The enzyme catalase catalyses the reaction shown in Fig. 1.1. catalase hydrogen peroxide → water + oxygen [Figure 1.1] A student had read that copper(II) sulfate can act as an inhibitor, reducing the activity of catalase. The student wanted to investigate the effect of copper(II) sulfate as an inhibitor on the activity of catalase to test the hypothesis: The higher the concentration of the inhibitor copper(II) sulfate, the lower the volume of oxygen produced in the presence of catalase.

1. (a)State the independent variable and dependent variable in this investigation. independent variable .................................................................................................................................................................. dependent variable ..................................................................................................................................................................[2]
2. (b)(i)The student was provided with a 0.04 moldm⁻³ solution of copper(II) sulfate. Describe how the student could use serial dilution to make a suitable range of concentrations to test their hypothesis.[2]
3. (b)(ii)The student used the apparatus shown in Fig. 1.2 to collect the data needed to test the effect of different concentrations of copper(II) sulfate on the production of oxygen in the presence of catalase. [Figure 1.2] Describe a method the student could use to collect the data needed to test the effect of different concentrations of copper(II) sulfate on the production of oxygen in the presence of catalase. The description of your method should be set out in a logical way and be detailed enough for another person to follow. You should not repeat the details from (b)(i) describing how to dilute the 0.04 mol dm⁻³ copper(II) sulfate solution or how to set up the apparatus shown in Fig. 1.2.[6]
4. (b)(iii)The hypothesis the student tested was: The higher the concentration of the inhibitor copper(II) sulfate, the lower the volume of oxygen produced in the presence of catalase. Complete Fig. 1.3 by: • adding axes labels and units • sketching a graph of the results you would expect if the hypothesis is correct. [Figure 1.3][3]
5. (c)(i)Draw on Fig. 1.4 to show how you could derive the Km value of catalase without copper(II) sulfate.[3]
6. (c)(ii)The student concluded that copper(II) sulfate was a non-competitive inhibitor of catalase. State the evidence in Fig. 1.4 that supports this conclusion.[2]

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