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An Experiment to Investigate the The Factors Affecting The Rate at Which Starch is Broken Down into Maltose.

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Introduction

An Experiment to Investigate the The Factors Affecting The Rate at Which Starch is Broken Down into Maltose. * Ratio * Temperature * Moles * Concentration * Percentage * pH The variable that I have chosen is temperature, as it will have the best and most accurate results that could enable me to calculate the rate. Both the concentration and the percentage would not give me very varied results. Therefore I am going to keep them as constants, these will need to be controlled. I will do preliminary work to help me find the best volumes, concentrations, masses, temperature ranges etc. that I will use for my main experiment. Method I changed the factor ratio to enable me to get the results at a suitable speed in my real experiment. First of all I used the ratio 1:1 at the optimum temperature of 50C. Then I did the experiment again at the temperature of 50C but this time at a ratio of 1:2, starch:amylase. I then did the experiment at a ratio of 1:2, amylase:starch. I made a mixture of concentration 2ml3 to 4ml3 for the ratio 1:2. I heated up both the amylase and the starch separately then mixed them when they both got to there correct temperature. The temperature I used in the preliminary work was 50 C as I knew that it was roughly the optimum temperature. As soon as I mixed them I started the timer. ...read more.

Middle

Enzymes speed up this reaction by diverting, and therefore lowering, the activation energy of the chemical reactions. The enzyme called amylase brakes down the substrate called starch. Starch is broken down in to maltose. Amylase does this by the active site of the amylase locking on to the substrate, starch, as they are made to fit perfectly. When they connect, the amylase brakes down the starch molecules. Therefore, the more frequent the amylase molecules collide with the starch molecules the quicker the reaction takes place, so the quicker the starch is broken down This is called the lock and key theory. For the starch and amylase molecules to collide more frequently they must gain energy to move faster. The energy gained is supplied by heat. Heat energy is transferred to the starch and the amylase molecules; this is then converted into kinetic energy. That is why I predict that the higher the temperature is the higher the rate of reaction will be. I have also predicted that at 50 C the rate of reaction will start to decrease. I predicted this because I know that the enzyme amylase has an optimum temperature of roughly 50 C. Above 50 C the amylase molecules will start to denature, this is when the heat starts to change the shape of there active site, therefore making connection between the amylase and the starch molecules, which are denatured, impossible. Therefore only the unchanged molecules can connect with the starch molecules and successfully break them down. ...read more.

Conclusion

When the temperature is as high as 70 C-80 C there are not enough amylase molecules left, that are still in tact, to get any noticeable breakdown of starch within about 360 seconds. I predicted that the rate of reaction would be doubled for every 10 C rise in temperature. This is called the Q10 theory. This will be shown by the gradient of the graph, which should be equal to two. This will only be relevant until over 50 C where the change will occur. As this has happened my prediction was correct. Most of my results are perfect. However there is one result that is a bit off compared to the other results. This is the result for 20 C. This maybe because in all the other experiments I used a thermostatic water bath but as room temperature is roughly 20 C I did not use a water bath. This could have affected my result for 20 C as it may have been a few degrees below and the thermometers could have been slightly wrong. It could also be because I miss read the colour change of the iodine. It could also have been caused by the fact that I did the set of results last, on a different day to my other experiments when the weather may have been colder therefore bringing down the room temperature I may have miss read on the thermometers. I could have taken more results for each temperature. I could have taken results on a wider range of temperatures I could have used the same thermometers each time to make my results better. ...read more.

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