INQUIRY LAB: ENZYMES
Scientists __________________________________ Date __________ Block __________
Background Information:
Enzymes are important in living organisms. They speed up chemical reactions. Without enzymes, we would
not be alive. Their function is determined by their shape, so they are highly specific – they will work only
with one set of reactants. If their shape gets changed (unfolds or denatures), they can’t work. Some
environmental factors might change the shape of the enzymes and make them non-functional.
A basic enzymatic and substrate reaction can be depicted as follows:
Enzyme + Substrate → Enzyme-Substrate Complex → Enzyme + Products + ∆ G
Two common types of enzymes are (1) catabolic enzymes that break things down (like lactase breaks down
lactose) and (2) anabolic enzymes that build up. (You may know this second word already from stories
about athletes who have been caught using illegal anabolic steroids to build muscle.)
Catalytic enzymes, called proteases, break down proteins and are found in many organisms; one example is
bromelain, which comes from pineapple and is an ingredient in commercial meat marinades. Papain is an
enzyme that comes from papaya and is used in some teeth whiteners to break down the bacterial film on
teeth. People who are lactose intolerant cannot digest milk sugar (lactose); however, they can take
supplements containing lactase, the enzyme they are missing. All of these enzymes hydrolyze large,
complex molecules into their simpler components; bromelain and papain break proteins down to amino
acids, while lactase breaks lactose down to simpler sugars. Anabolic enzymes build larger molecules, such
as combining amino acids to make proteins.
In this investigation, you will focus on the enzyme peroxidase found in cells of many organisms (this
peroxidase is from a turnip). Peroxidase is one of several enzymes that break down peroxide, a toxic
metabolic waste product of aerobic respiration. Using peroxidase, you will develop essential skills to
examine your own questions about enzyme function. You will use hydrogen peroxide (H2O2) as a substrate.
A peroxidase in your cells is what makes hydrogen peroxide bubble if poured on a cut. Like all enzymes the
peroxidase is not used up during the reaction. The reaction is:
Peroxidase + Hydrogen Peroxide  Peroxidase + Water + Oxygen
2H2O2 → 2H2O + O2 (gas)
In the second part of this investigation you will have an opportunity to design and experiment to test the
effect of one environmental factor on the rate of this chemical reaction.
Prelab: Answer the following review questions in complete sentences.
1. What is the purpose of enzymes in a biological system?
2. How does shape of the active site affect the function of the enzyme?
3. What is the function of peroxidase in a cell?
4. How will the following affect the rate of an enzymatic reaction?
(a) increase in the amount of substrate
(b) increase in the amount of enzyme
(c) increased concentration of products
5. What are two environmental factors that affect enzyme function?
active site 
6. What causes denaturation of a protein?
7. How does denaturation affect the structure and function of an enzyme?
Part 1: Showing the effect of an enzyme on the rate of a chemical reaction.
We will be using the reaction : 2H2O2 → 2H2O + O2 (gas). To see how fast the reaction occurs, we will
measure how much oxygen (O2) is produced. This could be done by measuring the actual volume of oxygen
gas released or by using an indicator. In this experiment, an indicator for oxygen will be used. The
compound, guaiacol, has a high affinity for oxygen, and in solution, it binds instantly with oxygen to form
tetraguaiacol, which is brownish in color. The more oxygen gas produced the darker brown the
solution will become.
To get a measure of the color, we’ll use a color chart ranging from 1 to 10 (available at each lab
station) is sufficient to compare relative amounts of oxygen produced.
Step 1 Using tape and a marker label the test tubes A and B.
Step 2 Using the syringes Add solutions to test tubes A and B as indicated in the table below.
tube label
A
B
solution to add
7.5 mL of diluted H2O2 (substrate or reactant)
0.2 mL of guaiacol (color indicator) – located in the hood
7.5 mL enzyme
Step 3 Pour the contents of test tube A into test tube B. Pour back and forth twice to mix, then
immediately begin timing the reaction. Compare the color of the solution in the test tube to the color
chart at your lab station, and record the color at time zero.
Step 4 Observe the color change for the next 5 minutes and record the observed color at 0, 1, 2, 3, 4,
and 5 minutes in the ‘with enzyme’ column. The reaction without enzyme will be done as a demonstration.
Minutes
0
1
2
3
4
5
Color of solution (1-10)
Without enzyme
With enzyme
GRAPH 1: compare reaction rate by graphing the color of solution (y axis) vs the time (x axis)be sure to include all items needed for a graph (DRY, MIX, TALK)
Analysis questions for Part 1.
1. How does the color change indicate that the reaction is occurring? (Refer to the information at
the top of this page and be specific.)
2. What is the effect of the enzyme peroxidase on the rate of reaction?
Part 2: What are the effects of environmental factors on the rate of reaction?
A. Model: What things affect a chemical reaction? Create a mind map or model of the things that can affect
the rate of reaction. Don’t forget enzymes and the things that affect enzyme shape and function. Indicate if
they will increase or decrease the rate.
B. Design an investigation: Select a variable from your model above that you would like to investigate and
write a Research Question. You will be using the same reaction and basic directions.
RESEARCH QUESTION
C. After you get approval from the teacher, write the hypotheses:
Null hypothesis (factor will not change rate):
Alternative hypothesis (factor will increase or decrease rate and why):
Get approval again before going on.
EXPERIMENTAL DESIGN
INDEPENDENT VARIABLE: ___________________________________
Experimental groups: (be specific; give actual temperature or pH – include all 5 of the groups)
_________________________________________________________________
Control group: (choose one of the experimental groups for the control) ____________________________
DEPENDENT VARIABLE: (what is measured, how) _________________________________________________
CONSTANTS: (refer to the model) ______________________________________________________________
PROCEDURES
(Use the basic directions for Part 1. Number the steps, label first, say what and how much of each
solution, record the color of the reaction at 4 minutes only.)
DATA TABLES (proper data tables)
Group raw data table for your lab group
Class average data table
pH
or 0C
color
GRAPH 2: compare the Effect of the IV on the DV, by graphing the color indicator (y axis)
vs pH or temp ( x axis). (this is a graph of your groups data, NOT the class data; include all necessary
labels)
RESULTS
Restate the hypothesis (The hypothesis was “...”), state the class means in words and numbers, summarize the class
means, and state if hypothesis was supported or not supported.
TABLES AND GRAPHS
On a separate sheet of paper include a typed table of the class average from Part 2 (either pH or temperature
depending on your group’s variable).
On a separate sheet of paper include a typed graph done in EXCEL of the class averages from Part 2 (either pH
or temperature, depending on your group’s variable)
*** be sure to include Title (in all CAPS), table and axis labels, proper scales, ,
Conclusion
Restate the hypothesis (The hypothesis was “...”), summarize the class means, and state if hypothesis was supported or
not supported. Add three references to the conclusions to support your findings.
ERROR ANALYSIS
Error analysis discusses what went wrong (NOT everything that could have possibly gone wrong!). Look at the data.
Does something not make sense? What might have caused that? Was some factor not held constant? How would that
have affected the data?
FUTURE RESEARCH
Future research looks at the ‘next question.’ What other experiment could be done to learn more about
enzymes?
REFERENCES
At least 3 references that are cited in the conclusion section and in proper APA FORMAT
This paper is needed for the PEER Review to be done in class on _________________________.
Turn in this portion of the lab (with the PEER Review comments) and the Results and Conclusions formal
lab.
For the lab write up – you will be completing a separate results and conclusions section based on the class
average data. You will need 3 references used as in paper citations in your final conclusions section.
Follow the instructions and rubric for this lab.