Cambridge A Level Biology 9700 — 2015 May/June Paper 3 · Variant 1

This document consists of 11 printed pages and 1 blank page. DC (NF/SW) 87479/3 © UCLES 2015 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level * 7 7 3 2 8 6 5 7 4 2 * BIOLOGY 9700/31 Advanced Practical Skills 1 May/June 2015 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. Electronic calculators may be used. You may lose marks if you do not show your working or if you do not use appropriate units. At the end of the examination, fasten all your work securely together. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 2 Total

2 9700/31/M/J/15 © UCLES 2015 Before you proceed, read carefully through the whole of Question 1 and Question 2. Plan the use of the two hours to make sure that you finish all the work that you would like to do. If you have enough time, consider how you can improve the accuracy of your results, for example by obtaining one or more additional measurements. You will gain marks for recording your results according to the instructions. 1 Starch is the substrate of enzyme E. When they are mixed, a reaction takes place and a biological molecule is produced, the product. You are required to investigate the effect of enzyme E on starch. You are provided with: labelled contents hazard S 1% starch solution none E enzyme solution harmful irritant W distilled water none iodine iodide solution harmful Benedict’s Benedict’s solution harmful Proceed as follows: 1. Set up a water-bath to heat to boiling (approximately 100 °C) ready for step 9. 2. Test a drop of solution S for starch and record your observations in (a)(i). 3. Put 3 cm3 of S into a test-tube. 4. Put 1 cm3 of E into the same test-tube. 5. Shake the test-tube gently to mix the contents. 6. Leave the test-tube for 5 minutes, shaking it occasionally. 7. After 5 minutes, test a drop of the mixture from the test-tube for starch and record your observations in (a)(i).

3 9700/31/M/J/15 © UCLES 2015 [Turn over (a) (i) Prepare the space below and record your observations. [3] The rate at which enzyme E catalyses a reaction with S can be investigated by measuring the rate at which the products of the reaction are produced. You are required to identify the type of biological molecule produced (the product) when S and E are mixed. 8. Put 4 cm3 of Benedict’s into the test-tube containing the mixture of S and E. This will inhibit enzyme E. 9. Put this test-tube into the boiling water-bath and immediately start timing. (ii) Record the time taken for the first appearance of any colour change. If there is no colour change after 180 seconds remove the test-tube from the water-bath and record your result. … [1] 10. Turn off the Bunsen burner. (iii) Explain the effect that enzyme E has on starch, using your observations from (a)(i) and the result from (a)(ii). … [1] (iv) Suggest the name of a biological molecule that could have been produced when S and enzyme E were mixed. … [1] When carrying out a practical procedure, the hazards of the use of all the apparatus and all of the reagents need to be considered, then the level of risk needs to be assessed as low or medium or high. (v) State the hazard with the greatest level of risk when carrying out steps 8 to 10. State the level of risk of the procedure: low or medium or high. hazard … level of risk … [1]

4 9700/31/M/J/15 © UCLES 2015 A student investigating the effect of enzyme E on starch suggested the hypothesis: “lowering the concentration of starch below 1% will have no effect on the rate at which the product is produced.” You are required to investigate this hypothesis by: • carrying out a serial dilution of S • investigating the effects of different concentrations of starch solution on the rate at which the product is produced. (b) (i) You are required to make a serial dilution of the 1% starch solution, S, which reduces the concentration of the starch solution by half between each successive dilution. You will need to prepare 20 cm3 of each concentration. You should use the beakers shown in Fig. 1.1 to show how you will prepare the serial dilutions. For each beaker, complete Fig. 1.1 to show how you will dilute the solution by: • stating, under the beaker, the concentration and volume of the starch solution available for use in the investigation • using one arrow, with a label above the beaker, to show the concentration and volume of starch solution added to prepare the concentration • using another arrow, with a label above the beaker, to show the volume of W added to prepare the concentration.

5 9700/31/M/J/15 © UCLES 2015 [Turn over … … … 10 cm3 1% 20 cm3 1% starch solution 10 cm3 1% starch solution 0 cm3 W starch solution to use … … … … … … … … … … … … … … … … [3] Fig. 1.1 Proceed as follows: 11. Prepare the concentrations of starch solution as stated in (b)(i). 12. Label test-tubes with the concentrations of starch solution you have prepared. 13. Put 3 cm3 of the lowest concentration of starch solution into the labelled test-tube. 14. Repeat step 13 with each of the other concentrations of starch solution. 15. Put 1 cm3 of E into each of the test-tubes. 16. Shake each test-tube gently to mix the contents. 17. Leave the test-tubes for 5 minutes, shaking them occasionally. Relight the Bunsen burner to prepare a boiling water-bath ready for step 19.

6 9700/31/M/J/15 © UCLES 2015 18. After five minutes, put 4 cm3 of Benedict’s into each of the test-tubes. 19. Put the test-tubes containing the two lowest concentrations of starch solution into the boiling water-bath and immediately start timing. 20. Record in (b)(ii) the time taken for the first appearance of any colour change. If there is no colour change after 180 seconds, remove the test-tubes from the water-bath and record ‘more than 180’. 21. Repeat steps 19 and 20 with the remaining test-tubes. (ii) Prepare the space below and record your results, including the result from (a)(ii). [4] (iii) Using your results, calculate the rate at which the product is produced when the concentration of starch is 1%. … s–1 [1] The student’s hypothesis stated that “lowering the concentration of starch below 1% will have no effect on the rate at which the product is produced”. (iv) State whether you support or reject this hypothesis. Explain how your results provide evidence for this decision. support/reject … explanation … … … [2]

7 9700/31/M/J/15 © UCLES 2015 [Turn over (c) (i) Identify one significant source of error in the procedure you carried out between steps 18 and 21. … … [1] The student also stated that “the use of the syringe affected the accuracy of the serial dilutions produced.” (ii) State whether the error when using the syringe is systematic or random and give a reason for your answer. systematic or random … reason … … [1] Fruit juice X contains an inhibitor of enzyme E. Consider how you would modify the procedure you have just carried out to investigate the effect of the concentration of X on the activity of enzyme E. (iii) Describe how the independent variable in the procedure you have just carried out would be standardised in the new investigation. … Describe how the independent variable, concentration of X, will be investigated. … … … … … … … [3] [Total: 22]

8 9700/31/M/J/15 © UCLES 2015 You are required to use a sharp pencil for drawings and graphs. 2 (a) J1 is a slide of a stained transverse section through a plant stem. This plant genus grows widely throughout the world. You are not expected to be familiar with this specimen. (i) Draw a large plan diagram of the quarter of the stem, as shown in Fig. 2.1. draw this quarter Fig. 2.1 Use one ruled label line and the letter T to identify the tissue which is made up of cells that are adapted for the transport of water. [5]

9 9700/31/M/J/15 © UCLES 2015 [Turn over (ii) Select one group of four cells from the tissue (cortex) between the epidermis and the vascular bundle. Each cell in the group should touch two of the other cells. Make a large drawing of this group of four cells. Use one ruled label line and label to identify one cell wall. [4]

10 9700/31/M/J/15 © UCLES 2015 (b) Fig. 2.2 is a stained transverse section through part of the stem of a different plant species. You are not expected to be familiar with this specimen. Y Fig. 2.2 A student calibrated the eyepiece graticule in a light microscope using a stage micrometer scale so that the actual length of the vascular bundle could be found. The calibration was: one eyepiece graticule division equal to 11 μm. Fig. 2.2 shows a photomicrograph taken using the same microscope with the same lenses as the student. Use the calibration of the eyepiece graticule division and Fig. 2.2 to calculate the actual length of the vascular bundle, shown by line Y. You may lose marks if you do not show all the steps in your working and do not use appropriate units. actual length of the vascular bundle … [3]

11 9700/31/M/J/15 © UCLES 2015 (c) The plant in Fig. 2.2 produces fruit that are an important source of food for many animals in the ecosystem in which they grow. A scientist carried out some tests to determine the mass of certain biological molecules found in one of these fruits. The total mass of the fruit was 35 g. The results of the scientist’s investigation are shown in Table 2.1. Table 2.1 biological molecule found in the fruit mass of biological molecule in the 35 g fruit / g carbohydrate (C) 17.0 saturated fat (S) 0.2 unsaturated fat (U) 0.4 fibre (F) 2.4 protein (P) 1.2 (i) Plot a chart of the data shown in Table 2.1. [4] (ii) Calculate the percentage of the fruit that is made up of fat. You may lose marks if you do not show all the steps in your calculation and do not use appropriate units. percentage … [2] [Total: 18]

12 9700/31/M/J/15 © UCLES 2015 BLANK PAGE 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 International Examinations Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cie.org.uk after the live examination series. Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

® IGCSE is the registered trademark of Cambridge International Examinations. CAMBRIDGE INTERNATIONAL EXAMINATIONS Cambridge International Advanced Subsidiary and Advanced Level MARK SCHEME for the May/June 2015 series 9700 BIOLOGY 9700/31 Paper 3 (Advanced Practical Skills 1), maximum raw mark 40 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Report for Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes for the May/June 2015 series for most Cambridge IGCSE®, Cambridge International A and AS Level components and some Cambridge O Level components.

Page 2 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 31 © Cambridge International Examinations 2015 Mark scheme abbreviations: ; separates marking points / alternative answers for the same point R reject A accept (for answers correctly cued by the question, or by extra guidance) AW alternative wording (where responses vary more than usual) underline actual word given must be used by candidate (grammatical variants accepted) max indicates the maximum number of marks that can be given ora or reverse argument mp marking point (with relevant number) ecf error carried forward I ignore

Page 3 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 31 © Cambridge International Examinations 2015 1 (a) (i) (heading) solution(s) or sample + (heading) observation(s) or colour (with iodine) ; (S) blue-black / black + (S and E) any acceptable colour (orange / brown / yellow) ; repeats the experiment ; [3] (ii) records time as a whole number only + seconds / s / sec(s) ; [1] (iii) ref. to hydrolysis / digestion of starch ; [1] (iv) glucose / maltose ; [1] (v) (level of risk) medium or high ; [1] (b) (i) (labels under correct sequence of beakers) 0.5 + 0.25 + 0.125 + 0.0625 + % ; shows transfer of 10 cm3 of solution from previous beaker to 3 beakers ; adds 10 cm3 water / W to 4 beakers ; [3] (ii) 1 (heading) percentage concentration of starch solution ; 2 (heading for any column/row) time + s / second(s) / sec(s) ; 3 records at least 5 results for 5 different concentrations as whole numbers ; 4 records 1% as faster than lowest concentration ; [4] (iii) correct answer calculated from students results ; [1] (iv) reject ; colour change fastest at 1% ; [2] (c) (i) colour change / endpoint is difficult to judge ; [1] (ii) systematic error + same syringe or random error + appropriate problem ; [1] (iii) same concentration of starch ; at least 5 different concentrations of X or fruit juice + serial or simple dilution ; add Benedict’s + heat to 80 °C / boil + record the time for first appearance of any colour change ; [3] [Total : 22]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – May/June 2015 9700 31 © Cambridge International Examinations 2015 2 (a) (i) 1 at least 3 lines + size at least 70 mm + no shading ; 2 no cells + correct quarter drawn ; 3 at least 5 lines drawn + one complete bulge ; 4 at least 3 layers + epidermis drawn as double lines or trichomes drawn ; 5 label T with label line ; [5] (ii) 1 quality of outer line sharp and continuous + largest cell size at least 40 mm in length + at least 4 cells ; 2 only 4 complete cells drawn + each cell must touch another cell at least at one point to form one group ; 3 correct proportion of cell wall to cytoplasm (thin cell walls) ; 4 labels one cell wall ; [4] (b) records correct number of eyepiece graticule units ; shows multiplication by 11 ; correct answer + units ; [3] (c) (i) orientation (x-axis) biological molecule found in fruit + (y-axis) mass (of) biological molecule in the 35 g fruit (/) g ; scale (x-axis) bars of equal width + equal distance apart) + using more than half the grid + (y-axis) even scale ; plotting correct plotting of each bar in the order in the table ; line sharp ruled lines + labels for C, S, U, F, P directly below bar or inside bar ; [4] (ii) shows addition of 0.2 and 0.4 + division by 35 + multiplication by 100 ; 1.7(%) ; [2] [Total: 18]