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How to measure the rate of a chemical reaction catalysed by an enzyme and then how I can change the rate at which the enzyme speeds up the chemical reaction.

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Introduction

Biology coursework: GCSE I am going to investigate how to measure the rate of a chemical reaction catalysed by an enzyme and then how I can change the rate at which the enzyme speeds up the chemical reaction. The reaction I am going to investigate is Hydrogen Peroxide --> Water + Oxygen 2H20 --> 2H20 + 02 Catalyse is an enzyme found in all living cells. It causes Hydrogen peroxide to decompose into water (H20) and oxygen (02). Enzymes are able to increase the rate of a chemical reaction without being used up in the process. Enzymes are very efficient and small amounts at low temperatures can produce results that would usually require high temperatures and violent reactions. Increases in temperature can speed up the reaction; however enzymes become unstable when heated. Different factors that affect the speed of a chemical reaction that is catalysed by an enzyme are: Temperature When the temperature is increased the particles move faster as they have more energy. This results in more collisions, and the particles collide with higher energy, therefore the reaction is quicker. Heat can sometimes cause an enzyme to become out of shape, causing the substrate to no longer fit into the active site. Concentration If the solution is more concentrated it means there are more particles of reactant between water molecules. This makes collisions between important particles more likely to happen. ...read more.

Middle

Equipment * Washing up bowl half full of water * Large measuring cylinder * Two small measuring cylinders * A conical flask with a bung * Delivery tube * Stop watch * Goggles * 10cm3 hydrogen peroxide * 5cm3 enzyme Diagram Method 1. Fill the large measuring cylinder with water and invert it into the washing up bowl 2. Measure out 10cm3 hydrogen peroxide and pour into the conical flask 3. Using a clean measuring cylinder, measure out 5cm3 enzyme 4. Place the delivery tube so that one end of it goes up into the large measuring cylinder 5. Pour the enzyme into the conical flask with the hydrogen peroxide and immediately place on the bung and start the stop watch 6. Time for one minute and take a reading of the amount of gas in the large measuring cylinder Results Experiment 1 2 3 Strength of hydrogen peroxide (%) 100% 100% 100% Time (mins) 1 1 1 Measurement of gas (cm3) 95 97 91 Average 94.3 cm3 of gas I am now going to repeat the experiment although this time I will change the concentration of the hydrogen peroxide. I expect that the stronger the hydrogen peroxide is, the more gas will be collected in the large measuring cylinder. This is because as the concentration of substrate is increased, there are more hydrogen peroxide molecules available to fill the active sites and react. ...read more.

Conclusion

It is important to check that results are reliable because they make the experiment accurate. I feel that my results are reliable as took many precautions to ensure the reliability and fair tests of my experiments and there are no results that do not fit in with the line of best fit on my graph. I have collected sufficient results to make a firm conclusion that the stronger the concentration of the substrate, the quicker the reaction will take place when catalysed by an enzyme. Another way to investigate the effect of concentration on the rate of a reaction that is catalysed by an enzyme: 1. Set up apparatus as in the following diagram 2. Record the weight of the empty conical flask 3. Pour 5cm3 catalyse enzyme into the conical flask and record the weight of it minus the weight of the conical flask 4. Weigh the hydrogen peroxide and record the weight of it separately 5. Work out the sum of the hydrogen peroxide and catalyse to get the total weight of them added together in one conical flask 6. Pour the enzyme into the conical flask containing hydrogen peroxide whilst it is on the scales and start the stopwatch immediately 7. Time 1 minute and record the weight 8. Minus this from the total weight to calculate the weight of gas that has escaped during the reaction 9. Repeat the experiment with hydrogen peroxide at different concentrations A problem with this experiment is that very accurate weighing scales are needed to gain a reliable set of results. ...read more.

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