Investigating The Action of Peroxidase
Name:
________________________________ Period______
Observation:
Enzymes speed up chemical reactions.
Questions:
a) How does peroxidase effect hydrogen peroxide?
b) Is peroxidase reusable?
c) Will peroxidase react with substances other than hydrogen peroxide?
Research:
In this lab, you will study an enzyme that is found in the cells of many living tissues
(including chicken liver!). The name of the enzyme is peroxidase; it speeds up a
reaction that breaks down hydrogen peroxide into water and oxygen. This reaction is
important to cells because hydrogen peroxide (H2O2) is toxic but is produced as a
byproduct of many normal cellular reactions. If cells did not break down the hydrogen
peroxide, they would be poisoned and die.
a) What is the name of the enzyme in chicken liver? ______________________________________
b)
In general, what is the job of an enzyme?
______________________________________
_______________________________________________________________________________
c)
What is the chemical formula for hydrogen peroxide?
______________________________________
d)
What does this specific enzyme (peroxidase) do? ______________________________________
_______________________________________________________________________________
e) Why is this enzyme important to have in our body?
__________________________________________________________________________
f) Write the chemical equation for the reaction of peroxidase and hydrogen peroxide.
(enzyme name)
_____________________
>>>----------->>>
__________
+ ___________
A.
If hydrogen peroxide (IV) is mixed with peroxidase enzyme, the
products will be water (DV) and oxygen gas (DV).
B.
If peroxidase enzyme (IV) has been used before, then it can be
used again to convert hydrogen peroxide to water (DV) and oxygen
gas (DV). OR If peroxidase enzyme (IV) has NOT been used before,
then it can be used again to convert hydrogen peroxide to water (DV)
and oxygen gas (DV).
C. If peroxidase reacts with other substrates other than hydrogen
peroxide, than water and oxygen gas will still be formed (fizzing).
OR If peroxidase does not react with other substrates than
hydrogen peroxide, than water and oxygen gas will not be formed (no
fizzing)
Materials:
3% hydrogen peroxide
fresh liver
test tubes
test-tube holder
alcohol
straw
Methods:
PART A – THE BASIC ACTION OF PEROXIDASE
1. Pour about 1 cm of hydrogen peroxide into a clean test tube.
2. Using forceps and scissors cut off a SMALL (pea-sized) piece of liver and add it to the
test tube.
3. Record ALL observations in results section A. Observe for at least 5 minutes. Describe
what is happening in your test tube.
4. When the reaction is COMPLETELY finished, move onto part B. While you are waiting,
do part C.
PART B – ARE ENZYMES REUSABLE?
5. Pour off the liquid into another test tube marked 2. Leave the liver in test tube 1.
6. Add another SMALL (pea-sized) piece of liver to tube 2. Record results section 2.
7. Add about 1 cm of hydrogen peroxide to the liver remaining in test tube 1. Describe
what you observe in results section 2.
8. Clean both test tubes well.
PART C – CAN PEROXIDASE REACT WITH OTHER SUBSTANCES?
9. Carbon dioxide is also produced as a result of cellular reactions. Obtain a test tube and
fill it with 1 cm of water.
10. Blow through a straw into the water for 30 seconds to accumulate carbon dioxide.
11. Add a small piece of liver to see if the liver will react to the carbon dioxide and record
your results in results section C.
12. Then, in a clean test tube, combine alcohol and liver. Does peroxidase react with
alcohol? Record your results.
13. Before leaving the lab, clean up all your materials, clean test tubes, wipe area and wash
hands thoroughly!!! Failure to complete this part will result in lost points!!
Results:
A
B
C
TUBE 1
(OLD liver, NEW hydrogen peroxide)
TUBE 2
(NEW liver, OLD hydrogen peroxide)
INDIVIDUAL Analysis Questions:
 For this lab we will be answering analysis questions INSTEAD of writing a
discussion.
 Answer using COMPLETE sentences when applicable. EXPLAIN your results
CONCISELY!
 Please do not use personal pronouns (I, you, we, our group) in your answers.
 Complete these by yourself!!!!
1.
What was the overall purpose of this lab – parts A, B and C?
________________________________________________________________
__________________________________________
2.
What was the enzyme used in this lab?
________________________________________________
3.
What was the source of the enzyme?
________________________________________________________
4.
What was the substrate?
_______________________________________________________________
5.
What was the purpose for part A?
________________________________________________________
________________________________________________________________
6.
Answer question A. Support with observations. Then, state and analyze your
hypothesis for part A. Was it correct or not? Explain.
________________________________________________________
________________________________________________________________
7.
What gas is released in part A?
_______________________________________________________________
8.
What was the liquid left after the reaction in part A?
_____________________________________________________________
9.
What was the purpose for part B?
______________________________________________________________
________________________________________________________________
Answer the question for part B and then analyze your hypothesis for part B. Was it
correct? Why or why not? Incorporate your observations.
________________________________________________________________
____________________________________________________________________
____________________________________________________________________
___________________________________________________________________
Explain why there was no reaction in tube 1 with the NEW liver and the OLD hydrogen
peroxide.
_______________________________________________________________
____________________________________________________________________
_________________________________________________________________
10.
What was the purpose for part C?
_________________________________________________________
________________________________________________________________
Answer question C and then analyze your hypothesis for part C. Was it correct? Why
or why not? Incorporate results.
11.
Name and define the TERM that describes what is happening in part C.
________________________________________________________________
____________________________________________________________________
____________________________________________________________________