It can be seen that up to 40 oC the enzymes were working faster until the temperature increased higher than 40 oC, which meant that the enzyme was taking longer to react and breakdown the starch. The enzyme took longer to react at the higher temperatures as enzymes become denatured at high temperatures and as the temperature increased the more the enzymes started to become denatured, therefore it caused the rate of reaction to decrease. Enzymes become denatured, as they are proteins; therefore an increase in temperature will cause the shape of the enzyme molecule to change irreversibly. The diagram below shows the “lock and key hypothesis” which shows the ways enzymes usually work.
The diagram shows how an enzyme works do break down the substrate molecules by the enzyme molecule locking on to the substrate molecule. When an enzyme becomes denatured the enzyme molecule changes shape irreversibly, therefore, the enzyme molecule does not lock on a substrate molecule and break it down. This is why the enzyme is denatured as denatured means destroyed; the enzyme molecule has been destroyed so it no longer does its job of breaking down the substrate molecules, which in this investigation would be the starch molecules. This is why in the investigation the rate started to decrease as the enzyme became denatured; therefore the amylase enzyme was not breaking down the starch molecules.
The temperature at which the rate was fastest was 40 oC; this is as enzymes work best as certain temperatures. In humans it’s 37 oC, this is round about the right temperature for amylase as it’s found in the mouth.
It can also be seen on the graph that the rate for 30 oC is quite a bit off the curve, this could be due to many different reason which meant that the investigation wasn’t a fair test.
Firstly, it could have been because the results weren’t accurate, as when the iodine wad placed in the spotting tiles, one drop was placed in each tile using a pipette, which made it difficult to place the same amount in each tile, so this could have made it an unfair test causing the result to be wrong.
Another reason the result was off the curve could have been because of the amount of amylase and starch solution that was placed in the iodine. It was placed in the iodine using a glass rod, which made it hard to put the solution if any into the iodine. Moreover, when placing the solution into the iodine it was hard to tell if all the starch had been broken down, as it was hard to tell wherever the iodine was back to its original colour, so the experiment could have been timed for too long or not long enough as it was hard to tell if the iodine was actually back to its normal colour, therefore the starch might not have been completely broken down.
Therefore, this means that the time taken for the starch to be broken down was not very accurate due to the fact it was hard to tell if the iodine was back to its original colour. However, the time taken could be quite accurate as I placed the amylase and starch solution into the iodine every 30 seconds this meant that the next time I placed the solution into the iodine I had a realistic change in the colour as I had given a realistic amount of time for the amylase to break down the starch. I could have made it more accurate by using a pipette to place the solution in the iodine, as it would mean that I did had a drop of the solution in the iodine, making the results for time more accurate.
All these reasons could have caused the plot on the graph to be off the curve when the temperature was at 30 oC. As the plot on the graph was off the curve it probably means that my results are unreliable.
Looking at my table my repeat reading are quite different to the first ones. This probably means my results are unreliable as it shows that the repeat readings have been done differently to the first ones. This could mean that either different amount of iodine was placed in the spotting tiles or different amounts of the starch and amylase solution was placed in the iodine, this was because it was difficult to measure out the same amounts of the iodine and starch and amylase solution.
My results could also be unreliable as in this investigation it was hard to keep it a fair test as it was difficult to keep things the same as it was hard to get same amount of iodine out of the pipette each time and to get the same amounts or anything from the amylase and starch solution into the iodine using a glass rod.
Changes.
I think a better way of doing the experiment would be by making a few adjustments:
The first thing I would change would be to repeat the investigation a third time. I think even though I repeated the experiment a second time, a third time would give a more accurate reading, so there wouldn’t be a plot of the curve on the graph.
The next thing I would change would be to find a more accurate way of placing the iodine and the starch and amylase solution in the spotting tiles. Again I think that this would give the affect of more reliable and accurate results, while also making it more of a fair test.
I would find a more accurate way of recording the time taken for all the starch to be broken down; maybe by using a digital stop clock. This I think would give more accurate results as the timing for the rate of reaction would be more accurate.
Further Investigations.
A further investigation I that I would carry out would be similar to this one, however instead of investigating the effect of temperature on enzymes, I would investigate the effect of pH on enzymes.
I would carry out the investigation at five different pH values to make it a fair test. The values would probably be different values on the pH scale, two acidic values, two alkaline values and neutral. Similarly to this investigation I would put the amylase at the different pH values for five minutes then I would add the starch and using iodine time how long it would take for the iodine to return to its original colour, which would tell me that the starch had been broken down completely. Then I would repeat the investigation at each of the pH values a second time.
I think my prediction for this investigation would be that the fastest rate of reaction would be for the neutral pH as enzymes work best at a certain pH around neutral. If the pH is to acidic or to alkaline the enzyme would become denatured.
Conclusion.
In conclusion, from this experiment it can be seen that temperature effects enzymes after it’s reached a certain temperature it causes the enzymes to become more and more denatured, this causes the rate to drop until the enzyme becomes totally denatured and stops working. Therefore it can be seen that enzymes only work at a certain temperature around 40oc, any higher the enzymes will become denatured or any lower and the enzyme is inactive.
Victoria Wright 10t
