The Effect of Substrate Concentration on the Activity of the Enzyme Catalase

The Effect Of Substrate Concentration On The Activity Of The Enzyme Catalase

Aims

This is an experiment to examine how the concentration of the substrate hydrogen peroxide affects the rate of reaction of the enzyme catalase.

Background Information

Enzymes are protein molecules. They are used to speed up specific reactions in the cells. They are all very specific as each enzyme just performs one particular reaction.

Catalase is an enzyme found in food such as potato and liver. It is used for removing Hydrogen Peroxide from the cells which is the poisonous by-product of metabolism. Catalase speeds up the decomposition of Hydrogen Peroxide into water and oxygen as shown in the equations below.

Formula:

Catalase

Hydrogen Peroxide ----------> Water + Oxygen

Catalase

2H2O2------------------->2H2O+O2

It is able to speed up the decomposition of Hydrogen Peroxide because the shape of its active site matches the shape of the Hydrogen Peroxide molecule.

Apparatus

1. Gas Syringe

2. Metal Stand

3. Yeast Catalase

4. Hydrogen Peroxide

5. Test Tubes

6. Beakers

7. Test Tube Rack

8. Stop Watch

9. Pipette

10. Pipette Filler

11. Tap Water

Method

To test out how the concentration of hydrogen peroxide affects the rate of reaction first set up the apparatus below.

1. Add 2cm3 of yeast to one test tube. Add 4cm3 of hydrogen peroxide solution at a concentration of 20% to the other test tube. Use a pipette to measure out the volumes. It is very important to accurately measure the amounts of Hydrogen Peroxide, Yeast and water to ensure a fair test.

2. Pour the hydrogen peroxide solution into the test tube containing the yeast and immediately put the gas syringe bung on the end of the test tube, at the same time start the stopwatch.

3. Bubbles should start to rise up the tube and the gas syringe will move outwards, as soon as the gas syringe passes the 30cm3 mark stop the stopwatch and note the elapsed time down to the nearest 1/10th of a second.

4. Repeat the experiment with hydrogen peroxide concentrations of 16%, 12%, 10%, 8%, 4% and 0%. The 0% concentration of hydrogen peroxide solution is done as a control solution to show that at 0% concentration no reaction occurs. The different concentrations of Hydrogen Peroxide are made by adding tap water to the 20% Hydrogen Peroxide in the correct amounts. The table below shows what amounts of Hydrogen Peroxide and water are needed to make the solutions.

Concentration Of Hydrogen Peroxide Volume Of Hydrogen Peroxide (cm3) Volume Of Water (cm3)

20% 4 0

16% 3.2 0.8

12% 2.4 1.6

10% 2 2

8% 1.6 2.4

4% 0.8 3.2

0% 0 4

5. Repeat all the tests at least three times so that an average can be obtained. Repeating the experiments several times will help to produce better and more accurate results as any inaccuracies in one experiment should be compensated for by the other experiments. Note all the results in a table such as the one below.

Hydrogen Peroxide Concentration 0% 4% 8% 10% 12% 16% 20%

Time Taken (Test 1)

Time Taken (Test 2)

Time Taken (Test 3)

Average of the Tests

Rate

The rate can then be worked out by

Rate=30/Average Time

This gives the rate in cm3 of oxygen produced per second, this is because I am timing how long it takes to produce 30cm3 of oxygen. From these results a graph can be plotted with concentration on the x-axis and time taken on the y-axis.

I am using yeast catalase as opposed to catalase from apples, potatoes or liver because it is