Enzyme and substrate at 25ºC Enzyme and substrate at 45°C
Enzyme Enzyme
Substrate Substrate
However, if you pick a temperature such as 75°C, you get the reverse effect. The temperature is too high and the enzyme molecules begin to vibrate so violently that the delicate bonds break. These broken bonds are irreversible because it changes the shape of the enzyme. The substrate can no longer fit with the enzyme and so no reaction occurs. This is known as the enzyme being denatured.
Below is a diagram of what happens at a low temperature.
Below is a diagram of what happens at a higher temperature, the enzyme is denatured. The enzyme has changed shape. So, the substrate no longer fits with the enzyme.
Every enzyme has an optimum temperature. This is the temperature at which an enzyme catalyses a reaction at the maximum rate. The optimum temperature for the reaction between amylase and starch is 52.5°C. I got this figure from my graph by using a line of best fit. I know that this is the optimum temperature because the line starts to decrease after 52.5°C.
On my graph, between points A and B the temperature is increasing and so is the relative rate of reaction. At these points the molecules are colliding extremely fast to break the substrate into its products, maltose. However, after point C, as the temperature is increasing, the relative rate of reaction decreases. After C, the substrate and enzyme no longer fit together, so the reaction cannot be completed. This is why there is no reaction.
There are several possible sources of error in this experiment and they can be improved. The amount of iodine that used by each participant. The more iodine that is added to the solution, the darker the iodine would look. So, if one participant put two drops of iodine in the solution and another put four drops of iodine, this would cause an unfair reading. One participant could mistake the dark colour of iodine for the blue/black colour present in starch. A possible solution for this could be to state how many drops of iodine to add to the solution to save confusion. However, each drop contains a different amount of iodine. So, a piece of equipment that measures the exact amount of iodine added to the solution would be ideal to prevent any possible error.
Different participants have different opinions about whether starch is present or not. The fairest solution I can think of is that one participant does every experiment. This would provide the same opinion throughout the experiment. However, this could become very tedious and time consuming so this would not be an ideal solution.
Some participants may not have tested the amylase and starch solution at exactly one minute. This causes an unfair test because the difference of a couple of seconds can effect whether there is starch present or not. Also, some people had to travel from the water bath to the dish where they were experimenting. This would add even more seconds onto the stopwatch and cause further error. I would suggest keeping their dish and the water bath close together so they can test the solution as close to the minute as possible. However, when experimenting with such a large group, this may not be practical or safe due to lack of space.
Starch does not dissolve in water, it has a suspension characteristic. This means that the starch would sink to the bottom of the beaker or test tube. So, the solution at the top of the beaker or test tube would have a lower concentration than the solution at the bottom. This makes the experiment unfair. One possible solution would be to stir the solution before you take a sample. Or, have a piece of equipment called a magnetic stirrer that constantly stirs the solution.
As soon as the test tube is taken out of the water bath, the temperature starts to decrease. This would cause an unfair reading. I would suggest taking a sample from the test tube while it was still in the water bath preventing any decrease in temperature.
People doing room temperature at 25°C. If one participant testing room temperature was doing her experiment next to the window, this could cause a lower temperature than someone how was standing next to the water baths. To make the test fairer, I would make sure that all windows were closed and temperatures were constantly taken from the test tube to make sure it stays at 25°C.
If all the criteria above were met, the experiment would be fairer and the result would be more reliable.
I believe that the optimum temperature is 52.5°C. To prove if I am right, I could test the enzyme at more precise temperatures between 45°C and 60°C. For example every second degree, 45°C, 47°C, 49°C, and so on.
To improve the experiment I could also take the readings more often. For example every 30 or 20 seconds. This would make the experiment more accurate to see when the enzyme reaches achromatic point.
