Enzyme Lab Report
Billy Wu P4 CP Bio
I
Purpose:
This lab was conducted to find out the activity of enzyme catalase in
different conditions, for example, different pH.
II
Material:
i.
Five potato cubes of 1 cm^3 (four raw: #1 #2 #3 #4, one boiled: #5)
ii.
Vinegar (acid)
iii.
Hydrogen peroxide
iv.
Ammonia (base)
v.
Six beakers A, B, C, D ,E ,F
vi.
Mortar and pestles
III
Procedure:
i.
Temperature change:
1)
Put the raw potato#1 cube in 50ml of hydrogen peroxide in
beaker A.
2)
Leave the cube for five minutes, observe and record the result.
3)
Put the boiled potato cube#5 in 50ml of hydrogen peroxide in
beaker B.
4)
ii.
Leave the cube for five minutes, observe and record the result.
pH change:
1)
Put the raw potato cube#2 in 20ml of vinegar (acid) in beaker C
and leave it for five minutes.
2)
Put the potato cube#2 into hydrogen peroxide in beaker D and
leave it for five minutes, observe and record the result.
3)
Put the raw potato cube#3 in 20ml of ammonia (base) in beaker
D and leave it for five minutes.
4)
Put the potato cube#3 into hydrogen peroxide in beaker E and
leave it for five minutes, observe and record the result.
iii.
Shape change:
1)
Mash the raw potato cube#4
2)
Put the mashed potato cube#4 into 50ml of hydrogen peroxide in
beaker F.
3)
Leave it in the beaker for five minutes, observe and record the
result.
IV
Data:
Result Table for Enzyme Lab
Treatment of potato
Observation
Raw#1 (in hydrogen peroxide)
A lot of bubbles came out fast.
Boiled#5 (in hydrogen peroxide)
No bubble came out.
Raw#2 (in acid)
No bubble came out.
Raw#3 (in base)
Very few bubbles came out.
A lot of bubbles came out
Raw#4 (mashed in hydrogen peroxide)
violently.
V
Discussion Questions:
i.
Pre-Lab Questions:
1)
Gather Background Information:
a)
Q: Why do we need Enzymes?
A: Enzymes help us speed up the biochemical reactions in
body, so it takes less time to finish the process, such as
breaking down food.
b)
Q: Why is the relationship between an enzyme and its
substrate compared to a lock-and-key?
A: Because it’s just like a lock and its key, a specific kind of
enzyme will only work on specific types of substrates.
c)
Q: Why is it important for our enzymes that we keep our
body’s temperature and pH stable?
A: The unstable temperature and pH can make enzymes lose
their shapes and unable to work with their substrates.
d)
Q: What does the enzyme catalase do?
A: The catalase breaks down H2O2, a harmful product of
certain metabolic reactions, into water and hydrogen gas.
e)
Q: How can we tell if catalase is active (working)?
A: If there are lots of bubbles produced, the reaction speed is
fast and the catalase enzyme is active. Vice versa.
2)
State a problem:
Direction: We will test them one at a time, because in a controlled
experiment you never want to change more than one thing at a
time.
f)
How does changing the temperature of a potato affect the
activity of catalase?
g)
How does changing the pH of a potato affect the activity of
catalase?
h)
3)
How does mashing the potato affect the activity of catalase?
Hypothesize:
i)
If I boil my potato then the activity of catalase will decrease
because the heat will break up the bonds of protein.
j)
If I put my potato in vinegar (an acid) then the activity of
catalase will decrease because enzymes will be denatured
when there is any change in pH.
k)
If I put my potato in ammonia (a base) then the activity of
catalase will decrease because enzymes will be denatured
when there is any change in pH.
l)
If I mash up my potato then the activity of catalase will stay
the same because the enzyme is actually not affected, it’s just
the physical change of the shape of the potato.
ii.
Analyze Results:
4)
The important part
In this experiment
Independent variable
Different potato treatments
Dependent variable
Bubbles different potato cubes produced
Experimental group(s)
Raw#2, Raw#3, Raw#4, Boiled#5
Control group
Raw#1
1. The origin of potato cubes
2. The size of potato cubes
Constants
3. The origin of hydrogen peroxide
4. The amount of hydrogen peroxide
5)
Q: How did increasing the temperature of the potato affect the
activity of catalase?
A: The increasing temperature lowered the activity of the catalase,
as the high temperature broke down bonds in proteins of enzyme
catalase.
6)
Q: How did changing the pH of the potato affect the activity of
catalase?
A: The change in pH lowered the activity of catalase, as every
enzyme catalase had an interval of pH of the best activity, and
once the pH was out of that interval, the activity would be
affected negatively.
7)
Q: In which potato was catalase the most actively? Why do you
think this was?
A: The mashed potato cube#4 released the most bubbles in
hydrogen peroxide and the speed was the fastest, because the
mashed potato cube had a larger surface area to hydrogen
peroxide, so more enzyme catalase was active.
iii.
Post-Lab Questions:
8)
Q: Why is the relationship between an enzyme and its substrate
compared to a lock and key?
A: Because an enzyme only works perfectly on its substrate, just
like a key only opens a specific lock.
9)
Q: Changing in temperature or pH can change an enzyme’s shape.
Why will an enzyme no longer work if it loses its shape?
A: Once an enzyme loses its shape, known as being denatured, the
enzyme doesn’t fit its specific substrate anymore, so it will no
longer work.
10) Q: What is the optimum pH of enzyme X?
A: pH of 8 is the optimum pH of enzyme X.
11) Q: What is the optimum temperature of enzyme X?
A: 20°C is the optimum temperature of enzyme X.
12) Q: Why do you think enzyme X has low activity at a pH of 10?
A: Because it comes to a base when the pH is 10, and base will
break bonds of proteins in enzymes, which lowers the activity of
enzyme X.
13) Q: Enzyme X performs critical life functions. Use the data above to
explain why a fever of 40 degrees may be dangerous.
A: The optimum temperature for enzyme X is 20°C, and when it
comes to 40°C it totally stops working. Since enzyme X is a critical
life functions, when one has a fever of 40°C the enzyme loses its
functions, so this person probably will die because of lacking that
critical life function enzyme X brings.
VI
Conclusion:
This lab was conducted to find out the activity of enzyme catalase in
different conditions: different pH, different temperature and different
surface area. In the experiment, control groups were set for comparing
how changing environments could affect the activity of enzyme catalase. As
a result, it showed that the change in pH and temperature affected the
activity of enzyme catalase negatively, and the increasing surface area
affected the activity positively. The explanation for the result is that, high
temperature would break the bonds in proteins of the enzyme, and the
changing pH would denature the enzyme, which both lowered the activity;
however, the increasing surface area increased the activity of enzyme
catalase because more enzyme is in reaction with hydrogen peroxide.
VII Source of Errors:
1. Potato
2. Quality of ammonia, vinegar, and hydrogen peroxide
3. Quantity of ammonia, vinegar, and hydrogen peroxide