ENZYME
LAB PRESENTATION
By May, Nam T., Por, Parn, Mook, Mix (10-9)
Objective
To study how pH, temperature, ionic
conditions, substrate concentration
affects enzyme activity
Something you should know before :
- The enzyme that is used in this experiment is ‘ urease ’, which
contains in the soya bean.
- Soya suspension, in this experiment, is used as an enzyme for
urea.
- The substrate is the urea.
- Enzyme urease breaks down urea to ammonia and carbon
dioxide.
CO(NH2)2 + H2O  2 NH3 + CO2
Urea
+
water

ammonia +
carbon dioxide
Something you should know before (cont.)
:
- Ammonia that is produced has a high pH (basic).
- We can detect ammonia by using the red cabbage indicator
and also by smelling.
Procedure 1: Investigation of urease
enzyme and Indicator
Hypothesis
-
Drop citric acid  change to red
Drop sodium bicarbonate  change to blue
Drop distilled water  no change
Result
Test tube 1Citric Acid
Test tube 2Sodium
Carbonate
Test tube 3Distilled
Water
Color (initial)
Purple
Purple
Purple
Color (final)
Red
Dark greenish
blue
Purple
Answer questions
1. Why is it important to have three reference tubes?
Each reference tube contains acid, base and distilled water,
which is neutral, respectively. They are a control for reaction
between red cabbage indicator and acid, red cabbage indicator
and base, and the same indicator and water. They show the
different results after the indicator reacts with acid and base.
2. Can you predict what color of the solution will
be if the urease enzyme converts urea to
ammonia?
I can predict that the color of the solution will be
blue or green, as the result, when red cabbage indicator
reacted with sodium carbonate, which is basic, it became
blue or green.
Procedure 2: Investigating the effect
of urease from soya beans on urea.
Hypothesis
-
The test tube which contains both urease and urea will be
the only one test tube that changes the color.
Result
Test tube 1Urea
Test tube 2Urea + Soya
Test tube 3Distilled
water + soya
Color change
Purple
Green
Light purple
Odor(smell)
No smell
Light smell
Strong smell
Answer the questions
1. What are the purposes of procedure 2? (Think about
the total contents in each tube, and what can the results
from each tube tell us.)
The purpose of procedure 2 is to test the enzymatic
working, which shows that if there is only the enzyme (only
urease) or only the substrate (only urea), the enzymatic reaction
cannot occur. The reaction will occur when there are both the
enzyme and the substrate fitting each other such that the test tube
2 represents.
2. Why do we need to add an enzyme into a test tube
without urea even though we can predict that no enzyme
activity can occur?
Because we want to make sure that we can use this
indicator to test the pH changing. If we add the enzyme into the
test tube without urea (test tube 3) but the color changes then we
cannot use this indicator to test in this experiment. Although we
can predict that no enzyme activity can occur but we have to
double-check the result.
Procedure 5: Effect of the concentration
on urease
Hypothesis
-
The color of the solution of both test tube with 5% NaCl and
with 10% NaCl will change to green.
Result
Test tube 15% NaCl
Test tube 210% NaCl
Test tube 3Saturated
NaCl
Color change
Clear green
Clear greenish Opaque blue
blue
Odor(smell)
Light pungent
Light pungent
A bit strong
pungent
Answer the questions
1. How does ionic condition affect the urease
activity? How do you know?
The ionic condition affects the rate of the urease
activity. The rate of the activity depends on the ionic
concentration; if the concentration of the ionic substances
increases, the rate will increase. However, too much
concentration can stop the reaction as well that means the
enzyme will not cause the reaction anymore. We can know
that from the color of the solutions from the results. When
the activity occured, the color of the solution turned green.
If the solution is blue, the activity did not occur.
2. From your results, what ionic condition would you
use and avoid if you have to conduct an experiment
using urease enzyme and why?
We would use the 5% NaCl ionic condition and avoid
the saturated NaCl ionic condition, because, according to
the experiment, the 5% NaCl ionic condition could use the
most efficiently, it could cause the faster activity; whereas
the more than 5% NaCl can lower the rate of the activity.
Moreover, the saturated can stop the activity because of the
too much concentration of the ionic substances, NaCl.
3.Your special task is to try and deactivate the
enzyme with table salt.
We can deactivate the enzyme by adding a lot of salt.
Much concentration of the salt can deactivate it.
What were you able to learn from this
experiment?
- Temperature, pH, ionic condition, substrate
concentration are all the factors that affect
enzymatic reaction.
- Enzyme can work in only its properly condition.
- Two ways to detect the reaction; indicator and smell
- Red cabbage indicator can be used to detect
ammonia.
What were you able to learn from this
experiment? (cont.)
- Urease is an enzyme of urea that can be found in
soya beans, as in the experiment, the enzyme activity
causes when we added soya.
- When urease breakdowns urea, ammonia and carbon
dioxide are the products.
- How to work in group
Did your results support the prediction
made before conducting the experiment. If
it did not, then explain why.
=> All the results have supported our prediction or
hypotheses.
Any experimental errors? How can you
avoid these errors in the future?
The contaminated urea
 Do not suck the chemical directly from the bottle
 Do not pour the rest chemical back into the
bottle
 Keep the chemical correctly, close the lid tightly
 Check the chemical before starting the
experiment
Thank you for your
participation 