CAIE Biology (9700)

Dialysis tubing is a partially permeable membrane. Glucose molecules can dif fuse through the dialysis tubing. You are required to investigate the dif fusion of glucose across dialysis tubing. You are provided with the materials shown in Table 1.1. Table 1.1 labelled contents hazard volume / cm G 20.0% glucose solution low 50 W distilled water low 200 Benedict'sBenedict's solution harmful irritant 40 length of dialysis tubing in distilled water low - If any solution comes into contact with your skin, wash of f immediately with cold water . It is recommended that you wear suitable eye protection. You will need to: Carry out step 1 to step 11. step 1 Draw a mark 8 cm from the top of a large test-tube, as shown in Fig. 1.1. mark 8 cm from the top 8 cm step 2 Remove the dialysis tubing from beaker D. Tie a knot in the dialysis tubing as close as possible to one end, so that the end is sealed. step 3 The whole length of the dialysis tubing needs to be separated to allow the tubing to be filled with solution. To do this, rub the whole length gently between your finger and thumb. step 4 Put 10 cm of 20.0% glucose solution, G, into the open end of the dialysis tubing. step 5 Rinse the outside of the dialysis tubing by dipping it in the water in beaker D. step 6 Put the dialysis tubing containing G into the large test-tube and keep it in position using an elastic band as shown in Fig. 1.2. mark on test-tube knot dialysis tubing large test-tube 10 cm of glucose solution elastic band Fig. 1.2 * 0000800000003 * step 7 Put distilled water into the large test-tube so that the top of the water is above the level of the glucose solution in the dialysis tubing. step 8 Start timing. You are required to take samples of the water surrounding the dialysis tubing every 5 minutes for 15 minutes. You will collect three samples. step 9 Label three test-tubes with the times the samples of water will be taken (5, 10 and 15). step 10 After 5 minutes (step 8), put a 1 cm syringe into the water surrounding the dialysis tubing so that the end of the syringe is level with the mark on the test-tube. Remove 1 cm from the water surrounding the dialysis tubing and put this into the test-tube labelled 5. Repeat this action to remove another 1 cm from the water surrounding the dialysis tubing and put this into the test-tube labelled 5. The test-tube labelled 5 will now contain a 2 cm sample. Do not stop timing. step 11 Repeat step 10 at 10 minutes and at 15 minutes using the appropriately labelled test-tubes. You need to carry out a dilution of the 20.0% glucose solution, G, to make a 1.0% glucose solution. You will need 20 cm of this 1.0% glucose solution.

(i) Complete Table 1.2 to show the volume of distilled water , W, you will use to make 20 cm of a 1.0% glucose solution. Table 1.2 volume of 20.0% glucose solution, G / cm volume of distilled water, W / cm [1] step 12 Prepare the 1.0% glucose solution as shown in Table 1.2. You will need to carry out a serial dilution of the 1.0% glucose solution you have prepared in step 12 as shown in Fig. 1.3. You must reduce the concentration by half between each successive dilution. You will need to prepare four concentrations of glucose solution in addition to the 1.0% glucose solution from step 12. After the serial dilution is completed, you will need to have 10 cm of each concentration available to use. * 0000800000004 *

Complete Fig. 1.3 to show how you will prepare your serial dilution. Each beaker should have: 1.0% glucose solution 0.5% glucose solution 0.25% glucose solution 0.125% glucose solution 0.0625% glucose solution [2] * 0000800000005 * step 13 Set up a boiling water-bath ready for step 18 and step 22. step 14 Prepare the concentrations of glucose solution as shown in Fig. 1.3. step 15 Label 5 test-tubes with the concentrations of glucose solution shown in Fig. 1.3. step 16 Put 2 cm of the 1.0% glucose solution into the appropriately labelled test-tube.

You are required to carry out the Benedict' s test on the glucose solutions that you have prepared in step 14. State the volume of Benedict' s solution you will use for each reducing sugar test. Explain why you have selected this volume. volume of Benedict's solution cm explanation [1] step 17 Put the volume of Benedict' s solution stated in (a)(iii) into the test-tube labelled 1.0%. Shake gently to mix. step 18 Put this test-tube into the boiling water-bath and record in Table 1.3 the time to the first colour change. If there is no colour change after 120 seconds, stop timing and record the time as 'more than 120'. step 19 Remove the test-tube from the boiling water-bath. step 20 Repeat step 16 to step 19 using 2 cm of each of the other concentrations of glucose solution.

Complete Table 1.3 to record your results. Table 1.3 percentage concentration of glucose 1.0 0.5 0.25 0.125 0.0625 [1] * 0000800000006 * Y ou are required to carry out the Benedict' s test on the three samples collected from the water surrounding the dialysis tubing (5, 10 and 15). step 21 Put the volume of Benedict' s solution stated in

the time to the first colour change. If there is no colour change after 120 seconds, stop timing and record the time as 'more than 120'. step 23 Remove the test-tube from the boiling water-bath. step 24 Repeat step 21 to step 23 for the other samples (10 and 15).

Record your results in an appropriate table.

State one source of error when carrying out the Benedict's test.

Use your results in

to estimate the percentage concentration of glucose in the samples taken at 5, 10 and 15 minutes. percentage concentration of glucose in sample 5 = percentage concentration of glucose in sample 10 = percentage concentration of glucose in sample 15 = [1] * 0000800000007 *

Suggest a reason for the percentage concentrations of glucose estimated in (a)(vii). Question 1 continues on page 10. * 0000800000009 *

A dialysis membrane, similar to dialysis tubing, is used in the treatment of kidney disease. During this treatment, the blood of a person with kidney disease is passed through a dialysis machine to remove unwanted waste products from the blood. The machine contains dialysate which is a solution of glucose and ions. Blood flows through the dialysis machine and is separated from the dialysate by a membrane. Some molecules diffuse from the blood into the dialysate. This is shown in Fig. 1.4. blood from person with kidney disease molecules diffusing into the dialysate dialysate (solution of glucose and ions) dialysis membrane separates the blood from the dialysate Scientists studied the movement of two molecules, P and Q, found in the blood of a person with kidney disease. They wanted to see if these two molecules would remain in the blood or move out of the blood across the dialysis membrane into the dialysate. The scientists took samples of blood from a person using a dialysis machine every 5 minutes for 20 minutes and recorded the concentration of P and Q in these samples. The results are shown in Table 1.4. Table 1.4 time sample was taken from the blood / min concentration of P in the blood / arbitrary units concentration of Q in the blood / arbitrary units 0 200 400 5 205 280 10 200 150 15 195 90 20 200 75 * 0000800000010 *

Plot a line graph of the data in Table 1.4 on the grid in Fig. 1.5. Use a sharp pencil. [4] * 0000800000011 *

Calculate the percentage decrease in concentration of Q between 5 minutes and 20 minutes. Show your working and give your answer to two significant figures.

Suggest a reason for the rate of decrease in the concentration of Q from 0 to 10 minutes and from 10 to 20 minutes. 0 to 10 minutes 10 to 20 minutes [2] [Total: 20] * 0000800000012 * Question 2 starts on page 14. * 0000800000013 *

K1 is a slide of a stained transverse section through a root.

(i) Draw a large plan diagram of the region on K1 indicated by the shaded area in Fig. 2.1. Use a sharp pencil. Use one ruled label line and the label T to identify a tissue involved in transport of substances throughout the plant. draw this region [5] * 0000800000014 *

Observe the cells in the centre of the root on K1. Select a group of four adjacent cells. Each cell must touch at least one of the other cells. Make a large drawing of this group of four cells. [4] * 0000800000015 *

Fig. 2.2 is a photomicrograph of a stained transverse section through the root of a dif ferent plant to K1. One dif ference between the section in Fig. 2.2 and the section on K1 has been labelled. Identify three other observable dif ferences between the section in Fig. 2.2 and the section on K1. Draw three label lines on Fig. 2.2 to label the three dif ferences you have identified. You should complete the labels to describe the differences you observe. The width of the cortex tissue is smaller in Fig. 2.2 than on K1 magnification ×35 [4] * 0000800000016 *

A student was asked to find the area of the vascular tissue in a transverse section of root. The student grew one plant for three weeks and took a section from one of the roots. This section is shown in Fig. 2.3. magnification ×35 The vascular tissue is the central region of the section. Assume that the vascular tissue is a circle. The line A-B is the diameter of the vascular tissue.

Calculate the actual area of the vascular tissue. Use the formula: area = πr , where π = 3.14. actual area of the vascular tissue = mm [4] * 0000800000017 *

The student wrote a hypothesis which stated that: The area of vascular tissue in a root section changes as the plant grows. Suggest modifications to the method used in

to investigate this hypothesis. [Total: 20] * 0000800000018 * BLANK PAGE * 0000800000019 * Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable ef fort 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. BLANK PAGE * 0000800000020 *