in your data table.

□6. Continue to let the foam form – measure and record the height of the foam at 2, 3, 4 and 5 minutes. Enter each height in your data table.

□7. REPEAT STEPS 1 – 5 by placing the test tube in a water bath of 30oC and 80oC

□7. Clean and rinse out your test tube. (liquid in sink, potatoes in trash)

Part B. Measuring effect of temperature on an enzyme through height of foam in a test tube

Height of Foam (cm) / 1 Minute / 2 Minutes / 3 Minutes / 4 Minutes / 5 Minutes
10oC
30oC
80oC

FORMAL LAB REPORT:

A. INTRODUCTION:

Be sure to describe…..

  • what enzymes are and how they work
  • how they affect the rates of chemical reactions / how they affect activation energy
  • two factors that affect their function
  • what it means if a protein (or enzyme) is denatured
  • what the immune system is and how it uses hydrogen peroxide to fight off infection
  • what is the purpose of this lab

 In other words use prelab questions and put into a background paragraph

B. HYPOTHESES:

  • “If….then” statements for both part A and part B

C. METHODOLOGY:

  • Materials List
  • Summarize what was done in lab.

D. DATA: Be sure to use rulers and label and title all charts and graphs

PART A

  • Redraw data table from part A
  • Construct a graph of the data from part A → Time (independent variable) is on the X-axis and foam height (dependent variable) is on the Y-axis.

PART B

  • Redraw data table from part B
  • Construct a graph of the data from part B→ Time (independent variable) is on the X-axis and foam height (dependent variable) is on the Y-axis. You will have 3 lines on the same graph (1 for each temperature  MAKE A KEY)

E. CONCLUSION:

  1. Do you accept or reject your hypothesis for part A? Justify your answer.
  2. Analyze your data from part A. What does your data “tell you?” In other words how does the measurement of foam indicate the activity of the enzyme?
  3. Do you accept or reject your hypothesis for part B? Justify your answer.
  4. Analyze your data from part B. What does your data “tell you?” In other words, what effect did temperature have on the rate of enzyme activity?
  5. Using what you now know about proteins, enzymes and temperature, explain why having a high body temperature (over 105oF) can be dangerous.
  6. Discuss any experimental difficulties (if any)