Problems:

Observe the effect of the concentration of enzyme catalase on the rate of a reaction.

Hypothesis:   Make a  hypothesis in reference as to how varying enzyme concentration will change the
                       rate of reaction.
.
Materials:  (per student group)

100 ml graduated cylinder,  (1) 200 ml flasks or beakers with distilled water
potato catalase enzyme extract, 8 each 100 ml beakers or plastic cups, 200 ml of 1% H2O2,
forceps, paper towels, stirring rod, stop watch or clock for timing,  20 disks punched from filter paper

Procedure:   (reaction rate study)

1.   Together with your partners, prepare your enzyme concentrations in the beakers.

Label the beakers with tape and pen: 20%, 40%, 60%, 80%, and 100%.

Make the appropriate solution dilutions. For example, if you are doing test #1(20%),
measure 4.0 ml of the potato extract using the graduated cylinder and pour into
the beaker. Rinse the graduated cylinder, then add 16.0 ml H2O. Stir well with the stirring rod.

2.  Make the rest of the enzyme solutions in a similar manner.  The table below contains the solution requirements.
 

Test Number	enzyme concentration	ml enzyme from potato extract	ml of water
1	100%	20	0
2	80%	16	4
3	60%	12	8
4	40%	8	12
5	20%	4	16

P.S.   If you are lucky, your instructor may have preprepared these solutions for you!

3.  Get a container of 1% hydrogen peroxide.   This is the substrate for this part of the lab.

4.  Pour 30 ml of the 1% hydrogen peroxide solution into clean beaker/cup.  Label this
      beaker/cup the reaction beaker.

5.  Pick up a filter paper with a clean forceps. Using the forceps, dunk the disk in
     your enzyme extract for FIVE (5) seconds, until the disk is uniformly moistened and
     not beaded with shiny drops of liquid.

6.   Drain the disk on a piece of paper towel for five seconds to remove excess enzyme
      from the disk.

7.   Decide who will watch the stop watch/clock, who will watch the rising disk, and
      who will place the disk in the substrate container with forceps (tweezers).

8.   Using forceps, place the filter disk (containing the enzymes) onto the bottom of the
       reaction beaker containing 1% hydrogen peroxide.  The person watching the disk
       should say "start" for the timer when the disk is on the bottom of the container. Watch
       the filter disk.   When the disk arrives flat on the top of the substrate, the team member
       watching should say "stop" and the timer will record the time it took for the disk to
       rise. Record the time in seconds for each of the three trials.  Be precise in your timing
       and recording.

9.    Repeat the trial three times for each concentration of enzyme and record.. Use
       the same substrate for the three trials.

10.  Throw away the substrate solution after the three trials and measure a new supply
        prior to starting the next series of trials.

11.   Take an average of time in seconds for each trial and record the average.

12.    Plot both the team and the class averages if available on graph paper. The graph or
         graphs should display the concentration of enzyme vs. time of reaction.
         Remember to label your axes and title your graph!

Data: (part one)   This should include your data in a systematic and organized fashion in a data table, as well as the
required graph.

Conclusion Questions:  (part one)

1.  Did your results support or reject your hypothesis? Explain.
2.  Why did you do the experiment in triplicate?
3.  Why is using the average of the class data better than using individual group data?
4.  How could this experiment be improved upon?
5.  List several sources of experimental error in this investigation.
6.  Form a conclusion relating catalase concentration to enzyme reaction speed (or rate as it is related to rate).