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The effect of a competitive inhibitor on the rate of reaction.

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Coursework The effect of an competitive inhibitor on the rate of reaction Nature of the problem There have been many problems with pollution, which have affected agriculture. An example of this is pollution from coal mines in area such as Sheffield. Ions such as copper, leak from the mines into the soil in nearby fields. These fields are used to grow crops on. When leaching of metal ions occur from coalmines it can affect crops growing in near by fields. The ions get into the soil and affect the growth of the crop by acting as inhibitors and not allowing enzyme substrate complexes to form; an example of this is what will be investigated in the investigation - copper II sulphate ions leach from the coalmines and get into the soil affecting the rate at which the catalase in celery is broken down. In the case of catalase the active site is the haem group. Competitive inhibition occurs because the inhibitor has a similar shape to the substrate, and due to the 'lock and key' theory can bind to the active site. Copper sulphate is a competitive inhibitor of catalase. Enzymes are proteins which are responsible for catalysing almost every metabolic reaction which can occur in living organisms. Most enzymes catalyse only one type of reaction, so each living organism requires thousands of different enzymes. ...read more.


As temperature increases so does the rate of reaction. This is because by increasing the temperature, the molecules have more kinetic energy, therefore they collide more frequently, forming more enzyme-substrate complexes. However once the optimum pH is reached, the rate of reaction begins to decrease as above this value, the shape of the active site is altered. This is because the high temperatures cause hydrogen bonds holding the active site in shape to break. An alteration in the shape of the active site means that the enzyme and substrate are no longer complementary so fewer and fewer enzyme-substrate complexes are formed Temperatures above 40-50�C denature many enzymes.. pH is measured on a scale of 0-14. Values below 7 are acidic, values above 7 alkaline and a value around 7 is neutral. As the pH moves into the acidic range the enzyme tends to gain hydrogen ions from the solution. As the pH moves into the alkaline range the enzyme tends to lose hydrogen ions to the solution. In both cases the changes in pH cause the charge on the R-group of the active site to change, denaturing the enzyme. If all other conditions are held constant, the rate of the reaction should increase with increasing concentrations of substrate. At very low values of substrate the reaction rate will increase very rapidly. ...read more.


The temperature will be kept the same (ROOM TEMPERATURE) as if this is not controlled, it will affect the rate at which the enzyme works and will produce unreliable results, as a result the solution will be kept in a thermo regulated water bath for 5 minutes and all of the procedures, will be carried out in the same room on the same day. The amount of substrate, hydrogen peroxide, will be kept the same at 10cm�, as by altering the rate of reaction will change, as concentration of substrate affects enzyme activity. The pH also affects enzyme activity, so it must be the same (ph7) for all solutions. This can be controlled by buffering the solutions and checking their pH to make sure they are all the same. OUTLINE METHOD APPARATUS materials * Glass syringe ( cm� ), this will be used to measure the volume of oxygen produced. It allows the volume to be read accurately to 1d.p. Collecting the volume of gas this way is more accurate and reliable than counting the number of bubbles produced in a boiling tube, which would be the alternate method. * Conical flask, this will be used to put the hydrogen peroxide, copper(II) sulphate and celery solution into, as it provides a large for the substrate and enzyme to work in. ...read more.

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