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Investigating how enzyme concentration affects the rate of an enzyme reaction.

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Investigating how enzyme concentration affects the rate of an enzyme reaction. Introduction Hydrogen peroxide will breakdown into its products, oxygen and water, in the presence of Catalase. The rate of the reaction will increase with increasing enzyme concentration when molecules of hydrogen peroxide are freely available. However, when molecules of the substrate are in short supply, the increase in rate of reaction is limited and will have little effect. Hypothesis - Provided there is an excess substrate, an increase in enzyme concentration will lead to a corresponding increase in rate of reaction. Apparatus * Delivery Tube * Bungs * Test tubes * Test tube rack * Hydrogen peroxide * Catalase * Stop clock * pipettes Method 1. I will fill a 25cm3 measuring cylinder to the brim with water. I will then fill a 1000cm3 beaker with water. Taking care to keep the measuring cylinder full of water, I will invert it and place it in the beaker so that the mouth of the measuring cylinder is below the water surface. 2. I will take the delivery tube and place one end under the lip of the measuring cylinder. The end with the bung will be placed in the boiling tube. 3. I will set up the boiling tube in the test tube rack. 4. ...read more.


However, when molecules of the substrate are in short supply, the increase in rate of reaction is limited". The reasons for this are that there are number of variables that influence the decomposition of hydrogen peroxide in the presence of Catalase. Some of which can be classified as limiting factors i.e. the reaction is dependant or "limited" by their availability, to be able to function effectively; these include enzyme concentration, temperature and substrate concentration. All of these factors are required for an efficient reaction to take place, even when one is freely available the reaction can still be limited by the availability of the others. When I increased the enzyme concentration, it meant that there were more free active sites for the substrate molecules so that a greater quantity of substrate molecules could be broken down into products quicker. However past a certain point, which in my investigation was at an enzyme concentration 100% at time 4.5 minutes, there were many free active sites but insufficient substrate molecules to occupy them. Increasing the enzyme concentration further without increasing the substrate concentration will have no effect on the rate of reaction, which will eventually remain constant. When the enzyme catalase converted the substrate molecules into oxygen another molecule was produced, water. ...read more.


These may have occurred in either the measurement of the quantities of the enzyme. Another possibility was that changes in room temperature caused the rate of reaction to increase or the gas inside the boiling tube to expand, forcing more oxygen bubbles up the tube. Although minimal contact was made with the apparatus during the investigation, slight undetected variations in the room temperature may have led to inaccuracies. All the other possible causes are discussed above. The shape of the graph is as I predicted showing that as enzyme concentration increases so does the rate of reaction. This is because at a greater enzyme concentration, there are more free active sites available for the substrate and so more products can be made in a shorter length of time. However, it is not possible to take precise readings from the graph between the plotted points since insufficient readings were taken. To be able to do this, intermediate enzyme concentrations would have to be measured so that the shape of the graph would be more exact. Because the amount of hydrogen peroxide is the same in all five reactions, the total amount of oxygen eventually produced will be the same. For further work I will test this theory out by carrying the investigation until no more oxygen gas is produced. By Shayon McClements Page:3 ...read more.

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