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Investigation of the effect of the pH value on the enzyme controlled reaction

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Investigation of the effect of the pH value on the enzyme controlled reaction Background ´┐ŻA buffer is a mixture of a weak acid and a soluble salt of that acid. It is used to maintain the pH value of a solution. A weak acid can dissociate in solution to form H ions and the acid group ions. The concentration of the H ions decides the pH value of the solution. The H ions and the weak acid molecules are at an equilibrium state. If either of them increases the concentration, the reaction will go towards the side at which the molecules or ions with low concentration. To insure the solution with an almost constant pH value, the little amount H ions or OH ions should be removed if they are added to this solution. ...read more.


Neither too many nor too little is good for the shape of the enzyme (depend on the type of the enzyme). An enzyme with the distorted shape will not fit the substrate well so lose the ability to catalyse the reaction. As pH value gets higher and higher, the H ions get more and more and fewer and fewer enzymes can work properly. In consequence the rate of reaction is lower and lower. Safety a). Goggles essential as the solution with pH value 5 is irritant b). Almost all the enzymes all potentially irritant so avoid contact with skin. Apparatus 2 x Goggles / 10 x test tube / 6 x 2ml syringes / marker pen / 2 x iodine solution in dropper bottle (full) / 2 x stop clocks / 4 x spotting tiles / 1x thermometer / 4 x glass rods /10 x tissues Access to Starch suspension(1.0%)-about 25ml per group ( for wastage) ...read more.


6.Repeat step 5 for each pair of starch and amylase, record the time for amylase to break down the starch. Results pH at which reaction took place Time taken for amylase to breakdown the starch / s Personal results / reciprocals Average class results / reciprocals Personal Time Reciprocal *1000 Class average Average reciprocal*1000 4.0 1080+ 0.9 809 1.2 4.8 943 1.1 6.0 429 2.3 7.7 40 25 65 15.3 8.9 120 8.3 129 7.8 Note: To time the Average reciprocal is simply to make the value easier to read. Graph plotted on the graph paper Interpretations The graph shows as the pH value increases from 0 to around 7.7, the rate of reaction increases. As pH value increases from 7.7 to further, the rate of reaction decreases. This shows that amylase has an optimum pH around 7.7 (neutral). The interfering of the enzyme by H ions is described in the background. ...read more.

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