Apparatus
2 Test tubes, test tube rack, 10ml. Syringe, dimple tile, iodine solution, starch solution, amylase solution, glass rod, 250ml. Beaker, stop clock, thermometer, container full of ice, marker pen, water bath set at temperatures 20oc, 30oc 40oc, 50oc 60oc, 80oc.
Safety precautions
I will need to wear safety goggles, tie my hair back, be careful with the iodine solution because it can stain clothes and be careful when handling boiling water. Clean up any spillages and be careful when electricity and water are about. I must not eat or drink in the lab.
Method
- With a clean syringe, correctly measure 10ml. Of starch solution into a test tube. Check that there are no air bubbles.
- Wash the syringe and measure 1ml. Of amylase solution into the other test tube. Label each tube with your initials. Stand both tubes in the ice/water bath/boiling water depending on which temperature you want your solutions at. This will take between 5 and 10 minutes.
- While you are waiting, put 2 drops of iodine solution in each dimple tile. Put some water into the beaker and wash the glass rod.
- When the tubes reach the correct temperature (you can tell by using the thermometer), leave them where they are and start the clock, Quickly pour the starch solution into the amylase, stir the mixture with the glass rod, take out one drop and put in into the iodine on the tile. (In the first experiment there will be starch present so it will go black).
- After use of the glass rod, clean it in the beaker of water. After 30 seconds, repeat by stirring and removing one drop and putting it into the iodine on the tile.
- Repeat steps 4 and 5 until the iodine doesn’t change colour when the solution is added. (This means that all the starch has been broken down). Record the results in a table as you go along.
The only variable that will be changed on each experiment is the temperature. Other variables are using different amounts of starch and amylase for each test, and doing the experiment in different ways. There are 6 different temperatures that the experiment will be done at each temperature will be tested 3 times to get an average. The experiment will be done as a group; I will only do the experiment at one temperature.
Results
These are the results we got as a class:
Obtaining evidence
I am going to observe how long it takes starch to be broken down by amylase at different temperatures and the rate of reaction against temperature.
Safety precautions
To ensure complete safety in the lab while experiments take place, people must: -
- Wear safety goggles
- Tie long hair back
- Be cautious with the iodine solution because it can stain clothes
- Be careful when handling boiling water.
- Clean up any spillages
- Take care when electricity and water are about.
- Not eat or drink in the lab.
- Be careful not to spill chemicals and not to get them on your skin and eyes
- Take care not to drop or break test tubes or any other form of glass.
Apparatus
The apparatus needed in the experiment are: -
2 Test tubes, test tube rack, 10ml. Syringe, dimple tile, iodine solution, starch solution, amylase solution, glass rod, 250ml. Beaker, stop clock, thermometer, container full of ice, marker pen, water bath set at temperatures 20oc, 30oc 40oc, 50oc 60oc, 80oc.
These are the observations that we took: -
Conclusions
The graph that shows rate of reaction against temperature shows that when the temperature is low, the reaction takes place very slowly. As the temperature rises, the reaction happens faster. The reaction is at its fastest at 40oc and carries on reacting at this speed until 50oc. When the temperature reaches 60oc the enzymes begin to denature, so the whole experiment is slowed down. When the temperature reaches 70oc the reactions has come to a halt which means that the enzymes have completely denatured.
In the graph that shows how long it took the starch to be broken down by amylase at different temperatures, you can see that at 0oC the reaction was at its slowest. As the experiment is repeated at higher temperatures the reaction speeds up to its fastest at 400 C. After 50oc the enzymes begin to denature and eventually stop working.
The graphs both show the same results; when the temperature is low the reaction is slow, when the temperature gets to 40oc the reaction is at its fastest. After 60oc the enzymes denature.
The original prediction fits in with the results. It’s not word by word exact though because I said that the reaction would be its fastest between 35 and 40oc but it was at its fastest between the temperatures 40 and 50oc. I also thought that as soon as it got to 60oc the enzymes would denature and not react at all but that was when the started to denature; the reaction slowed down at 60oc but the temperature had to get even higher for them to completely denature. The reason that the enzymes denatured at a higher temperature than predicted was that the enzymes we used were manufactured (we used starch and amylase) so they can stand a higher temperature.
40oc is close to the average human body temperature which means enzymes inside us are usually working at their fastest speed all the time.
Evaluation
Because different groups within the class achieved similar results, we can assume that the class results were accurate, reliable and suitable. Our results also correspond to scientifically proven experiments and textbooks.
An improvement that could be made is to make an extension to the experiment and make it even more accurate by finding out the optimum temperature; we know that it is around 40 0c. If we had more time we would do the experiment at every 0c from 35oc – 45oc. Doing this would find out exactly when the reaction is at its fastest.
