Download Effect of Temp on Enzyme Activity Pre-Lab

Name_________________________
Biology
Date___________
Band ___________
Background Reading: Read the following background info and answer the questions as
the Pre-Lab for our Enzyme Lab
http://academic.brooklyn.cuny.edu/biology/bio4fv/page/enz_act.htm
Effect of temperature on enzyme
activity
1. What is Kinetic Energy? ___________________________________________
The temperature of a system is to some extent a measure of the kinetic energy of the
molecules in the system.
Thus, lower the temperature of the system, the lower the kinetic energy is.
Likewise, the greater the temperature of the system, the higher the kinetic energy is.
Increases in the temperature of a system results from increases in the kinetic energy
of the system (meaning the molecules move around more)
1) More energetic collisions between Molecules
When molecules collide, the kinetic energy of the molecules can be great enough to reach
the activation energy of an exergonic reaction, thereby triggering the reaction. Thus, as
the temperature of a system is increased it is possible that more molecules (per unit time)
will reach the activation energy. Thus the rate of the reaction may increase.
2) The number of collisions per unit time will increase.
In order to convert substrate into product, enzymes must collide with and bind to the
substrate at the active site. Increasing the temperature of a system will increase the
number of collisions of enzyme and substrate per unit time. Thus, the rate of the reaction
will increase.
3) The heat of the molecules will increase.
As the temperature of the system is increased, the molecules will become hotter. Some of
this heat may be great enough to break the weak hydrogen bonds that determine the three
dimensional shape of the active proteins. This could lead to a denaturation of the protein
and thus inactivate the protein. Thus too much heat can cause the rate of an enzyme
catalyzed reaction to decrease because the enzyme or substrate becomes denatured and
inactive.
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2.
In what ways can temperature Increase the Rate of an enzyme Reaction?
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3.
In what ways can temperature Decrease the Rate of an enzyme Reaction?
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Optimal Temperature of an Enzyme
Each enzyme has a temperature range in which a maximal rate of reaction is
achieved. This maximum is known as the optimal temperature of the enzyme.
In the above figure the Optimal Temperature of three different enzymes is depicted. You
should note that the Optimal Temperature of each enzyme is different.
The Curve in blue (farthest left) might represent an enzyme isolated from a shrimp that
normally lives in the cold waters of Alaska. Thus its enzymes have evolved to work best
at lower temperatures.
The curve in red (middle) might represent an enzyme working at body temperature.
The curve in green (far right) might represent the temperature optimum obtained with
an enzyme isolated from a bacterium that normally lives in the hot springs of
Yellowstone National Park. The enzymes from this bacterium would work best at
temperatures that would normally denature enzymes isolated from you or me.
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4. Why would different enzymes have different Temperature Ranges with different
Optimal temperatures?
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OUR Enzyme Lab
Objective:
To Determine the Temperature range, estimating the Optimal temperature, of Catalase.
Introduction:
In this lab, we will use a simple reaction (H2O2  H2O +O2) to determine the
temperature range and Optimal temperature of the enzyme Catalase.
Hypothesis:
How do we think temp will affect the rate of catalase? What do we think the optimal
temp for catalase will be? Why? _____________________________________________
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Materials
o Filter paper circles (hole punch)—many
o Hydrogen Peroxide
o Diluted Catalase (Liver puree) at various Temperatures:
 #1 Room Temp
 #2 Warmer (100 Degrees Celsius?)
 #3 Colder (0 Degrees Celsius?)
o Forceps (tweezers)
o Paper towels
o 2 beakers (1 small, 1 medium)
o Stop Watch
o Ice Bucket
o Hot Plate
Procedure:
 First we must dilute the concentration of Catalase so that the reaction is slow
enough to be timed. I will tell you what concentration to mix.
 Pour ____________ml of Hydrogen Peroxide into the medium beaker
 Pour about 10 ml of Catalase (Temperature #1: Room Temp) into the small
beaker.
 Take a small filter paper disk (make sure to use one at a time—sometimes they
stick together, so use your nails to pull them apart) and using the tweezers, dip it
into the enzyme beaker, saturating it. Dab any excess liquid off onto a paper
towel. Dry the tweezers before the next step. **IMPORTANT**
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 Using the tweezers, carefully place the disk at the bottom of the medium beaker
of Hydrogen Peroxide, by pressing it to the bottom of the beaker for a moment.
Then when you let go, start the stopwatch and time how long it takes for the disk
to reach to surface. Remove disks from the surface before doing the next trial.
 Repeat this for 3 trials at each Temperature and Record the Average of the 3 as
your Reaction Time in seconds.
 Continue this procedure for the enzyme at all the various temperatures. Also
Include a Control Trial
-----------------------------------------------------------------------------------------------------------5.
Why is it important to Dab the excess liquid off the filter paper before placing it
into the beaker of Hydrogen Peroxide? How could forgetting to do this affect our
results?___________________________________________________________
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6.
Why do we do 3 trials for each enzyme temperature?_______________________
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7.
What is causing the Filter disk to rise to the surface?
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8.
How do you know that the filter disk is rising because of the enzyme reaction?
What control could you conduct to determine this?
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Results:
For Homework:
Construct a DATA Table in your Lab Notebook to record your results in. Remember that
each Temperature will have 3 trials and then be averaged. How many temperatures
should we test to get a good picture of the full range of the enzyme? Leave plenty of
empty spaces to add temperatures as we go
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After recording the time each reaction took at each temperature, Graph your results to
determine the Temperature range and Optimal Temperature of Catalase.
The Graph should be a line graph of Reaction Time Over Temperature.
Once you’ve answered all the questions here and constructed your data table—you are
ready to begin!
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