The liver is a host to many different enzymes. One enzyme is called Catalase. This enzyme breaks down hydrogen peroxide into water and oxygen.
2H2O2 → 2H2O + O2
Equipment
10ml of 10% hydrogen peroxide
Pipette
1 Conical flask
1 rubber stopper
1 tube
1 tub filled ¾ with water
1 Retort Stand, boss head and clamp
1 Measuring cylinder
1 piece of liver
Method
1. Fill the tub ¾ of the way full with water.
2. Set up the retort stand, boss head and clamp.
3. Position it close to the side of the tub.
4. Fill the Measuring Cylinder with water, all the way to the top.
5. Cover the top of the measuring cylinder with your hand and turn it over. Submerge your hand until the measuring cylinder is covered in water. Slowly remove your hand and clamp the measuring cylinder in shape. You set up should look like the image on the left.
6. Using your pipette place 10mL of hydrogen peroxide into the conical flask.
7. Get your rubber stopper and tube set up.
8. Have some one hold the rubber tube under the measuring cylinder. Have some one ready with the stopwatch and have someone read to record the values.
9. When you’re ready place the piece of liver in the hydrogen peroxide and quickly close the conical flask with the rubber stopper.
How to record the data
Every 2 seconds for 34 seconds, record the total amount of oxygen produced.
Time (seconds)
Total amount of oxygen produced
2
4
6
8
10
12
14
16
18
20
22
24
25
26
28
30
32
34
To test if it really is oxygen produced. Light a splint and blow it out. Carefully remove the measuring cylinder and place the splint inside.
The splint should re-light and glow bright due to the oxygen produced.
Questions
1. What were the substrates and products in this reaction? (2 marks)
2. What is the enzyme involved in this reaction? (1 mark)
3. Explain what would happen if we cooked the liver before the experiment? (4 marks)
4. Using the data you gathered create a line graph.
Remember label the axis and use a title. (6 marks)
5. What happened at 30 - 34 seconds? (2 marks)
6. What happened to the enzymes at the end of this reaction? (1 mark)
7. What would happen if the liver was exposed to a pH of 1 prior to the experiment. Described what would happen to the enzyme, as well as the data. (4 marks)
8. Explain what is meant by the term Optimum temperature. (2 marks)
9. Explain why it is beneficial to keep our body temperature below the optimum temperature of most of our enzymes? (3 marks)
10. If we decreased the temperature of the liver, before placing it in the hydrogen peroxide, what would you expect to happen? (2 marks)
11. At circled stage on the graphs above, draw and describe what you would expect the enzyme to look and act like. (4 marks)
12. What I meant by the lock and key Method? (2 marks)
