As you can see from above, the substrate I will be using is Hydrogen Peroxide, the enzyme is Catalase and the products of the experiment are Oxygen and Water I will measure the height of the foam produces from the reaction, (the foam is produce when oxygen reacts with the detergent that is added) and how I will make my results reliable is by repeating my experiment. I will do the experiment once and then repeat it twice to make my result more reliable.
Prediction
I predict my optimum temperature for the enzyme catalase to be between 35°C - 40°C.The optimum temperature that Hydrogen peroxide is broken down by catalase in the body is 37°C. An increase in temperature will increase the kinetic energy of the enzyme and substrate molecules. In the case of enzymes, this will mean that the increased movement of both enzyme and substrate molecules will result in more collisions between them, and more successful conversions of the substrate into the product. If, however, the temperature rises above a certain point, the heat will denature the enzyme, meaning the heat will change the shape of the enzyme and the active site will no longer fit the substrate. Cold temperature, on the other hand, slows down enzyme activity by decreasing molecular motion.
Variables
The dependent variables that I aim to measure is the height of the foam the occurs when the enzyme catalase reacts with the substrate hydrogen peroxide, I will measure my results in millimetres (but this can also be measured in Centimetres.) While the independent variable that I am going to change is the temperature, I will use the temperatures –
20°C 30°C 40 °C 50 °C 60 °C
The controlled variables in this experiment are – the with and length of the potato as this is where the catalase enzyme is taken from the length should be 1cm and the width 5mm, It’s also important to have the same type of potato and the same age of the potato, the same volume of hydrogen peroxide used in each experiment which is 10cm3 and also the same pH of detergent and the same amount of detergent used the pH is 7 and the amount I use done drop of detergent.
Apparatus
Potato
Hydrogen Peroxide
Detergent
White Tile
Cork borer no.4 and 5
Test Tubes
Test Tube Rack
Knife
Measuring Cylinder
Beaker
Stop Clock
Ruler
Water Baths
Thermometer
Forceps
Distilled Water
Dropper
Safety
There are a few safety precautions that need to be taken such as safety glasses being worn to protect the persons eyes. Hydrogen peroxide is an irritant so it is important that It does not come I contact with the skin as it could cause burns. It could also seriously damage your eyes so that is why it is important to wear safety glasses at all times.
Method
- Prepare a table to record results of your findings
- Prepare a potato cylinder, which is used by putting cork borer 5 into a piece of potato and then pushing the piece out using cork borer 4
- Cut the potato cylinder so it is 1 cm in length
- Prepare 3 test tubes each containing 10cm³ of Hydrogen Peroxide
- Heat the potato and Hydrogen Peroxide separately to the desired temperature in the water bath.
- Add a drop of detergent to the hydrogen peroxide and then add the potato cylinder
- Time the experiment
-
Measure the height of foam that is produced when catalase reacts with Hydrogen Peroxide of 10cm3. Measure the height of the foam every minute for five minutes in millimetres.
- Record results
- Then add three new test tubes to a water bath with the temperature at 30˚C
- Set up the apparatus in the same way as you did at room temperature, and carry out the experiment in the same way as you did at room temperature, the only change being this time is that the temperature the experiment is happening at is different
- Again record your results
- Carry out the experiment again for the temperatures 40˚C, 50˚C and 60˚C and record you findings for each.
- Repeat your experiment twice to improve reliability and make sure when recording results it is measured to the nearest millimetre to improve accuracy
Strategy for results
I will find the average of foam over 5 minutes from the 3 readings. I will record my results in a table form (as shown below) and then I will draw two graphs displaying my results; a straight line graph and a line of best fit graph. The Y-axis on my graph will be the height of the foam produce, this will be measured in millimetres and on my X-axis it will be the time in minutes.
The equation I will use to find the average height of foam will be-
Original experiment + Repeat experiment 1 + Repeat experiment 2
3
Average height
of foam (mm)
Time (mins)
Interpretation and Evaluation
I found the optimum temperature to be 40°C, I know this as it is the steepest line on my graph. As the temperature increased from 20°C to 40°C the rate of reaction increased this is because there is more kinetic for the substrate and enzyme molecules therefore more collisions will occur, meaning more successful collisions between the enzyme and the substrate.
Denaturation occurs when the temperature exceed the optimum. When enzymes are heated up too much they vibrate so vigorously that the bonds holding the enzyme in its specific shape break. The enzyme shape changes and the substrate no longer fits in to the active site. An enzyme which has become denatured is permanently inactive and will take no further part in reactions. Denaturation normally occurs at around 50°C – 60°C.
There were a few problems that occurred in my experiment, oxygen had escaped as some bubbles had burst when we were doing our experiment, meaning a loss in oxygen. An alternative method to help this problem would be to use a gas syringe with a side arm tube to measure the volume of O2 produced.
Another factor that affected my results was that there was a time limit, and I could only manage to repeat the experiment twice. If I had more time I could have repeated my experiment more times, which would have made my results more reliable. Also I would repeat the experiment using smaller temperature intervals to determine a more accurate optimum temperature, possibly going up in 2˚C instead of the 10˚C that we done.
I predicted that the optimum temperature would be roughly around 40°C, I found that here my results agreed with my prediction. I predicted that the enzyme would completely denature at 60°C, but I found that this was not the case as I can see from my graph that there was still some enzyme activity at 60°C. This could be because not all the potato was heated to 60°C. The centre of the potato may have been lower than 60°C meaning a reaction could still occur as not all the bonds in the enzyme had denatured.
The results did not support a firm conclusion, as it was only repeated twice because I did not have to repeat it more times. Ideally it should have been repeated ten times. When I compared my results with my classmates, the results varied as some peoples optimum temperature was 30˚C and others was 40˚C, but everyone got the same trend out of the same experiment under the same tightly controlled conditions. The trend was that as temperature rises to the rate optimum, rate of reaction increases and as the temperature passes the optimum the rate of reaction decreases.