Enzyme activity

Equipment list.
- 200 mL beaker
- Fresh chicken liver
- Hydrogen peroxide (6.0% v/v)
- Stop watch
-100 mL measuring cylinder
- Scissors
- Electronic balance
- Glass rod
- Ice
- Hot plate
- Thermometer
- Ice

Safety - gloves, goggles and labcoats must be worn. Hydrogen peroxide is extremely corrosive.

During this practical investigation we will investigate the impact of temperature on the rate of an enzyme catalyzed reaction;

 

Catalase is an enzyme found in nearly all living organisms exposed to oxygen. This enzyme catalyses the breakdown of hydrogen peroxide to water and oxygen according to the equation below.

2H2O2 => 2H2O + O2

Hydrogen peroxide is a poison produced during normal cell metabolism and must be broken down before it can do damage to the cell.

Step 1 - Using a scissors finely chop up a piece of fresh chicken liver.

 

Step 2 - Weigh approximately 3.65 grams of the finely chopped liver, at room temperature.

Step 3 - Add 30 mL of distilled water and 20 mL of hydrogen peroxide solution to a 200 mL beaker and place it on an electronic balance and allow for the solution in the beaker to reach room temperature.

 
Step 4 - Add the liver to the peroxide solution and quickly zero the scales.
View the investigation on the right.

 

 

Step 5 - Record the mass loss every 30 seconds.

Using scissors or a glass rod continue to break the bubbles of oxygen so that the gas can escape. Click to see a video.

  
Continue to measure until the reaction stops. Fill in the table below
time (min) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
mass loss (gm)                                      
Graph the results on an appropriate set of axis.
Repeat steps 1-5 except this time use ice to cool the hydrogen peroxide solution to below 5 oC before placing the liver in it. Fill in the table below
time (min) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
mass loss (gm)                                      
Graph the results on the same set of axis as previously.
Repeat steps 1-5 except this time place the liver in boiling water for 5 minutes before placing it in the hydrogen peroxide solution.
time (min) 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5
mass loss (gm)                                      
Graph the results on the same set of axis as previously.

 

What is a reasonable hypothesis for this experiment? Choose from the list below.

What is the dependent variable in this investigation?
What is the independent variable in this investigation?
What do you notice about the three curves? Explain
How can you tell that the same amount of solution was used in all investigations?
When the reaction at room temperature stopped, the beaker was cleaned out and the liver removed and placed to one side. Fresh solution was added and the same piece of liver placed in the fresh solution. What do you predict would happen? Explain.

What must be kept constant in all three investigations?
1) - temperature
2) - volume of solution
3) - mass of liver
4) - size of beaker
5) - size of balance