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Changing the surface area - Making the surface area greater increases the chance of particles colliding.
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Catalysts - This is a substance, which alters the rate of reaction without being used up its self.
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Enzymes - An Enzyme is an example of a catalyst. Only each enzyme has a special shape, this causes each enzyme to be specific to a reaction.
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Changing the concentration - The higher the concentration the more particles there are within the same amount of space. This increases the chance of collisions.
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Changing the temperature - When the temperature is increased all the particles within vibrate which makes them collide more.
Denaturing: Protein denaturation is commonly defined as any noncovalent change in the structure of a protein. This change may alter the secondary, tertiary or quaternary structure of the molecules. When a protein is heated to temperatures over 50 degrees Celsius, the cross-linkages in its molecules break down; the protein molecules lose their shape and will usually not regain it even when cooled. The protein is said to be denatured. Because the shape of the molecules has been altered, the protein will have lost its original properties. When an enzyme is at use, it is at its best working. If we take the example of formula 1, a car in formula one runs at its limits and if it were to be pushed any further it would break down. It is the same case with Enzymes if they are heated too much they lose their shape, denature and they stop working.
Optimum temperature: The pH or temperature at which an enzyme works best is often called its optimum pH or temperature. An enzyme, which is inactivated by a low pH, will resume its normal activity when its optimum pH is restored. Extremes of pH, however, may denature some enzymes irreversibly.
Apparatus used: milk, renin, thermometer, test tubes, tripod, flame, beaker, flask, syringe, heatproof mat, safety goggles and a stop clock.
Method
- The substrate used in the experiment is milk and the enzyme used is renin.
- First, I filled 5ml of milk into a syringe and poured it into a test tube.
- I heated the milk to the particular temperature and measured it with a thermometer.
- Using another syringe, I filled 0.25ml of the enzyme (renin).
- When the milk reached the temperature, I put the enzyme into the test tube and started the stop clock.
- The objective was to stop the clock as soon as I found that the milk had clotted.
- When I found the milk had clotted I stopped the clock and recorded the time.
- I repeated this procedure five times to get my readings.
Fair Test: In order to ensure that this was a fair test I used the same amount of milk (5ml) and enzyme (.25ml) every time. The enzyme was only put into the milk when the temperature of the milk had reached exactly to what it was supposed to be, thus eliminating the chances of any faulty readings.
Results Table
Description of graph: At the beginning of the Graph we see the line(rate of reaction) steadily rising and later there is a fall. From around 10 degrees Celsius the rate of reaction increases thus more molecules collide. When it reaches around 45 degrees Celsius we see the line dropping suggesting the rate of the reaction is slowing down. This continues all the way to the bottom where the reaction stops.
Explanation of graph: As the temperature rises the rate of reaction increases. Which means that the molecules collide with each other more often. As the temperature rises more molecules collide thus helping to increase the rate of the reaction. However when the reaction reaches a certain stage it drops. This is due to the enzyme denaturing. When the enzyme denatures (loses its shape) the reaction stops, thus the fall. At temperatures up to 40 degrees Celsius the enzyme continues to function but after that it falls. This suggests that the optimum temperature is some where around 40 degrees Celsius.
Supporting the original prediction: My original prediction stated as the temperatures increases the rate of reaction would increase and when it would reach a certain temperature (around 40 – 45 degrees Celsius) it would slow down. This would be due to the denaturing of the enzyme. Looking at the results we can see that the prediction is correct.
Limitations: The experiment carried out did have a few limitations. The experiment had no fixed end point thus we do not know if the milk would ever clot since there is a possibility of it getting clotted after a very long time. In the experiment the milk was heated to a certain temperature whereas the enzyme was not. Thus if the enzyme were at the same temperature as the milk was while passing through its optimum temperature it could have clotted the milk instead of denaturing.
Improvements: The experiment could be improved further by recording more temperatures. Also if a pre test were carried out it would have been better as it could have confirmed the results I got and whether they were right or not. If even gaps between temperatures were taken the results would be even clearer and easy to understand.
Further Work: To do any further research on enzymes and confirm the results I obtained I could test other enzymes such as lipase, amylase or protease. After investigating these enzymes I could compare them to the results I got and further confirm my results.