Note: All information has been found from the web site: and from the textbooks, ‘Coordinated Science BIOLOGY’ and ‘CGP GCSE BIOLOGY’ books.
Fair Test
To make my investigation fair, I will do the following things:
- Repeat each experiment twice, therefore I will have three results for each experiment
- Use the same amount of Hydrogen Peroxide for each experiment
- Use the same type of liver, and from the same ‘actual liver’ for each experiment
- Use a sensitive scale to weigh out the liver
- Use the same equipment, such as the same beakers, Bunsen burners, conical flasks, gas syringe, etc for each experiment
- Have the liver and Hydrogen Peroxide the same temperature before being mixed together
- Have the same amount of liver for each experiment
Prediction
As the variable will be the change of temperatures, I predict that about 37˚C to 40˚C the Catalase will work its best, meaning the rates of reactions will be the fastest at that temperature. The reason for this is that since Catalase is an enzyme, enzymes generally tend to work its best at an optimum temperature and that temperature is at 37˚C. This really only applies for those enzymes which are inside living species, and in this case, a lambs liver is obviously from a lamb therefore it is a living specie.
So at lower temperatures, the rates of reaction will be slower and it will increase as the temperature increases. When the temperature reaches to about 40˚C, the rates of reaction will start to slow down again and eventually there will be none.
The reason for this is because as the Catalase becomes over heated (more than its optimum temperature), it will begin to denature, and meaning the enzymes will become destroyed. As they will be denatured, they will be useless therefore the rate of reaction will slow down and eventually come to a stop.
To prove this, you can refer to my background about the properties of enzymes and their factors, which will have an affect on the rates of reaction.
Apparatus
The equipment needed for this experiment will be:
- Lambs Liver
- Hydrogen Peroxide
- A 100ml conical flask
- A delivering tube
- 250ml beakers
-
A 100cm3 gas syringe
- Stirring rods
- Scalpels
- A balance
- Thermometers
- A stopwatch
- A measuring cylinder
- A square tile
- A stand with clamps
- Bunsen burners
- Plastic gloves
- Pen and paper
Method
- Firstly collect all the equipment needed for the experiments, and cut a big chunk of liver
- Now place the liver in a bowl, and grind the liver into small pieces
- Measure the amount of Hydrogen Peroxide needed, via using a measuring cylinder and place it in a clean beaker
- Switch on the scales and place the square tile on top
- Now use a scalpel to scoop the liver onto the tile, weighing the amount needed
- Once weighed, place the liver into another beaker and fill two large beakers half filled with water
- After that, set up the Bunsen burners and switch them on, heating up the two beakers of water
- Now place the liver into one of the beakers of water and heat it up to the required temperature. (Don’t forget to add a thermometer into the water to show what the temperature is)
- Then place the measured out Hydrogen Peroxide into the other beaker and also heat that up to its required temperature
- While it is heating, get a stand and attach the gas syringe onto it with its delivering tube and conical flask
- Now once the liver and the Hydrogen Peroxide has been heated enough, quickly add them both into the conical flask and put the bung (attached to the delivering tube and gas syringe) on top
- At the same time, start the stop watch and time the for 30 seconds and record down the amount of gas produced in that amount of time in, via looking at the gas syringe
- Once done, wash all the equipment and repeat the same experiment again for another two times
- After, do the exact same experiment again for the rest of the different temperatures and so on.
Safety Rules
There are a few safety procedures in which you will need to know to carry out these experiments safely. Firstly, you must wear goggles for this experiment, as Hydrogen Peroxide is known to be poisonous.
You should tuck in your ties and hair (if long) as burning will be required, you should be careful not to let the gas syringe fall out at the end, when the gas collected has become too much, you should watch yourself when cutting the liver with the scalpel and to take care not to touch the tri-stands when hot, or to be careful when taking out the beakers, etc.
Prework
For this investigation, I have done two preliminary works.
At the start, I planned to use 0.1g of liver and 20ml of Hydrogen Peroxide for each experiment. I timed how long it would take for 50cm3 of gas to be collected in the gas syringe. So to make sure that these ranges and methods were suitable enough, I had done the experiment. What happened was that, none of the temperatures used for the experiment produced 50cm3 of gas, therefore I could not produce any results. Because of this, I have thought of another range and method. I thought that as not enough gas was produced, I would need to increase the amount of liver and so…
My second prework was to use 0.5g of liver and 30ml of Hydrogen Peroxide for each experiment. This time, I timed the experiment for one minute to see how much gas would be collected. In the end, I also did not produce any results as each of the experiments had produced more gas than the actual gas syringe could record, therefore the syringe popped out from the other end!
As of this, I have now produced a better method and range to be used. This time the amount of liver is in between 0.1g to 0.5g and so it should now produce the right amount or enough to show a decent set of results. These are shown in the ‘range’ section.
Range
The variable I have chosen for this investigation is the change of temperature. The amount of liver to be used for each experiment will be 0.2g and the amount of Hydrogen Peroxide will be 25ml.
I will time how much gas will be collected in 30secs!
Results
Here are the results from all the experiments. I have repeated each experiment twice and therefore have done a total of three experiments for each. The amount of gas collected is measured in cm3 and the temperature is in ˚C.
I have timed each experiment for 30 seconds and recorded its amount collected straight away.
I have calculated the average amount of gas collected for easier viewing. The average results have been rounded up into two significant figures.
Accuracy
As you can see, the results obtained look fairly accurate. I have tried my best to make them as accurate as I can. I have kept all the other variables constant, I have used the same equipment for each experiment and the liver and Hydrogen Peroxide were heated to the correct temperature before being mixed together. Overall, these results are reliable enough to support a firm conclusion.
Conclusion
What I have found out
From looking at my results, I have found out that the amount of gas collected increases as the temperature increases and then it drops back down again. At the start at 30˚C, the Catalase in the liver was working very slowly in the Hydrogen Peroxide solution. As it was reacting slowly, the amount of gas (oxygen) produced was less; therefore the amount of gas collected in the gas syringe was less too. As the temperature went up to about 40˚C to 45˚C, the Catalase had reacted mush faster and therefore the rate of reaction was also faster. As of this, it produced more gas, meaning that a lot more gas was collected in the gas syringe. After about 45˚C, the rate of reaction started to slow down again as the Catalase were becoming denatured. As some of the Catalase was becoming denatured, it meant that there was less of Catalase, meaning a much slower reaction having less gas given off.
The reason for this is happening is because Catalase (enzymes) works best at an optimum temperature. This temperature is usually around 37˚C. So when the temperature was low, the Catalase were mostly inactive or working really slowly. As the temperature increases, the inactive Catalase then becomes active again and starts to speed up the rates of reaction much faster. When the temperature reaches to its optimum temperature, the Catalase speeds up the reaction at its fastest. But as the temperature carries on rising, the Catalase then becomes denatured and is useless. The result of this was less gas produced and therefore a slower rate of reaction.
As you see on the table, my results were not as clearly shown. The rate of reaction was at its fastest at round 45˚C where it was meant to be at about 37˚C. The reason why my set of results are like this is because of some inaccuracies and that the Catalase denatures at different times. As the Catalase denatures at different times, this has probably affected the results, meaning the reaction rates were slightly different from normal.
As I have said, mainly majority of the enzymes will have their optimum temperature at 37˚C, but in this case, Catalase seems to have a slightly higher optimum temperature. But then again, this may not be the case as there were also some inaccuracies.
Note: When the Hydrogen Peroxide reacted with Catalase, they produced Oxygen (which was the gas) and Water!
Was your prediction correct?
What I have predicted is kind of correct. The temperature, which shows the fastest rate of reaction, is at 45˚C in my results and I had predicted about 37˚C. Even though it has been higher than I had expected, it still showed the similar pattern how an enzyme works. The aim of this investigation is to investigate the enzyme activity; therefore I can tell you that the temperature affects the enzyme activity. There is an optimum temperature, which the enzymes work best at, and after that temperature, they become denatured and so on.
Overall, I was not far off from my prediction and even though the results are a bit out of place, they are good enough to support my prediction and to make a valid conclusion.
Graph
To show my results in a better way, I have also produced a line graph. As you see on the graph…it does look a bit similar like the one I have drawn in my background. The rate of reaction is slow at the start and then increases with its temperature. After, the rate of reaction reaches to its peak (enzyme’s optimum temperature) and then it slows down again, because of the denaturing of the enzymes. This pattern is clearly seen on the graph.
(See Last page)
Evaluation
Relevant comment
Throughout this investigation, I have worked quite well and it was relatively easy to do. The main thing was that it took a long time to complete as the liver and Hydrogen Peroxide took awhile to heat up. Although the results obtained were slightly inaccurate, they were still good enough to be counted to make a valid conclusion and to support my prediction.
Even though I do not like playing with liver, I have enjoyed doing this experiment very much.
Accuracy and Erroneous points:
The accuracy of my results were not so accurate but were enough to see the pattern of how the temperature affected the enzyme activity. In the end, I did not use the ‘same liver’ for each experiment as about three lessons were needed in order to complete the experiments. As these lessons were not one after another, and were days apart, a new lamb’s liver was brought into each lesson and the old was thrown away. Each individual liver may have different types of Catalase. Some could have been more resistant to the heat than others, therefore will not be denatured as quickly. This is a point in which I did not consider at the start and it may have been the major source in affecting the results.
Also, another inaccuracy is that as I weighed the liver and placed it on the tile, I had to scoop it into the beakers and then into the conical flask. As of this, some of the liver may have been left, meaning that the liver would be actually less than the real amount. It was very hard to get the liver into beakers and out, as they tend to stick onto the sides, etc. They also stuck onto the scalpel!
Reliability:
The results, which I now have, are reliable enough to tell me whether my prediction is correct and to make a valid conclusion. There are also enough results done to make it fair. I also have enough evidence in the results to support all my points.
How to improve Method and Accuracy:
Since I have taken about two to three lessons to complete my experiments, to improve my accuracy of the results and the method, I could have carried out all the experiments on the same lesson / day. The reason for this is so that I will get to use the same liver and not two different ones (as each lesson is supplied with a new liver). If this were to be done, then the same Catalase would have been used meaning it would be fair and more accurate. I can also improve the method by some how managing to weigh the liver without needing to touch anything, as then it won’t have the chance to stick to things losing more liver, losing more Catalase!
Extension to work:
To extend my work on this investigation, I will probably extend the temperatures so that I could see whether the Catalase would totally denature, meaning the rate of the reaction would stop and therefore no gas given off. Apart from this, I cannot really think of any more extensions to investigate the enzyme activity using temperature as the factor.