Enzymes in Action© Student Handout and Key

Enzymes are specialized proteins that catalyze or speed up chemical reactions within cells. The substance upon which an enzyme acts is called a substrate. Substrates are small molecules.

Enzymes:

   • Accomplish catalysis without being consumed in the reaction.

   • Catalyzes a specific chemical reaction. 

The Enzyme in Action Kit© allows your students to explore how enzymatic reactions occur. They will use the model pieces in the kit to:

   • Simulate enzymatic actions.

   • Explain enzymatic specificity.

   • Investigate 2 types of enzyme inhibitors used in regulating enzymatic activity.

   • Examine how an enzyme may affect activation energy.

 

EAK Student Handout

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Student Handout

 

Introduction

 

Enzymes are specialized proteins that catalyze or speed up chemical reactions within cells. The substance upon which an enzyme acts is called a substrate. Substrates are small molecules.

Enzymes:

   • Accomplish catalysis without being consumed in the reaction.

   • Catalyzes a specific chemical reaction. 

The Enzyme in Action Kit© allows your students to explore how enzymatic reactions occur.

 

Catabolism

Model pieces needed

gray A foam piece
without stickers
green B1 and B2
foam pieces
orange C1 and C2 foam pieces

1. The gray foam piece is a model of an enzyme. Place it with the A label facing up. Assemble the two green pieces (B1 and B2) into a single unit to model the substrate in this reaction.

2. Draw and label the enzyme and substrate before the enzymatic action.

 

 

 

 

 

 

3. In this first metabolic action, the enzyme will act on the substrate to break it apart. Experiment with the pieces to model how the enzyme and substrate might interact.

 

4. The substance an enzyme acts upon is referred to as the _____________________________.


5. Place an "X" on the drawing of the enzyme and substrate you created on page 1 to show where the substrate binds to the enzyme.

The part of the enzyme that binds the substrate to be acted on is referred to as the active site.

Once the substrate is locked into the enzyme, the two green substrate pieces may be easily pulled apart. This type of metabolic process is called catabolism (the breaking down of complex molecules into simpler molecules).

6. Draw and label the enzyme, products and active site after enzymatic action.

 

 

 

 

 

7. Although the substrate model changed in this reaction, what changes did you observe in the model of the enzyme during this reaction?
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8. Why do you think it is an advantage for the enzyme to remain unchanged while catalyzing a chemical reaction?
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Note: A real life example of catabolism occurs when the enzyme sucrase breaks down the substrate sucrose into glucose and fructose (monosaccharides).

9. Given what you now know about catabolism, identify the following components in the model illustrated below: enzyme, substrate, products and active site.

Induced Fit Model of Enzyme Action

In 1958 scientist Daniel Koshland, Jr., PhD., proposed the induced fit model to describe enzyme-substrate interaction. This model suggests that enzymes are flexible structures in which the binding of the substrate results in small changes to the shape of the active site, maximizing its interaction with the substrate.


10. Describe how the foam catabolism model illustrates the induced fit model of enzyme-substrate interaction.
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11. Explain the difference between catalysis and catabolism.
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Anabolism

Enzymes may also bring substrates together to form a final product. This metabolic process is called anabolism (the building of complex molecules from simpler molecules).


12. Use the gray foam piece and the orange foam pieces (C1 and C2) to simulate an anabolic process. The
orange pieces should not be assembled prior to the anabolism action.


13. Sketch and label the enzyme and substrate prior to enzyme action in the space below.

 

 

 

 

 

 

14. Place the small pointed orange piece (C2) into the enzyme. Join the larger orange piece (C1) to C2.
Note that the two pieces lock together to form a final product.


15. In the space below, sketch and label the enzyme and products after the enzyme has acted on the
substrate.

 

Note: A real life example of anabolism occurs when RNA polymerase links RNA nucleotides together
by catalyzing the formation of a bond between the backbone sugar of one nucleotide to the backbone
phosphate of another nucleotide during transcription.

16. Given what you now know about anabolism, identify the substrate in the above diagram.
____________________________________________________________________________________


17. Explain why the above process is an example of anabolism.
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Lock and Key Model of Enzyme Action

In 1894 scientist Emil Fisher wrote, “To use a picture, I would like to say that enzyme and glucoside have to fit to each other like a lock and key in order to exert a chemical effect on each other.” Fisher created a mental model of how an enzyme acts and referred to it as the Lock and Key Model of Enzyme Action.


This model suggests that the enzyme and the substrate possess specific complementary geometric shapes
that fit exactly into one another like a key into a lock.

18. Describe how the anabolic process you previously modeled illustrates the lock and key model of enzyme-substrate interaction.

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Note: Most enzymes catalyze either catabolic OR anabolic processes. There are a few enzymes that do both. ATP synthase and ATPase are the same protein but have different names because they function as enzymes in both catabolic and anabolic reactions.

Diagram A — ATP Synthase Diagram B — ATPase

19. Describe the action of the enzyme in diagram A. In your description, identify the substrate and enzyme.
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Enzyme Specificity

The reaction catalyzed by an enzyme is very specific. Most enzymes are proteins with unique threedimensional configurations based on their amino acid sequence. The specificity of an enzyme can be attributed to the compatibility between the shape of the enzyme’s active site and the shape of the substrate.

Model pieces needed

gray A foam piece
without stickers
green B1 and B2
foam pieces
orange C1 and C2 foam pieces

 

1. Place the enzyme model with the sticker side facing up. Write your observation about the active site of the enzyme below.
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2. What might these specialized areas in the enzyme represent?
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3. What do the red D and tan E foam pieces represent?
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4. How do the specialized areas of the red D piece interact with the specialized areas of the enzyme?
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5. In order for enzymes to bind to the correct substrate, enzymes have specific active site configurations that allow for interaction with the substrate. Explain why the tan E substrate would not interact with the enzyme.
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