The actual effect of temperature on the rate of reaction is the combined influence of these two factors.
METHOD
- Set up the apparatus as shown
- Measure 1ml of catalase and 20ml of hydrogen peroxide.
- Make shore that they are at the right temperature, which is 10 degrees .
- Pour them in to the conical flask, place the bung on firmly and quickly. To prevent any loss of oxygen gas.
- Record the amount of evolved gas Avery 30 seconds until 3 minutes.
- Carry out this procedure twice then find the average. This is to insure accuracy.
- Repeat the experiment with the following temperatures 10,20,30,40,50,60,70and 80 degrees.
- Remember to keep the concentration the same and the time.
- Repeat the whole experiment, but this time only increase the temperature of only the substrate.
- Record the results.
- Repeat the whole experiment, but this time only increase the temperature of the enzyme.
- Record all your results.
FAIR TEST
I made this experiment fair:
- By keeping the concentration of the enzyme and hydrogen the same.
- Keeping the volume of the enzyme and hydrogen the same.
- Using the same equipment each time (washing them between every experiment).
- Changing one variable at a time.
The things that made the experiment not fair were:
- Putting the bung in the conical flask, this is because oxygen gas is lost. But this error shouldn’t make a great difference because in every experiment the same error occurs.
- Keeping the enzyme at the right temperature. This was difficult because the enzyme temperature falls when it is poured into the conical flask. This error shouldn’t make hardly any difference because the same error accurse in every experiment .You could probably over come this error by heating the enzyme a bit extra, so that when it is poured in the conical flask it would have the right temperature. But this may lead the enzymes in becoming denatured.
- There was a bubble in the thermometer.
- There was not enough enzyme and hydrogen peroxide solution.
- There was not enough time, as every lesson we had to do all the experiments again because of the different concentrations of the enzymes.
- Lack of equipment, which made it hard to use the same equipment every time.
ALL THESE PROBLEMS MAY RESULT IN UNRLIBLE RESULTS.
RESULTS
Increasing the temperature of both hydrogen peroxide and the enzymes.
Increasing the temperature of only the substrate.
Increasing the temperature of only the enzyme.
CONCLUSION
My result were not accurate due to the problems, but they still show that as the temperature increases the rate increases. Also as the reaction progresses the rate slows down because hydrogen peroxide is being used up and water is being produced. This is because hydrogen peroxide added to catalase gives water plus oxygen gas (2H2O2 catalase 2H2O+O2 ) and when the temperature is high, the three-dimensional shape of the enzyme is altered to such an extent that their active molecules sites no longer fit the substance. This enzyme is said to be denatured. Increasing the temperature of only the substrate had the best effect on the rate.
Temperature is not the only thing that changes the rate of oxygen produced.
- Concentration
- pH
- Inhibition
All these and probably more, change the rate of oxygen produced
Concentration
When you increase the concentration there will be more chance of collision between hydrogen peroxide and catalase. Eventually the concentration will decrease and so will the rate because hydrogen peroxide molecules will be changed to water.
The rate of reaction is directly proportional to the concentration until after the point were hydrogen peroxide changes to oxygen and water.
Increasing the concentration is said to have a greater affect the increasing the temperature.
PH
By breaking the hydrogen bonds, which give enzyme molecules their shape, any change in pH can effectively denature enzymes.
Each enzyme works best at a particular pH, and any change from it’s normal optimum may result in denaturation .
Inhibition
The rate of enzyme-controlled reactions may be decreased by the presence of inhibitors. They are of two types. Reversible inhibitors and non-reversible inhibitors.
Reversible inhibitors
There are two types of reversible inhibitors:
- Competitive inhibitors
- Non-competitive inhibitors
Competitive inhibitors
They compete with the substrate for the active sites of enzyme molecules. The inhibitor may have a structure, which permits it to combine with the active site. While it remains bound to the active sites, it prevents substrate molecules occupying them and so reduces the rate of the reaction.
If the concentration of substrate is increased, less inhibition occurs. This is because, as the substrate and inhibitors are in direct competition, the greater the proportional of substrate molecules the greater their chance of finding the active sites, leaving fewer to be occupied by inhibitors.
Non-competitive inhibitors
They do not attach themselves to the active sites of the enzyme, but elsewhere on the enzyme molecule. They alter the shape of the enzyme molecule in such a way that the active sites can no longer be properly accommodate the substrate.
Non revisable inhibitors
They leave the enzyme permanently damaged and so unable to carry out its catalytic function. The bonds maintain the shape of the enzyme molecule. Once broken the enzyme molecule structure becomes irreversibly altered with the permanent loss of its catalytic properties
Another experiment, which I could do, is to measure the volume of the mixture of enzyme and hydrogen peroxide before and after the experiment.
This experiment could be done by:
- Set up the experiment as shown.
- Measuring 2ml of catalase and 20ml of hydrogen peroxide.
- Pour them in the conical flask and let them react for three minutes.
- Make show that in each experiment that the concentration is the same, the temperature is the same and the time is the same.
- After the experiment pour the mixture into a measuring cylinder and record the results and find the difference between the volume before and after the experiment.
- Try doing the experiment with different temperatures and seeing what happens to the volume of the mixture after the experiment.
- You could also do this experiment by changing the concentration.
- But make shore that you change one variable each time.
