Affecting Enzyme ActivityIan Chachana, Emilie Rose, and Allison
Hocking Purpose: To test the reactivity of peroxidase in extreme
temperatures or pH. Hypothesis: The peroxidase will react faster in
higher temperatures and slower in lower temperatures. It will not
react in extreme pH. Procedure: - Cut potato into 5, 3.5g pieces
and placed two in beakers of water, two in empty test tubes, and
one in a empty petri dish. - Placed one of the beakers full of
water on a hot plate and heated to 650 C, the other beaker had ice
cubes placed in it with the potato and was chilled to 50 C. - Put 5
mL of 0.1 mol/L hydrochloric acid in a test tube with a piece of
potato, and put 5 mL of 0.1 mol/L sodium hydroxide in the other
test tube. - Waited for 5 minutes and removed the pieces of potato
from their acid, base, heated water, or ice water and put them in
separate petri dishes. - Poured 3 mL of 3% hydrogen peroxide on
each potato and recorded the results of the experiment.
Results:Change to PotatoHot Cold Acid Base Neutral
Amount of OxygenVery little None None None Very little
BubblesTwo One None None Many (50-75)
Unreacted PeroxideMost of it All of it All All 3/4 of it
The only one of the modified potatoes reacted with the hydrogen
peroxide and that was the heated potato. The potato produced much
less bubbles and oxygen then the unmodified potato but still
reacted however slightly. The hydrogen peroxide decomposed the
potato however. The edges became transparent and small pieces broke
off. I believe this is because the potato was in water that was too
hot for too long and this caused the proteins holding the potato to
denature. When the hydrogen peroxide was poured onto the potato it
damaged the molecules inside the cells and caused small parts to
detach from it.
Analyze: 1. These laboratory procedures indicate that peroxidase
does not react with under extreme pH or low temperatures.
Peroxidase will not react as strongly in high temperatures because
the heat destroys the cell functions and the hydrogen peroxide
destroys the cell before the reaction can take place. 2. I believe
if the temperature was lower then the reaction would have worked
faster than the unmodified potato because the potato would not have
broken down and the reaction could have worked. 3. HCl reacted with
the peroxidase because the peroxidase is made to keep the cells
safe and the HCl is dangerous to the cell in that concentration.
The peroxidase reacted with the HCl and could not react with the
H2O2. 4. I believe that just like the HCl, the NaOH reacted with
the peroxidase and prevented the expected reaction from happening.
Conclude and Apply: 5. My data rejects part of my hypothesis and
supports an other part of it. I stated that the peroxidase would
not react in extreme pH values or low temperatures and it would
react faster in high temperatures. The peroxidase did not react in
the extreme pH or cold like I expected but it did not react as
quickly in the high temperature as I hypothesized. If done over I
would heat to a lower temperature to achieve a faster reaction. 6.
The peroxidase reacted best at room temperature in a neutral pH,
although it should have reacted faster in the high temperature but
I heated it too high and the reaction failed. 7. The purpose of
control samples was to measure the different reactions without
having a variable from an external source. It lowered the margin of
error so that only one variable was being altered one each piece of
potato so the results could be measured accurately. 8. Hydrogen
peroxide foams when it touches an open wound because our bodies
have peroxidase in them. When we are injured the blood flow to that
area is increased and it carries peroxidase in the blood to protect
the tissues that have been injured from infection. When hydrogen
peroxide is applied it reacts with the peroxidase.
