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Investigation to find out the rate of reaction when the concentration of Enzyme is changed.

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Introduction

Daniel Evans Investigation to find out the rate of reaction when the concentration of Enzyme is changed Hypothesis I predict that the rate of reaction will increase to a certain point were it is limited by the amount of substrate which is H2O2. Scientific Background on Enzymes An enzyme is a biological catalyst that will speed up the reaction without taking place in the reaction. Metabolic reactions are taken place all over your body and enzymes control most of these. They are very effective in the digestive system as they help to breakdown the different types of food substrates for example proteins are broken by protease into amino acids. Enzymes have a specific job certain enzymes break down molecules they are called catabolic enzymes and there are enzymes which put molecules together are called anabolic enzymes. The Lock and Key theory Enzymes have are specific and they have a cavity with a specific shape called the active site. The active site is the exact shape to fit the substrate, the active site being the key the substrate being the lock. The substrate binds to the enzyme and the reactions takes place immediately. The lock and key reactions are metabolic meaning that they are anabolic and catabolic. A catabolic reaction (the substrate has been broken down to form products) 1. The starch substrate is about to enter the amylase enzyme. The substrate fits exactly into the enzymes active site. 2. The substrate molecule slots into the active site and is tweaked changing its shape. 3. The starch molecule is split into maltose molecules; the enzyme is not changed in this process and will carry out this process over and over again. ...read more.

Middle

10 5 20 11 30 18 We can see that using 1cm diameter potato discs did not produce much oxygen and so I opted to use 0.5cm diameter which produced a lot more oxygen producing improving my final results in the investigation as it produced a larger surface area meaning that more potato was exposed to the hydrogen peroxide increasing the rate of reaction. We felt that the amount of hydrogen peroxide was efficient and did not need to be changed. We also used in the preliminary work a separating funnel to release the hydrogen peroxide into the conical flask with the potato discs but I found that this was very slow in releasing it and oxygen was probably lost as it was not totally air tight so I chose to use a 20 ml syringe as this would input the hydrogen peroxide a lot faster and use a stopper as no or less oxygen would be lost due to human error. My Investigation Apparatus Hydrogen peroxide Potatoes Knife Cork borer Glass syringe Stand with clamp 20ml Plastic syringe Side-arm Conical flask Stop clock Rubber stopper Weighing scales White tile Diagram Method 1. Peel the potato with the knife carefully, then insert the cork borer into the potato and extract the potato cylinder and cut it into discs of 5mm diameter on a white tile. 2. Set the apparatus as shown without adding the contents shown in conical flask and without putting the cork. 3. Withdraw 20ml of hydrogen peroxide with a different plastic syringe. 4. Measure 10 discs of potato. 5. Add the 10 discs of potato to conical flask but do not put the cork on yet. ...read more.

Conclusion

I feel computer data logging would have been useful as this could have took accurate readings of how much was given off simultaneously with the time and this would have made the results more accurate. Obviously repeating the experiment many more time would have improved our results but once again there was not enough time to do this. Further investigation I feel that for my further investigation I would carry on the same investigation but continue increasing the concentration using the same equipment, same size cork borer and same amount of hydrogen peroxide. I will do this to see if the graph continues to level off to prove that the rate of reaction is limited by the amount of substrate. So do this for 70, 80, 90, 100, 110, 120 potato discs. I feel the results this further investigation will produce justify my hypothesis. * Peel the potato with the knife carefully, then insert the cork borer into the potato and extract the potato cylinder and cut it into discs of 5mm diameter on a white tile. Do 70 discs. * Set the apparatus as shown in the diagram of the previous experiment without adding the contents shown in conical flask and without putting the cork. * Withdraw 20ml of hydrogen peroxide with a different plastic syringe. * Measure the required amount of potato discs. * Add the discs of potato to conical flask but do not put the cork on yet. * When you have the stop clock ready add the 20ml of hydrogen peroxide and quickly cork the conical flask * Then record the result the reading on the glass syringe after 60 seconds. * Wash the conical flask thoroughly. * Repeat this method for 80, 90, 100, 110, 120 potato discs. ...read more.

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