The Factors Affecting Enzyme Activity
Laboratory Report by Christopher Ritter
Email: ChristopherRitter@my.unt.edu
BIOL 1730.518
October 10, 2012
Lab Instructor: Bikash Adhikari
Laboratory Day and Time: Wednesdays at 8:00am
Abstract
This report shows the amounts of enzyme activity throughout different tissue extracts, including
apples, potatoes, chicken breasts, and liver. Only a drop of each abstract was used in 4 test tubes
and a dropper of water was added to each of them. Then, to see the enzyme activity in action, a
dropper of hydrogen peroxide was added to each tube. Bubbles and foam began to form as signs
of enzyme activity. Liver was determined to have the highest amount of enzymatic activity with
greatest amount of foam recorded. As for the chicken breast and potato, they each had
significantly less than the amount the liver had. The apple showed no signs of enzyme activity.
Because the liver extract showed more enzymatic activity in the test tube, the liver has more
enzymes than the apple, potato, and chicken breast. Also, animal cells tend to show more signs
of enzyme activity than plant cells.
Introduction
Enzymes are catalysts that speed up chemical reactions. Without them, life could not
exist because chemical reactions would happen so slowly. That is why enzymes are so important
to everyday life. So many exist that not all cells have the same enzymes inside them, making
them all the more interesting and unique.
Enzymes lower the activation energy needed for the reaction to occur. Free energy is
added to the reactants first before the reaction can start, and this energy can be gained faster by
the reactants with enzymes.
The structures of enzymes are in such a way that allows them to fit substrate molecules.
Substrates are simply the molecules that bind with enzymes. With the enzyme and substrate
working together and interacting in order for the substrate to fit into the active site of the
enzyme, a whole new product is made and then the enzyme can transform many other substrates
to products as well(Lippard and Berg, 276). The amount of enzyme activity is depended on how
many enzymes there are in a given location.
Some factors that could affect enzyme activity are tissue extract, temperature, and pH.
For temperature, enzyme activity increases until it gets to 60 degrees Celsius (Royer, 57). Then,
it plummets. As for pH, it’s more complex. It ultimately depends on the stability and structure of
the enzymes (Royer, 55). Whether it is pH or temperature, enzyme activity usually has a broad
range of pH and temperature that really show results. In a liver, the reason it has so much
enzyme activity is because of the abundance of catalase, an enzyme that quickly breaks down
hydrogen peroxide. This kind of reaction produces bubbles and foam when in a test tube. The
amount of enzyme activity is measured as the amount of foam produced after the reaction. In an
experiment involving tissue extracts, different tissues will be used to measure the amount of
catalytic activity they have in their cells.
Materials and Methods
To test the enzyme activity on different tissue, we used four tissues from the following: apple,
potato, chicken breast, and liver. In order for us to test the enzyme activity, we had to make
extracts of these tissues. We used the following procedures in order to produce the tissue extracts
using a spatula, dropper, mortar, and pestle (Note: Do this for each tissue sample):
1. Cut the tissue into small cubes about 0.5cm on a side with a scalpel.
2. In the mortar, add a pinch of sand and a dropper of water. Place the small square tissue
into the mortar as well.
3. Grind the tissue with the pestle.
4. The experiment requires 1 drop of the extract.
5. After the experiment, clean the mortar, pestle, and dropper to avoid contaminated results
that are inaccurate.
Once the extractions of all tissues were finished, it was time to start the real experiment.
Grabbing 4 test tubes, we placed a drop of one of the tissue extract in each test tube and 1
dropper of water to each. Then, we added a dropper of hydrogen peroxide to each tube and
recorded the thickness of the foam created by the reaction in millimeters.
Results
In the experiment, the tissue extract that reacted the most was the liver. The thickness of the
foam was the greatest, so liver had the most enzyme activity. In the apple, no foam was found, so
no enzyme activity was detected. However, the chicken breast and potato had very little activity
as the foam barely rose above up.
Discussion and Conclusion
With these results, our hypothesis that the breakdown of hydrogen peroxide occurs at the
same rate in all cells is proven false. In this experiment alone, we found some cells that didn’t
react at all, reacted very little, or reacted a lot. That is why it is easy to reject the hypothesis. We
were expecting a bit more diversity in the foam length. The apple, potato, and chicken breast had
results so close together that if liver wasn’t tested, the hypothesis may have been or more likely
to be true.
The liver extract results so that a lot of catalytic activity occurs within animals. In food like
apples and potatoes, there were barely any signs of catalytic activity, showing that plant cells
don’t have many catalases. A question that could come up to someone’s mind after the
experiment can be: What type of animal cell has the most catalytic activity?
References
1. Lippard, S.J., J.M. Berg. 1994. Principles of Bioinorganic Chemistry, University Science
Books, Mill Valley, CA.
2. Royer, G.P. 1982. Fundamentals of Enzymology, John & Wiley Sons, Inc., New York, NY.