Enzyme E hydrolyses (breaks down) starch to reducing sugar. You are required to investigate the effect of temperature (independent variable) on the activity of E by recording the time taken for the starch to be hydrolysed (dependent variable). (a) You will investigate the hydrolysis of starch: • at room temperature • at other temperatures, starting at 40°C to a maximum of 80 °C. You are provided with: labelled | contents | hazard | volume/cm³ E | 2.0% enzyme E solution | harmful | 20 S | starch solution | none | 50 iodine | iodine solution | none | 15 You are advised to wear suitable eye protection. Iodine solution is a stain. If E or iodine comes into contact with your skin, wash it off immediately under cold water. The enzyme and starch solutions are mixed together and then a sample of the mixture is removed every 15 seconds and tested for starch. The end-point of the hydrolysis of the starch is when a sample does not change the colour of iodine solution, showing that all of the starch has been hydrolysed.

1. (a)(i)State the temperatures, other than room temperature, that you will investigate.[2]
2. (a)(ii)Record your raw results by completing Table 1.1, using the letters stated below for the colours. You will observe a range of colours depending on the concentration of starch in the sample. You will see some of the following colours and should record the colours by using these letters. BB blue/black DP dark purple P purple PP pale purple DB dark brown B brown PB pale brown Y yellow/orange (colour of iodine solution at start) Table 1.1 colour of iodine solution time/s 15 30 45 60 75 90 105 120 135 150 165 180 temperature/°C[3]
3. (a)(iii)Prepare the space below and, using your raw results from Table 1.1 in (a)(ii), record the time taken for enzyme E to hydrolyse all of the starch at each temperature. Record 'more than 180' if there is still starch present at 180 seconds.[4]
4. (a)(iv)Describe two significant sources of error in this investigation.[2]
5. (a)(v)A student using the same enzyme concluded that the source of enzyme E was not from humans. Explain how your results support the student's conclusion.[2]
6. (a)(vi)This procedure investigated the effect of temperature on the activity of enzyme E, using the time taken to hydrolyse starch. To modify this procedure for investigating another variable, temperature (the previous independent variable) would need to be standardised. Describe how the temperature could be standardised. Think about how you could modify this procedure to investigate the effect of enzyme concentration (the new independent variable) on the time taken to hydrolyse the starch. Describe the modifications needed to investigate the effect of enzyme concentration.[3]
7. (b)(i)Use a sharp pencil for graphs. Plot a graph of the data shown in Table 1.2.[4]
8. (b)(ii)Describe the effect of temperature on the activity of this enzyme.[1]

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