Enzyme-Catalyzed Reactions Lab
Name _______________________
Date________ Block_____
Introduction:
In addition to your textbook, below are some web resources that will add more background information about enzymes:
http://ntri.tamuk.edu/cell/enzyme2.html
http://www.worthington-biochem.com/introBiochem/introEnzymes.html
In each individual cell of a human there are many chemical reactions taking place, performing the
necessary functions for being a large, complex, multicellular organism. This is relatively easy to
understand. How do these reactions occur? This is not so easy to understand. Chemical reactions involve
the breaking and reforming of chemical bonds between molecules (substrate(s) of the reaction), which
are transformed into different molecules (product(s) of the reaction). Chemical reactions can occur
spontaneously (without added energy or intervention), and indeed many of the chemical reactions
necessary for life processes are spontaneous. Some reactions are not spontaneous. Metabolic pathways are
processes, which involve many chemical reactions that occur in a specific order.
For example, to get energy out of a molecule of glucose, a series of reactions must take place in a
specific order. If you had to rely on these reactions to take place spontaneously, you would wait a very
long time -- you wouldn't be here! Enzymes catalyze chemical reactions so that they occur in a timely and
sequential manner to produce a product.
Enzymes are biological catalysts. They help to increase the rate of chemical reactions. Enzymes are
most often proteins and their three-dimensional shape is important to their catalytic activity. Because of
their 3-D shape, enzymes are highly specific for the reactions that they catalyze. In other words, they are
specific for the substrates that they will act upon. So any one "function", such as getting energy from a
glucose molecule, actually involves many reactions, each with a specific enzyme. Heat and strong acids
can destroy the shape of the active site and make the enzyme nonfunctional. This is called
denaturization. Inhibitors can also change the shape an enzyme and prevent it from working.
Enzyme activity is influenced by many factors. You will be examining some of the major factors,
which influence the activity of an enzyme called catalase. Catalase is an enzyme, which is found in many
cells, but in highest levels in the liver because the liver often functions to break down toxins present in the
blood. Catalase catalyzes the breakdown of hydrogen peroxide:
2H2O2 ------> 2H20 + O2
Hydrogen Peroxide (H2O2) can form in the body during respiration, and are chemically reactive, which
means that they can chemically modify (and thus render useless) other biological molecules.
Notice that catalase is not changed by the reaction, and that the reaction produces heat. Reactions that produce heat are
called exothermic. Hydrogen peroxide will break down all by itself (spontaneously) at a slow rate. Catalase makes the reaction
thousands of times faster and causes bubbling.
We will measure the reaction rate visually and assign a qualitative value;
0 = no bubbling
1= small bubble formation
2= bubbling fast
3= rapid bubbling/foamimg
All enzymes are proteins with active sites that have a shape that must exactly fit the substrate.
SAFETY
SAFETY
SAFETY
SAFETY
SAFETY
SAFETY
1. Goggles must be worn over eyes at all times during this lab.
2. Aprons must be worn since there is a danger of hot water spills.
2. Liver can carry salmonella and E. coli, which is an infection risk. Hands must be washed
AFTER COMPLETING THIS LAB.
3. Hydrogen peroxide will bleach some colors, and may irritate eyes.
4. Heating increases the risk of glass breakage.
5. Hot plates are hot! Heated test tubes are hot! Use test tube holders.
Part I: Where is Catalase Found?
Hypothesis: If catalase is present, then the reaction _________________________________
IV= ___________________________ DV = ______________________________
Materials: dropper, potato, cracker, liver, sugar, paper, well plate, dropper, forceps, H2O2.
Procedure:
Substance
1. Carefully place a small quantity of each material listed above in a well.
2. Do not cross contaminate material – WIPE OFF FORCEPS
3. Add three drops of H2O2. to each well and record observations.
H2O2
only
(control)
Reaction rate
0 = no bubbling
1= small bubble formation
2= bubbling fast
3= rapid bubbling/foamimg
Conclusion for Part I: (Restate hypothesis, summarize procedure, explain results, accept or reject hypothesis.)
______________________________________________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
______________________________________
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Part II: What Effect Does Heat Have on Enzyme Function?
Hypothesis: If catalase is heated, then the amount of oxygen bubbles will __________________.
IV= ___________________________ DV = ______________________________
Materials: potato, 2 test tubes, hotplate, 2 beakers, water, grad. cylinder, test tube holder, H2O2
Procedure:
1.
2.
3.
4.
5.
6.
7.
8.
9.
Carefully 1 mm cubed size piece of raw potato in each of two test tubes:
LABEL one test tube RAW, label the other test tube COOKED.
Add 4mL of water (use dropper) to each test tube.
Place one test tube in the test tube rack. This is your raw potato.
Place the other test tube in a beaker of simmering water. This is your experimental.
Let this test tube cook in the water for 10 minutes.
Drain the water out of each test tube, being careful not to lose the potato pieces.
a. DO NOT CROSS CONTAMINATE!
Equalize the temperature of both test tubes by placing them in a beaker of cold water together for 3 minutes.
Add 3 mL of H2O2 to each test tube and observe.
Group
Control (raw)
Experimental (cooked)
Reaction rate
Conclusion for Part II: (Restate hypothesis, summarize procedure, explain results, accept or reject hypothesis.)
______________________________________________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
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Part III: Does acid destroy an enzyme’s ability to speed up a chemical reaction?
Hypothesis: If acid is added to catalase, then __________________ (more or fewer) bubbles of O2 will be produced.
IV= ___________________________ DV = ______________________________
Materials: dropper, potato, 2 test tubes, water, grad. cylinder, thermometer, test tube holder, H2O2
Procedure:
1.
2.
3.
4.
5.
6.
Carefully place a 1 mm cubed size piece of raw potato in each of two test tubes.
Add 5 drops of HCl (hydrochloric acid) to one tube (experimental)
Add 5 drops of water to the other test tube. (control)
Swirl both test tubes for 3 minutes.
Add 5 mL of peroxide to each test tube.
Record your observations.
Group
Control (water)
Experimental (HCl)
Reaction rate
Conclusion for Part III: (Restate hypothesis, summarize procedure, explain results, accept or reject hypothesis.)
______________________________________________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
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Part IV: Does a base destroy an enzyme’s ability to speed up a chemical reaction?
Hypothesis: If base is added to catalase, then __________________ (more or fewer) bubbles of O2 will be produced.
IV= ___________________________ DV = ______________________________
Materials: dropper, potato, 2 test tubes, water, grad. cylinder, thermometer, test tube holder, H 2O2
Procedure:
1.
2.
3.
4.
5.
6.
Carefully place a 1 mm cubed size piece of raw potato in each of two test tubes.
Add 5 drops of NaOH (sodium hydroxide) to one tube (experimental)
Add 5 drops of water to the other test tube. (control)
Swirl both test tubes for 3 minutes.
Add 5 mL of peroxide to each test tube.
Record your observations.
Group
Control (water)
Experimental (sodium hydroxide)
Reaction rate
Conclusion for Part III: (Restate hypothesis, summarize procedure, explain results, accept or reject hypothesis.)
______________________________________________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
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Part V: Does an inhibitor destroy an enzyme’s ability to speed up a chemical reaction?
Hypothesis: If an inhibitor is added to catalase, then __________________ (more or fewer) bubbles of O2 will be produced.
IV= ___________________________ DV = ______________________________
Materials: dropper, potato, 2 test tubes, water, grad. cylinder, thermometer, test tube holder, H2O2
Procedure:
1.
2.
3.
4.
5.
6.
Carefully place a 1 mm cubed size piece of raw potato in each of two test tubes.
Add 5 drops of copper sulfate (CuSO4) to one tube (experimental)
Add 5 drops of water to the other test tube. (control)
Swirl both test tubes for 3 minutes.
Add 5 mL of peroxide to each test tube.
Record your observations.
Group
Control (water)
Experimental (copper
sulfate)
Reaction rate
Conclusion for Part III: (Restate hypothesis, summarize procedure, explain results, accept or reject hypothesis.)
______________________________________________________________________________________________________
______________________________________________________________________________________________________
______________________________________________________________________________________________________
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Part VI: Questions
1. Draw a diagram that shows how catalase, H2O2, water, and O2 relate to each other in this lab.
2. Where is the enzyme catalase naturally found?
3. What is the function of catalase in living cells?
4. What happens to an enzyme's ability to catalyze a reaction when they are heated?
5. Describe what happens to the active site of enzymes when they are exposed to high temperatures, strong bases or strong
acids.
6. What effect does HCl (hydrochloric acid) or NaOH (sodium hydroxide) have on catalase enzyme?
7. What is the substrate catalase bonds with?
8. What is hydrogen peroxide changed into when catalase reacts with it?
9. Is catalase changed during the reaction? (why or why not)
10. What happens when an inhibitor is added to an enzyme?
11. Explain why peroxide bubbles when you put it on a cut.