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An experiment to show the varying rate of reactions when different concentrations of starch are broken down by the enzyme, amylase.

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Introduction

An experiment to show the varying rate of reactions when different concentrations of starch are broken down by the enzyme, amylase. Planning: Background information: Enzymes are biological catalysts that help break down large molecules into smaller molecules so that they are soluble without getting used up themselves. For this investigation I am going to investigate the effect of the concentration of a substrate, in this case starch, on the time taken for the enzyme amylase, to fully breakdown the substrate. The reason why these have to be used together is because each enzyme is designed specifically to break down only one substrate as each enzyme is made of a protein that causes it to be a specific shape, in this case the enzyme amylase can only break down starch to maltose. This is called the lock and key theory. Concentration affects the rate of reaction in substances. If the concentration is high, there is more of chance of successful collision; however this also means it will take longer to react as there is more to break down. If there is a low concentration, there is less chance of successful collision, but the particles that do collide will make the reaction faster. N.B: There is the same amount of amylase in both diagrams. - Amylase - Starch There is more chance of successful collision in this case, but as there is more starch to be broken down, the reaction will be slower. (High starch concentration) There is less chance of successful collision in this diagram, but as there is less starch than there is amylase therefore less to be broken down, they will react together faster. ...read more.

Middle

I will repeat each experiment thrice to check accuracy and reliability. If my measurements of the reaction time at any concentration don't agree, I will carry on repeating the experiment to see whether I can reject any odd results or not. Apparatus: 1 Spotting tile 3 syringes 1 graduated pipette Iodine solution 2% starch solution 0.2% amylase solution Water Thermometer (to ensure the experiment was held at room temperature) 4 beakers Test tube rack 1 test tube Method: Firstly I will measure out the volumes of the stock solutions from starch and amylase, and amylase will always be 5ml so that any pattern seen can be said to be due to the starch, and not any other factor. In order to make it a fair test, all variables apart from the concentration of starch were kept the same, i.e. the amylase was kept at 5ml at all times, all experiments were carried out at room temperature and the volume of solution was kept constant too. I will do in total, 6 experiments: 5ml starch and 0ml water, 4ml starch and 1ml water, 3ml starch and 2ml water, 2ml starch and 3ml water, 1ml starch and 4ml water, 0ml starch and 5ml water. The reason for using six different concentrations of starch was to give a more accurate pattern of results. The range of concentrations used is 0% to 100%. This spread will provide enough results to show the relationship between the concentration of starch and the rate of reaction. To ensure accurate and reliable results are obtained, the experiments will be repeated three times and an average of those will be taken. ...read more.

Conclusion

therefore, the time taken to breakdown all the substrates increases as you increase substrate concentration. My results support this scientific knowledge and prediction. Evaluation: This investigation was fairly simple and safe to carry out and it did provide me with accurate and reliable results. I know that my results were reliable since the results of the repeated experiments were close to those of the original experiments. I used the average of the three results to obtain a more accurate pattern in my results. My results were fairly accurate, but they could have been more accurate with less human error. Deciding when to start the timer, the number of times I stirred the amylase and starch solution, and deciding when to stop the timer could all have led to inaccuracy of results. As you can see from my two rough graphs, I did have 3 anomalous readings in my results altogether. These results did not fit my line of best fit so I repeated the appropriate experiments until all the crosses fit the line of best fit. The experiment was safe to conduct since I used safety goggles to protect my eyes from any harmful substances, and I wore a lab coat to avoid spoiling my clothes by spilling substances on them. If I were to carry out the experiment again, I would use a wider range of concentrations of starch so that any pattern that emerges will become more evident. In order to provide additional relevant evidence, I could vary the amylase concentrations as well as starch concentrations as this would remove the limiting factor. I would then have a wider range of reaction times to analyse. Meena Jassal 11J ...read more.

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