TESTING ENZYMES LAB
BACKGROUND INFO:
Chemical reactions within cells are catalyzed by a special class of
proteins known as enzymes. Enzymes catalyze (increase) the rate of
specific reactions by reducing the amount of energy needed to get the
chemical reaction started, or the activation energy. The activity of these
enzymes is dependent upon several factors, including the SHAPE of the
molecule, concentration of the enzyme and substrate, pH, temperature,
and presence or absence of other chemicals. Enzyme activity can be
influenced by changing any of these factors. In this laboratory exercise
you will conduct a controlled experiment to determine the influence of
pH on the enzyme catalase. You will also analyze graphs to determine
the effect of temperature on enzyme activity, and design an experiment
to test conditions involved in lactose digestion.
DEMONSTRATION:
Watch what happens a small piece of raw liver is added to a small
amount of hydrogen peroxide.
PROCEDURES:
1. Obtain 5 equal sized beakers. Number the beakers from 1 to 5.
2. The goal is to create five different solutions that have approximately
equal amounts of fluid and a range of pH from very acidic to very
basic. You want the volume of liquids to be the same for each
beaker!
3. Add 5mL of water to beakers 1, 2, 3 and 4.
4. In beaker 1 add enough hydrochloric acid (HCl) to bring the pH to 1
or 2.
5. In beaker 2 add enough HCl to bring the pH to 4 or 5.
6. In beaker 3 add enough sodium hydroxide (NaOH) to bring the pH
to 9 or 10.
7. In beaker 4 add enough NaOH to bring the pH to 13 or 14.
8. In beaker 5 add water until it reaches the same volume as the other
beakers. Water is neutral and will serve as a pH of 7.
9. Add 5mL of hydrogen peroxide to each beaker. THERE SHOULD BE
NO BUBBLING. IF BUBBLING OCCURS YOU NEED TO START OVER WITH
A CLEAN BEAKER.
10. Check the pH of each beaker again to see if the hydrogen
peroxide had any influence. THIS STEP SERVES AS THE CONTROL FOR
YOUR EXPERIMENT. THE SOLUTIONS SHOULD HAVE A RANGE OF pH
AND THERE SHOULD BE NO BUBBLING IN ANY OF THE BEAKERS.
11. Complete the control side of the data table. Score the amount of
bubbling on a scale of 0-3. Zero means no bubbling. 3 means the
greatest bubbling.
12. Using a clean medicine dropper, add 5 drops of catalase (liver
puree) to each beaker and mix well by swirling the beaker. BE SURE
TO ADD EQUAL AMOUNTS OF PUREE TO EACH BEAKER.
13. Observe the results and complete the experimental side of the data
table.
14. CLEAN YOUR LAB AREA!
15. Complete the conclusion questions.
EFFECT OF TEMPERATURE ON ENZYME ACTIVITY
Design a controlled experiment that would test the effect of temperature
on enzymes. Make sure your experiment has only one variable. Create a
hypothesis and illustrate (draw) your experiment on the answer sheet.