Investigating the factors affecting peroxidase enzyme activity

will be more successful collisions. When it goes past the

optimal temperature the enzymes will start to become

denatured.

There is a relationship between temperature and rate of

reaction. For every 10-degree rise in temperature the

rate of reaction will double. (Q10=2)

PH is similar to temperature. Enzymes have and optimal Ph and anything either side of this will denature the enzyme.

Enzyme concentration can be raised by adding more of the enzyme or lowered by adding less. As it is raised the rate of reaction will increase. But this is only true if you have enough substrate present throughout.

The reason an increase in concentration will increase the rate of reaction will create more active sites, and there will be a greater chance of successful collisions.

Increasing the concentration of the substrate will also increase the chance of a successful collision.

Peroxidase is an enzyme which breaks down hydrogen peroxide, a toxic substance, into oxygen and water. It can be found in the liver, in potatoes and avocado.

The equation for this process is:

Hydrogen peroxide Peroxidase oxygen and water

H2O(aq) Peroxidase O2+(g) 2H2O(L)

Apparatus

* 5% avocado extract for the peroxidase enzyme

* 5% hydrogen peroxide solution

* Water baths

* A stop clock to time each experiment accurately

* A measuring cylinder to measure the amount of oxygen released during the reaction

* Delivery tubes

* Trough

* A thermometer so I can change the temperature accurately

* Rubber stoppers

* Goggles and other safety equipment

Method

. First of all I will set up the

apparatus as they appear in

the diagram.

2. I will place 30ml of 5%

Hydrogen peroxide solution

in the conical flask & add 2ml

of the 5% peroxidase solution.

Then I will quickly place a

rubber stopper on the flask.

3. Now I will follow the reaction

at different temperatures to get a good range of results. The temperatures I will be using are 0°c, 20°c, 40°c, 60°c and 80°c. I have chosen these temperatures because preliminary experiments have shown that the reaction works at a reasonable speed with this steady increase.

4. Before I add the avocado extract I will stir the solution to ensure that there is an even distribution of the enzyme.

5. Oxygen gas will be collected for 10 seconds at each temperature. The volume of oxygen gas collected will be recorded.

6. I will now repeat the test 5 times to get an accurate result.

Fair test To make it a fair test I will ensure that the volumes of hydrogen peroxide and enzyme stays the same. I have to keep the ph stay the same too. Otherwise the enzyme could become denatured. The temperature that we are studying the reaction at must also is kept the same.

I will also follow all the necessary safety precautions.

Prediction I predict that the rate of reaction will be at its peak during the optimal temperature. This is because it has more energy to go fast, the collision theory, without so much heat that the enzymes become denatured.

I think that the rate of reaction will double at every 10° rise in temperature. However, once the optimal temperature the rate of reaction will begin to decrease with the denaturing of the molecules.

Volume collected at 10s (cm ) Initial rate of reaction - volume of Average

oxygen collected (cm /min) Temperature (0°c) Test 1 Test 2 Test 3 Test 1 Test 2 Test 3

0 1ml 1ml 2ml 6 6 12 8

20 6ml 7ml 5ml 36 42 30 36

40 28ml 29ml 30ml 168 174 180 174

60 5ml 7ml 8ml 36 42 48 40

80 0 0 0 0 0 0 0

Analysis The temperature increases from 0°C to the optimal temperature (40°c).

At 0°C the initial rate of reaction was 8 cm /min. At the optimal temperature the initial rate of reaction was 174 cm /min.

My results confirm my prediction, the rate of reaction was highest at the optimal temperature. However, they did not double for every 10° rise in temperature.

Evaluation I think that the method was a good one, and reliable as it was repeated. It was not too hard to set up and carry out so there is a reduced chance of making a major mistake.

I could have improved the experiment collecting the gas in a syringe instead of a cylinder as there would be less chance of any gas escaping. I could have kept the enzyme and substrate in a water bath for longer to ensure that they were at the correct temperature. I could have left more time for the enzyme to be denatured. The reliability could also have been improved by repeating the experiment more times and trying a wider range of temperatures. I if had used ph buffers I could have made sure the ph level was always stable.