Biology 2023 · Oct/Nov

in sucrose solution. Carry out step 10 to step 20. step 10 Label five beakers 1, 2, 4, 8 and 16 and label five test-tubes 1, 2, 4, 8 and 16. step 11 Put 1, 2, 4, 8 or 16 beads into each of the appropriately labelled beakers, as shown in Fig. 1.3. yeast bead 1 2 4 8 16 step 12 Put 10 cm of sucrose solution, S, into each of the beakers containing the beads. step 13 Start timing and leave for 5 minutes. While you are waiting set up a water-bath ready for step 14 and step 19. In step 19 you will use the water-bath to carry out the test for reducing sugars using Benedict's solution, B.

State the temperature you will use for the water-bath. temperature [1] step 14 Heat the water-bath to the temperature stated in

and time how long before the appearance of the first colour change. If there is no colour change after 2 minutes, stop timing and record as 'more than 120'. Record your result in

Record your results in an appropriate table.

State the independent variable in this investigation.

State one main source of error in this investigation.

A student set up a beaker as a control experiment. The result of the control experiment showed that the sucrose was hydrolysed by an enzyme. Suggest what substances the student put in the beaker for the control experiment.

The procedure described in step 1 to step 20 investigated the effect of changing the number of yeast beads on the rate of hydrolysis of sucrose. Describe how you would modify the procedure to investigate the effect of changing the concentration of the sucrose solution on the rate of hydrolysis of sucrose.

Pectinases are enzymes that are used to increase the volume of fruit juice extracted from apples. Pectinases can be immobilised and placed inside a container with apple pulp as shown in Fig. 1.4. The fruit juice is then collected. fruit juice apple pulp immobilised pectinase A scientist carried out an investigation to determine the effect of temperature on the activity of immobilised pectinase by measuring the volume of fruit juice extracted. All other variables were kept constant. The results are shown in Table 1.2. Table 1.2 immobilised pectinase temperature / °C volume of fruit juice / cm 30 38 40 54 50 79 60 98 70 62 80 4

Plot a graph of the data in Table 1.2 on the grid in Fig. 1.5. Use a sharp pencil.

Use your graph in Fig. 1.5 to estimate the volume of fruit juice extracted at 55 °C. Show on your graph how you obtained your answer. volume of fruit juice = cm

Describe the change in volume of fruit juice shown by your graph in Fig. 1.5. The scientist repeated the investigation replacing the immobilised pectinase with the same amount of pectinase but not immobilised in beads (free pectinase). The results are shown in Table 1.3. Table 1.3 free pectinase (not immobilised) temperature / °C volume of fruit juice / cm 30 52 40 85 50 98 60 41 70 12 80 4

Suggest an explanation for why more fruit juice was obtained when using the free pectinase between the temperatures of 30 °C and 50 °C than when using immobilised pectinase.

Suggest an explanation for why more fruit juice was obtained when using immobilised pectinase between the temperatures of 60 °C and 70 °C than when using the free pectinase. [Total: 22] 2 K1 is a slide of a stained transverse section through a plant leaf.

(i) Draw a large plan diagram of the whole leaf on K1. Use a sharp pencil. Use one ruled label line and label to identify the epidermis.

Observe the cells in the epidermis of the leaf on K1. Select a line of four adjacent epidermal cells. Each cell must touch at least one of the other epidermal cells. [5] Fig. 2.1 is a photomicrograph of a stained transverse section of a leaf from a different type of plant.

Identify three observable differences between the leaf on K1 and the leaf shown in Fig. 2.1. Record these three observable differences in an appropriate table. [4] Fig. 2.2 is an enlarged version of the transverse section of the leaf shown in Fig. 2.1.

(i) Measure line P and line Q to find the length of vascular bundle P and the length of vascular bundle Q as shown in Fig. 2.2. length of vascular bundle P = length of vascular bundle Q =

Calculate the percentage difference in length between vascular bundle P and vascular bundle Q. Show your working and give your answer to two significant figures. answer = % [2] [Total: 18] Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Local Examinations Syndicate (UCLES), which is a department of the University of Cambridge.