Investigating Factors That Affect Rate of Enzyme Action

 

Denice Gamper

Bard High School Early College, Manhattan

Summer Research Program for Science Teachers

August 2010

 

 

Subject:  Living Environment/Biology

Grade Level: 9th and 10th

Unit: Biologically Important Molecules

Duration:  8 Fifty minute class periods

        a) Part 1

       b) Part 2

Purpose:  Students investigate factors that affect the rate of enzyme action.  Catalase will be used as the model enzyme to investigate the factors that affect rate of enzyme action.

Objectives: Students will be able to (SWBAT):

Prior Knowledge: Students will have an understanding of the four classes of biologically important compounds (ie. carbohydrates, fats, proteins and nucleic acids).  In particular, students will have an understanding of the different levels of protein structure as well as the various functions of proteins

Essential Questions:

  1. What is an enzyme? How do enzymes affect a chemical reaction?
  2. What are the general characteristics/properties of enzymes?
  3. Describe the two models used to explain the catalytic activity of enzymes
  4. What are the factors that affect the rate of enzyme action?
  5. Explain how temperature affects enzyme activity?  What is meant by optimum temperature?
  6. Explain how pH affects enzyme activity?  What is meant by optimum pH?
  7. Explain how changes in enzyme or substrate concentration affect an enzyme's behavior?

Preparation and Procedure: 

Part 1: WebQuests (3 class periods)

1.      Students will complete a K-W-L chart on enzymes.

2.      Students will work in groups of two or three to complete WebQuests that explore the

         a) structure and function enzymes.

         b) models used to explain the catalytic activity of enzymes (ie. Lock and Key and Induded Fit models).

         c) characteristics of enzymes.

         d) factors that affect the rate of enzyme activity.

3.      Use the Essentials Questions to guide students during the WebQuest.

4.      Teacher Tip: 

         a)      Print out hard copies of each of the websites used for the WebQuests in the event that students are unable to connect to the Internet.

                 For a class size of twenty-four students working in groups of 3, print out eight copies of each website to be used in during the WebQuests.

         b)      For each of the four topics being explored limit the number of websites that address each topic to only two.  

5.    Students will work in groups of two or three to formulate potential experimental questions to test various factors that affect the rate of enzyme activity.  Experimental questions will be posted on either newsprint or an overhead transparency.

 

Website Resources:
1. Animations/Tutorials

          a)     Lew-Port’s Biology Place – Enzyme Activity

          b)    The Biology Place:  LabBench Activities – Lab 2:  Enzyme Catalysis

         c)    Interactive Concepts in Biochemistry – Interactive Animations:  Enzyme Specificity

       d)  Biology Mad - Enzymes

       e)  Wonder WhizKids:  Biology – Molecules of Life: Proteins and Enzymes

2. WebQuest Resources

      WebQuest.Org Website that describes how to develop and implement a WebQuest in the classroom.

 

Part 2: Inquiry Based Lab Activity (5 class periods)

Background Information:

      Catalase will be used as the model enzyme to investigate how temperature, enzyme or substrate concentration, salt concentration and/or changes in pH affect the rate of enzyme action.  Hydrogen peroxide is a toxic byproduct of metabolism.  Catalase speeds up the breakdown of hydrogen peroxide into water and oxygen gas.  This enzyme can be found in plant and animal cells as well as aerobic bacteria.  The generation of oxygen gas bubbles can be used to quantitatively assess the affect of various environmental conditions on the rate of catalase activity.

1.             1.   Students will work in groups of two or three to:

         (a) formulate a hypothesis to answer one of the experimental questions posed by the class at the end of Part 1.

              (1)   Homework: Students will complete their procedures at home. Students may conduct research using the Internet in order to design their procedure.

        (b) Students will review each other’s procedures in class before deciding on a final procedure to submit to the instructor for approval.

2.      Once the instructor has approved the procedure students will carry out their experiment during their assigned laboratory period.

        (a) Teacher Tips for Laboratory Preparation: 

·         When reviewing student experimental procedures be sure that:

               (1)   potato samples being tested are the same size

                     (a)   Students can use cork borers to obtain potato samples and trim them using a scalpel or razor blade to the desired length.

               (2)   potato extract tends to give more consistent and reliable results.

                    (a)   Use 4-ply cheesecloth obtained from a science supply company (E&K Scientific) to filter the extract.

                    (b)   Be sure to keep the potato extract on ice at all times.

              (3)   students have included a control in their experimental design

              (4)  students are testing only one variable

·      Some factors that students may investigate are:

              (1)   Changes in temperature

              (2)   Effect of different salt concentrations (ie. 1%, 2%, 3%, etc)

              (3)   Effect of enzyme concentration

                    (a)   The initial extract can be considered 100% catalase.  Students can perform a serial dilution by mixing the extract with deionized water to obtain concentrations of 80%, 60%, 40%, and 20% catalase.

                    (b)   Be sure to keep the peroxide solutions in a brown solution bottle. 

             (4)   Effect of substrate concentration

                        Students can perform a serial dilution using 40 volume (12%) cosmetics grade hydrogen peroxide to obtain lower concentrations of hydrogen peroxide.

                        Cosmetics grade hydrogen peroxide can be purchased from a beauty supply store.  Be sure to use deionized water when performing these dilutions.

             (5)   Effect of pH

                      Students should use solutions that have pH values of 1, 3, 5, 7, 10, and 12.  Solutions with these pH values can be prepared using 1M HCl and 1M NaOH.

                       Be sure to use pH test strips to verify the pH of each test solution.

 

  • Safety: Students will be expected to include a list of safety precautions as part of their experimental design.

                           (a) Teacher Tip:  Be sure students include safety procedures/precautions for the following:

                                  (i) handling of hot objects and hot plates,

                                  (ii) use of thermometers

                                  (iii) checking glassware for chips, cracks and stars

                                  (iv) cleanup and disposal of broken glassware

                                  (v) cleanup and disposal of spilled liquids

                                  (vi) disposal of unused liquids

                                  (vii) handling of sharp objects like scalpels or razor blades

                                  (viii) use of personal protective equipment:  goggles, apron or lab coat, latex or nitrile gloves

                                      (some students may have an allergic reaction to latex so it is advisable to have a non-allergenic substitute)

    3.   The students will be given time during the class period following the laboratory activity to summarize their data and present their results to the class using newsprint or overhead transparencies.  Students will also be expected to complete the “L” section on the K-W-L worksheet.

     

     

    4.      Teacher Preparation for Part 2:

              a) Possible experimental procedures for this laboratory activity can be found by reviewing the following:

    ·         Topic 5:  Enzymes - Catalase

                  Smith College Biology Department

    ·         The Properties of Enzymes – A Study of Catalase

                 Cornell Institute for Biology Teachers:           

    ·         Science Assessment Prompt - Course: Biology – Enzyme Catalyzed Reactions

     

    Materials:

    Part 1:  WebQuests

    ·      K-W-L worksheet for each student on enzymes and characteristics of enzymes

    ·    WebQuest Worksheets for enzyme structure and function, models used to explain the catalytic activity of enzymes, characteristics of enzymes and factors that affect rate of enzyme activity

    ·    Print copies of websites used for the WebQuests

    ·    Laptop computers with Internet access

    ·    LCD projector

    ·    Overhead projector

    ·    Newsprint or an overhead projector and transparencies to record student responses to the K-W-L worksheet.

     

    Part 2 – Inquiry Based Lab

    test tubes

    gloves

     

    test tube rack

    goggles

     

    test tube holder

    Stop watch

     

    Sharpie marker

    apron

     

    10 mL graduated cylinders

    disposable transfer pipettes

     

    Potato pieces or potato extract

    1M hydrochloric acid

    Mortar and pestle

    1M sodium hydroxide

    Cosmetics Grade Hydrogen peroxide - 40 volume (12% hydrogen peroxide)

    vinegar

     

    Sodium chloride

    400-mL beakers

     

    wash bottle with deionized water

    Ice

    30 centimeter ruler

    Alcohol thermometers

     

    hot plates

    Newsprint for presentation of results

     

    blender

    graph paper

    4-ply cheesecloth

    ice bucket

    cork borer with 4 or 6-mm inside diameter

    weighing boats

         Suggestions for Assessment:

·    Evaluate the completion of the WebQuest worksheets.

·    Evaluate the “L” column for the K-W-L worksheet.

·    Evaluate the group presentation of data and results.

 

National Science Education Standards:

1.      National Science Educations Standards – Grades 9 to 12

a)     Science as Inquiry:

·         Abilities necessary to do scientific inquiry

·        Understandings about scientific inquiry

b)      Life Science:

·     The Cell

c)      K-12 Unifying Concepts and Processes:

·     Evidence, models, and explanation

·    Change, constancy, and measurement

 

 

New York State Standards: 

1.      Standard 1:  Students will use mathematical analysis, scientific inquiry, and engineering design, as appropriate, to pose questions, seek answers, and develop solutions.

a)      Key Idea 1 - The central purpose of scientific inquiry is to develop explanations of natural phenomena in a continuing and creative process.

·         Performance indicators 1.1, 1.2, 1.3

b)      Key Idea 2 - Beyond the use of reasoning and consensus, scientific inquiry involves the testing of proposed explanations involving the use of conventional techniques and procedures and usually requiring considerable ingenuity.

·         Performance indicators 2.1, 2.2, 2.3, 2.4

c)      Key Idea 3 - The observations made while testing proposed explanations, when analyzed using conventional and invented methods, provide new insights into natural phenomena.

·         Performance indicators 3.1, 3.2, 3.3, 3.4, 3.5

2.    Standard 4:  Students will understand and apply scientific concepts, principles, and theories pertaining to the physical setting and living environment and recognize the historical development of ideas in science.

a)      Key Idea 1 - Living things are both similar to and different from each other and from nonliving things.

·        Performance Indicator 1.2 - Describe and explain the structures and functions of the human body at different organizational levels (e.g., systems, tissues, cells, organelles).

1)      Major Understandings 1.2h

         b)      Key Idea 5 - Organisms maintain a dynamic equilibrium that sustains life.

·       Performance indicator 5.1 - Explain the basic biochemical processes in living organisms and their importance in maintaining dynamic equilibrium.

                 1)      Major Understandings 5.1f and 5.1g