- I will be repeating this experiment again so that I get accurate results.
Apparatus:
Risk Assessment/Safety Statement:
Hazards of amylase solution: ²
- If ingested it may cause vomiting
- If in contact with eyes it can cause irritation
- On contact with skin it can cause irritation
- If inhaled it can cause respiratory problems and even stoppage in breathing
Hazards of starch solution: ³
- On eye contact it may cause eye irritation
- On skin contact it may skin irritation
- If ingested it may cause irritation to the digestive tract
- If inhaled it may cause respiratory tract irritation
Hazards of potassium iodide solution:
- Acts as an irritant on eye contact
- If ingested it can cause irritation
- It is toxic to lungs, the nervous system and mucous membranes
- Repeated exposure to the substance can produce target organ damage
Prevention from harm:
- To prevent myself from eye irritation I will be wearing safety goggles throughout the experiment
- To prevent my skin from getting in contact with the chemicals I will be wearing a lab coat throughout the experiment
- To prevent inhalation of the chemicals I will make sure that the room is well ventilated (i.e. windows are open)
- To prevent chemicals from spreading I will make sure that my area is clean and to clean up any messes or spillages straight away
Variables:
The independent variable: I will vary the concentration of amylase solution and conduct my investigation at concentrations of 0.05, 0.025 and 0.01.
The dependent variable: I will be measuring the time it takes for the mixture to reach its achromatic point.
Controlled Variable: I will measure the temperature of the solutions when making sure that the mixture in the test tubes reaches the same temperature as the water bath. Also I will use 5cm³ of amylase solution and 5cm³ of starch solution and will also be taking intervals of 1 minute to remove a drop of the mixture to test with the iodine solution (until it reaches its achromatic point). Also the temperature of the water bath will be kept at a constant temperature (35oC) throughout the experiment.
Method:
I prepared four different concentrations of the amylase solution: undiluted, diluted to a half, diluted to a quarter and diluted to a tenth of the original concentration. Whilst doing this I made sure that the water bath was at 35oC (because I will need it later). Afterwards I pipetted 5cm³ of the undiluted enzyme solution into one test tube and 5cm³ of the starch solution into another test tube. I then left both these test tubes in the water so that the mixture can reach the temperature of the water bath. Once the undiluted amylase solution and starch solution reached the temperature of the water bath I mixed the undiluted amylase solution and starch solution together, replaced the mixture in the water bath and immediately started a stop watch.
At intervals of 1 minute I removed a drop of the mixture to test with the iodine solution on a white tile, to see if starch was still was present. I continued removing a drop of the mixture until it failed to give a blue-black colour; I recorded this as the achromatic point. I then did the same method again but this time with the different concentrations of amylase solution that I made earlier.
Results Table:
Original Results:
This is my table of results. Here the achromatic point is measured in minutes, to show how long it took for each of the concentrations to it. Also it shows each of the different concentrations of the amylase solution which was measured in cm³. Furthermore the results table shows the two set of results that I got (because I repeated the experiment twice).
Summary Results:
This summary results table shows the average set of results that I got from my experiment. To get the average results I got the results that I got from my experiment and then divided this by two. Thus this results table also shows the average achromatic point for each of the concentration of amylase solution.
Graphs:
Analysis:
I used my table of results to help me do my line graph. This line graph is showing the effect of starch solution on the activity of amylase. What I noticed was from looking at the graph was that the undiluted amylase concentration had the shortest time in minutes to reach its achromatic point. Also what I noticed that the diluted to a tenth amylase solution had the longest time to reach its achromatic point. Thus showing that an increase in the concentration of amylase solution, the shorter the time it takes for it to reach its achromatic point. Afterwards I did a line graph and it is showing the effect of starch solution on the activity of amylase. What I noticed from looking at the graph is that the undiluted amylase solution had the highest rate of reaction whilst the amylase solution that was diluted to a tenth had the lowest rate of reaction. This shows that an increase in the concentration of amylase solution increases the rate of reaction and the activity of the amylase. To work out the rate of reaction I had to calculate the reciprocal of the time taken to reach the achromatic point at each concentration of amylase. So basically I got time taken for each concentration of amylase to reach the achromatic point then divided this by 1. Then I did another graph which was a curve graph which showed the rate of reaction against the time for each concentration of amylase solution. What I found from this graph is that as the achromatic point increased, the rate of reaction decreased, and also that the reaction was highest for the undiluted concentration, which also had the also had the lowest achromatic point.
Conclusion:
My conclusion is that an increase in enzyme concentration increases the rate of reaction and the activity of the amylase. This happens because there are more collisions between the enzyme and substrate molecules since there are more enzyme molecules for the substrate molecule to collide with. What I also noticed is that the more dilute the enzyme concentration was, the slower the rate of reaction and the slower the activity of the amylase. This could be because there weren’t enough enzyme molecules for the substrate to collide with. The activity of the amylase was slow because it took long for the concentration to break down the starch substrate. Therefore the less dilute the amylase solution the faster the rate of reaction and the faster the activity of the amylase and the more dilute the amylase solution the slower the rate of reaction and the slower the activity of the amylase. This shows that my hypothesis was right because my prediction went with what happened in the actual investigation.
Evaluation:
Accuracy of Results:
Even though there were no anomalies present in my graphs, my investigation may not have been that reliable because I am judging a change in colour by my eyes. Judging the colour change by my eyes may affect these results since I had to see when the different concentrations of amylase solution stopped giving a blue-black colour. The problem with seeing a colour change by using the colour blue is that it ‘causes the eye to lose focus in the presence of all the other colours’6, so it may have been unreliable to see when the different concentrations of amylase solutions stopped giving a blue-black colour. So that is why I think that this is an unreliable subject to see a change in colours. Although by repeating the experiment again I could get a close enough result of the effect of using starch solution on the different concentrations of amylase solutions.
Repeated Test:
If I could repeat the experiment again I would repeat it probably two more times, to make my investigation more of a fair test. Also I would make sure that was to prepare the starch solution earlier before starting my experiment because I had to heat up with the Bunsen burner so that it would react properly when testing it with the different concentration of amylase solutions. This may have been a potential source of error for if I had done this earlier I would probably be able to repeat my experiment a few more times. Furthermore I would work at a faster rate so that I can repeat the experiment more times too. If I was to do further work onto this topic I would do an investigation on the effect on temperature on starch solution on the activity of amylase. I would use a different range of temperatures starting from 100C, then 20oC and then eventually going up in 10oC to see if the achromatic point will either happen at quicker times for each of the different concentrations of the amylase solutions. If I was to do this I would use the same method as before but testing the effect of starch solution of the mixtures at different temperatures of the water bath.
References:
¹ =
² =
³ =
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= ‘Essential AS Biology, Glenn and Susan Toole, Published by Nelson Thornes Ltd, Enzyme properties, pg24’
6 = http://en.wikipedia.org/wiki/Eye#Color
