Download IB Enzyme Lab 2015

IB Biology SL - Enzyme Activity Lab
Performed:
Due:
Closure:
This laboratory involves the use of an enzyme that will react with hydrogen
peroxide. The enzyme is catalase and hydrogen peroxide (H2O2) is the substrate.
The reaction is as follows:
catalase
2H2O2
2H2O
+
O2
Ingested hydrogen peroxide is a poison, while external use of this substance is not.
However, the generation of oxygen gas requires careful handling due to the potential
combustion hazard oxygen presents when handled near a:
a) heat source - open flame b) spark potential - static discharge
Wear safety goggles when pouring hydrogen peroxide.
During this lab all data will be based upon in vitro (outside the organism)
observations as opposed to in vivo (inside the organism). Also, we are assuming
that the amount of gas produced is indicative of enzyme activity.
Figure 1.
Activation Energy - the energy needed to initiate a reaction
Reaction
Activation Energy
no catalyst
(1)
2H2O2
2H20 + O2
EA1 = 72
kcal/mol
2H20 + O2
EA2 = 52
kcal/mol
2H20 + O2
EA3 = 20
kcal/mol
iron (Fe)
(2)
2H2O2
catalase
(3)
2H2O2
1
2
3
EA1
EA2
EA3
- spontaneous
reaction
Activation Energy (EA)
∆G is negative
Hydrogen peroxide is a poisonous by-product of reactions in cells and must
Problem:
broken down quickly into harmless substances.
How does the rate of catalase activity changes over a period of time?
Does the amount of catalase present influence how enzyme activity
changes over time?
Materials:
reaction vessels
rubber stopper with tubing
tweezers
10 ml graduated cylinder
3% hydrogen peroxide
100 ml graduated cylinder
crushed beef liver tissue (containing catalase)
overflow trough
filter paper discs
online stopwatch
safety goggles
Procedure:
1) Set up the overflow trough in the sink and fill it with tap water to a level just
below the overflow mark.
2) Submerge the 100 ml graduated cylinder in the trough and invert it so that all
the air is displaced with water. Leave the inverted graduated cylinder standing
in the trough.
3) Wearing safety goggles, measure exactly 10.0 ml of 3% hydrogen peroxide
and carefully pour it into a horizontally positioned reaction vessel.
4) Using the tweezers, soak one filter paper disks in the prepared solution of
crushed beef liver tissue. The disc should be well saturated but the excess
liquid must be wiped off. Carefully place the soaked disc on the upper
surface of the horizontally positioned reaction vessel. Ensure that the liver
tissue does not come into contact with the hydrogen peroxide at this time. If
bubble are observed, clean the reaction vessel and start again.
5) Place the stopper with rubber tubing onto the reaction vessel so that the
stopper makes an airtight seal. Place the reaction vessel beside the overflow
trough and extend the tubing so that it is placed into the inverted 100 ml
graduated cylinder.
6) Revolve the reaction vessel to allow the hydrogen peroxide to come into
contact with the disc. Accurately measure the volume of O2 gas produced
every 10 seconds for a period of 2 minutes. Be sure that the disc remains in
contact with the hydrogen peroxide throughout the 2 minute period.
7) Empty the contents of the reaction vessel into the waste container and
thoroughly clean the reaction vessel with soap and water.
8) Repeat steps 2-7 four more times with one disc of liver tissue.
9) Repeat steps 2-8 with three discs of liver and again for five discs of liver
NB: Be sure to wash glassware thoroughly between trials.
Using the group data, each individual must clearly illustrate the rate of enzyme
activity during each 10 second interval, through the 2 minute time period, for the 3
different amounts of liver tissue.
You will be evaluated for Analysis, Evaluation and Communication