Yeast cells contain an enzyme, catalase, which catalyses the release of oxygen from the substrate hydrogen peroxide. You will investigate the effect of temperature on the activity of catalase in yeast suspension Y. You are provided with the materials shown in Table 1.1. Table 1.1 labelled contents hazard volume/cm³ Y 3.0% yeast suspension none 100 H 3.0% hydrogen peroxide solution irritant 20 If any of Y or H comes into contact with your skin, wash off immediately under cold water. It is recommended that you wear suitable eye protection.

1. (a)(i)Think about the hazards of using the materials in Table 1.1. State whether the risk of using hydrogen peroxide solution, H, is low, medium or high. Give a reason for your answer. risk reason[1]
2. (a)(ii)You will test the activity of catalase in yeast suspension Y at room temperature and at other temperatures up to a maximum of 70 °C. Use the thermometer to measure the temperature of the room. State the room temperature and the other temperatures you will use in your investigation. room temperature other temperatures[1]
3. (iii)Decide how you could determine the rate at which drops are released from the syringe. The method that you decide should take no longer than two minutes. State the measurements that you will need to make.[2]
4. (iv)Record your results in an appropriate table.[5]
5. (v)State the concentrations of hydrogen peroxide solution that the student could prepare to provide a suitable range for this investigation. Outline how these concentrations could be prepared from 5.0% hydrogen peroxide solution. concentrations how prepared[2]
6. (vi)The student standardised the volume and concentration of the catalase solution. State one other variable that would need to be standardised. Describe how this variable could be standardised. variable how standardised[1]
7. (b)(i)Plot a graph of the data in Table 1.2 on the grid in Fig. 1.3. Use a sharp pencil for drawing graphs.[4]
8. (ii)Use your graph to estimate the enzyme activity when the pH is 4.0. Show on your graph how you estimated this value. enzyme activity =[2]
9. (iii)Describe the trend in the results shown by your graph plotted on Fig. 1.3.[1]
10. (iv)Explain the effect of pH on this enzyme.[3]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.