Research Question:
What effect do temperature and pH have on the activity of the enzyme peroxidase?
Background:
Peroxidase is an enzyme in the potato which removes destructive peroxides that are a product of normal metabolism. The enzyme catalase performs this function in almost all animals. Hydrogen peroxide is highly poisonous to cells. Peroxidase speeds up the chemical breakdown of hydrogen peroxide into water and oxygen. The equation for this reaction is written below:
2 H
2
O
2
(aq)  2 H
2
O (l) + O
2
(g)
Hypotheses:
Materials:
Petri dish, tweezers, scalpel, potato pieces, base solution, acid solution, hydrogen peroxide
Procedure:
1.
Cut a 5mm thick slice off a fresh potato.
2.
Divide the potato into three sections for testing three conditions.
3.
Scratch the surface of the potato pieces with tweezers to create a rough surface and open up the cells.
4.
Cover one section with acid using the dropper/pipette.
5.
Cover another section with the base using the dropper/pipette.
6.
Obtain one frozen piece of potato and one boiled piece of potato.
7.
Scratch the surface of the frozen and boiled pieces of potato.
8.
Place the five sections of potato in petri dishes.
9.
Drop hydrogen peroxide onto the untreated potato section and observe the reaction.
10.
Repeat step #9 for each of the remaining 4 pieces of treated potato.
11.
Record all results in the table provided using the following terms to rate the reaction: none slow moderate fast
Data Table:
POTATO SAMPLE
Room temperature/untreated
Acid treated
Base treated
Frozen
Boiled
RATE OF REACTION

Analysis Questions:
1.
What are enzymes in general and what do they do?
2.
Which enzyme was tested in this activity and what is its function?
3.
What enzyme performs the same function in humans?
4.
What was the control in this experiment?
5.
What happened when the hydrogen peroxide was added to the potato?
6.
What chemical reaction occurred?
7.
What were the reactants and products in this reaction?
8.
What is a substrate in general and in this experiment?
9.
What were the independent variables in this experiment?
10.
What was the dependent variable in this experiment?
11.
Which condition(s) showed less reaction than the control? Why?
12.
Which condition(s) showed no reaction? Why?
13.
Which condition(s) showed the greatest amount of activity? Why?
14.
What are the best conditions for peroxidase to work in?
Conclusion:
What did you learn by doing this experiment? Was your hypothesis supported or rejected by your data?
Provide evidence. How does this experiment relate to the “real world?” Provide a concrete, well explained example. Where would you go from here? What needs to be further investigated based on your results and conclusions?