Mung bean seeds contain an enzyme that is used to hydrolyse (break down) sucrose into reducing sugars. This enzyme is essential to provide the reducing sugars needed for the seeds to grow. When mung bean seeds are soaked in sucrose solution, some of this enzyme diffuses into the surrounding solution and hydrolyses the sucrose. enzyme from seeds sucrose glucose and fructose The apparatus was set up as shown in Fig. 1.1. [Figure 1.1] Samples of the sucrose solution were removed at 10 minutes (sample S1), at 15 minutes (sample S2) and at 30 minutes (sample S3) after adding the sucrose solution. You are required to: • make a serial dilution of 1.0% reducing sugar solution, R • carry out the Benedict's test on each concentration of reducing sugar • carry out the Benedict's test on S1, S2 and S3 • estimate the concentration of reducing sugar in S1, S2 and S3. You are provided with the materials shown in Table 1.1. [Table 1.1] It is recommended that you wear suitable eye protection. If Benedict's comes into contact with your skin, wash it off immediately under cold water.

1. (a)(i)State the temperature you will need to maintain in the water-bath to carry out the Benedict's test. temperature[1]
2. (a)(ii)Complete Fig. 1.2 by drawing as many extra beakers and arrows as you need to show how you will carry out your serial dilution. For each beaker: • state, under the beaker, the volume and concentration of the reducing sugar solution in the beaker that will be available for use in the investigation, after the serial dilution has been completed • use one arrow, with a label above the beaker, to show the volume and concentration of reducing sugar solution added to prepare the concentration of the reducing sugar solution in the beaker • use another arrow, with a label above the beaker, to show the volume of distilled water, W, added to prepare the concentration of reducing sugar solution in the beaker. The first part of Fig. 1.2 has been labelled for you. [Figure 1.2][3]
3. (a)(iii)State the volume of Benedict's solution and the volume of each of the concentrations of reducing sugar solution you will use for each test. volume of Benedict's solution volume of each concentration of reducing sugar solution[1]
4. (a)(iv)Record your results in an appropriate table.[4]
5. (a)(v)State the time taken for the appearance of the first colour change for S1, S2 and S3. S1 S2 S3[1]
6. (a)(vi)Complete Fig. 1.3 by: • labelling the position on the line of each of the percentage concentrations of reducing sugar solution shown in Fig. 1.2 • putting the labels S1, S2 and S3 on Fig. 1.3 to show an estimate of the concentrations of reducing sugar in S1, S2 and S3. [Figure 1.3][2]
7. (a)(vii)Sample S1 was removed from the sucrose solution 10 minutes after seeds had been added. Sample S2 was removed 15 minutes after the seeds had been added. Suggest an explanation for the difference in results for S1 and S2.[1]
8. (a)(viii)If the mung bean seeds are soaked in the sucrose solution for more than 30 minutes, the concentration of reducing sugar remains the same as S3. Use your knowledge of enzymes to explain this observation.[1]
9. (b)(i)State the name of the test for protein.[1]
10. (b)(ii)The student mixed 2cm³ of the water containing the protein with 5cm³ of 1% sucrose solution. After 30 minutes, reducing sugars were present. Describe how the student could have set up a suitable control for this experiment to provide evidence that hydrolysis of sucrose was due to an enzyme.[2]
11. (c)Draw a bar chart of the data in Table 1.2 on the grid in Fig. 1.5. Each bar should be separated for each species of plant. Use a sharp pencil for drawing bar charts. [Figure 1.5][4]

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