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Investigate factors which affect the work of enzymes. I will be investigating how the concentration of starch, affects the rate of reaction between starch and amylase.

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By Carla Hodgkins 11U 21st January 2004 Coursework Investigation Factors Affecting Enzymes Aim To investigate factors which affect the work of enzymes. I will be investigating how the concentration of starch, affects the rate of reaction between starch and amylase. Factors, which can affect enzymes * Temperature - enzymes work best at low temperatures (below 45oC). At high temperatures the enzyme molecules may become denatured. * PH - Changes in the PH, alter the state of ionisation of charged amino acids that may play a crucial role in substrate binding and/or the catalytic action itself. * Changes in starch concentration, (see below) * Changes in enzyme concentration, at a higher concentration there will be more enzymes to break down the substrate, therefore decreasing reaction times. Prediction I predict that as the concentration of starch increases the time it takes the amylase to break down the starch will also increase. When the substrate is at a low concentration, collisions between the enzyme and the substrate molecule are infrequent, therefore reaction rates are slow, e.g. with a low concentration of starch, it will collide less frequently with the amylase than in a higher concentration of solution. As you increase the substrate concentration, the reaction rate will also increase proportionally, this is due to the collisions between the enzyme and the substrate becoming more frequent. Once the enzymes reach the maximum concentration in which they can react, they remain at a steady speed. ...read more.


I will be varying the concentration of starch with a range of, 1%, 2%, 3%, 4% and 5%. This range will enable me to discover at which concentration the enzyme can no longer work at a faster speed, therefore remaining constant, which will increase the experiment time. In theory the 5% solution should take five times as long as the 1% concentration. To change the concentration of the starch, I will simply use the 5% concentration and dilute it with water for the necessary concentration, e.g. 2% will need, 4cm3 of starch and 6cm3 of water. Results table The first results table will show at what time the starch began to break down and then the final time in which the experiment took. This will be done for all concentrations, and all three experiments, which were carried out. Key B = black DB = dark brown O = orange Concentration Exp 1 Exp 2 Exp 3 1% 0 sec B 0 sec B 0 sec B 10 sec DB 20 sec DB 20 DB 60 sec O 80sec O 60 sec O 2% 0 sec B 0 sec B 0 sec B 30 sec DB 20 sec O 30 sec 130 sec O 110 sec O 140 sec O 3% 0 sec B 0 sec B 0 sec B 40 sec DB 60 sec DB 60 sec DB 220 sec O 230 sec O 250 sec O 4% 0 sec B 0 sec B 0 sec B 100 sec DB ...read more.


Evaluation I think that the experiments went really well, with all but one result proving to be correct, and agreeing completely with the science related to the investigation. Although we could not get an exact measurement of the time, to the last second, it was very close, and as accurate as we could make it. Our results were in-between 10 seconds, e.g. between 60-70 seconds. However it was impossible to be able to test the solution every second, so these results were the closest we could get to the truth. To begin with we were only going to test the solution every 30 seconds as it says in the plan, however we soon realised that this was too much of a gap, as the colour of the iodine was changing to quickly. Some results may have been affected by the room temperature, as the experiments were carried out over a number of days, therefore room temperature had changed, and could have slightly affected the results. If I were to carry out the experiment again, I would measure the temperature of the room, and try to get it near enough the same every time we did an experiment. Therefore ensuring that this would not be an issue. There is enough substantial evidence, to support the conclusion, and to use as being scientifically proven. By doing each experiment three times, we ensured that our results were substantial, and were able to notice if something had gone wrong, to be able to eliminate that result, from the conclusion. ...read more.

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