Cambridge A Level Biology 9700 — 2013 Oct/Nov Paper 3 · Variant 5

This document consists of 15 printed pages and 1 blank page. DC (LEO/CGW) 86884/7 R © UCLES 2013 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 6 4 5 7 0 8 4 4 2 6 * BIOLOGY 9700/35 Advanced Practical Skills 1 October/November 2013 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 ink. You may use a pencil for any diagrams, graphs or rough working. Do not use red ink, staples, paper clips, highlighters, 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 9700/35/O/N/13 © UCLES 2013 For Examiner’s Use You are reminded that you have only one hour for each question in the practical examination. You should: • read carefully through the whole of Question 1 and Question 2 • then plan your use of the time to make sure that you finish all the work that you would like to do. You will gain marks for recording your results according to the instructions. 1 Plant cells contain enzymes which catalyse some of their metabolic reactions. Some of these enzymes catalyse the release of oxygen from hydrogen peroxide solution. A plant extract solution can be produced which will contain these enzymes. You are required to investigate the effect of hydrogen peroxide (independent variable) when mixed with a plant extract solution. You are provided with: labelled contents hazard volume / cm3 P plant extract solution none 15 H 6% hydrogen peroxide solution irritant harmful 50 W distilled water none 100 D liquid detergent none 15 Proceed as follows: You are required to change the concentration of the hydrogen peroxide solution (the independent variable).

3 9700/35/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (a) (i) Decide which concentrations of hydrogen peroxide to make: • using serial dilution, • using 40 cm3 6% hydrogen peroxide solution, H, to start the serial dilution, • reducing the concentration by half between each concentration. Complete Fig. 1.1 to show how you will make three further concentrations. … … … … 40 cm3 of 6 % H … … … … … … … … Fig. 1.1 [3]

4 9700/35/O/N/13 © UCLES 2013 For Examiner’s Use 1. Prepare all the concentrations of hydrogen peroxide, as in Fig. 1.1, in the containers provided. When detergent is mixed with H and then P (containing the enzyme), oxygen is released and the bubbles form a foam on top of the mixture. You are required to measure the release of oxygen by measuring the total height of the mixture and the foam and the height to where the mixture meets the foam, as shown in Fig. 1.2. You are provided with a graph paper scale on a piece of card. Fig. 1.2 shows how to use the graph paper scale to measure the total height of the mixture and foam and the height to where the mixture meets the foam. 2. Fold the graph paper scale along one of the thicker lines and label this line 0 as shown in Fig. 1.2. You may find it useful to label each 10 mm as shown on Fig. 1.2. foam total height of the mixture and foam height to where the mixture meets the foam graph paper scale fingers supporting the bottom of the test-tube and the folded graph paper Fig. 1.2

5 9700/35/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use 3. Put 5 cm3 of the 6% concentration of H into a test-tube. 4. Put 4 or 5 drops of D into the same test-tube. So that D does not come into contact with the wall of the test-tube, you should release the drops close to the top of H. 5. As shown in Fig. 1.3, stir H and D until mixed together. The reaction will start as soon as you put P into the mixture of H and D. Read steps 6 to 9, before proceeding. stirrer H and D syringe push gently P Fig. 1.3 Fig. 1.4 6. As shown in Fig. 1.4, put 1 cm3 of P into the same test-tube and stir as before. Immediately start timing. 7. Hold the test-tube as shown in Fig. 1.2. Every 60 seconds until 180 seconds, record the: • total height of the mixture and foam • height of the mixture where it meets the foam. If the foam reaches the top of the test-tube before 180 seconds: • stop timing • record ‘total height to the top of test-tube’ • record the height of the mixture where it meets the foam.

6 9700/35/O/N/13 © UCLES 2013 For Examiner’s Use To process your results you may find it helpful to record your raw measurements on Fig. 1.5. 60 seconds 120 seconds 180 seconds … … Fig. 1.5 8. Repeat steps 3 to 7 with each of the remaining concentrations. 9. Process your raw results to find the height of the foam. If you have time, check your results. You may use the space below to record your raw measurements.

7 9700/35/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (ii) Prepare the space below to record, for each concentration, the processed results only for the maximum height of foam. [5] (iii) Identify two significant sources of error in this investigation. … … … … …[2]

8 9700/35/O/N/13 © UCLES 2013 For Examiner’s Use (iv) Describe how you would modify this procedure to investigate the effect of copper sulfate concentrations on the enzyme in the plant extract solution. … … … … … … …[3] (b) Some scientists investigated the effect of copper sulfate solution on the release of oxygen from hydrogen peroxide solution, in the presence of a plant extract. All the variables were standardised. They set up two test-tubes: • one with 1 cm3 of distilled water, hydrogen peroxide and plant extract • one with 1 cm3 of copper sulfate solution, hydrogen peroxide and plant extract. The number of bubbles of oxygen released in each 60 seconds for 300 seconds were recorded. The results are shown in Table 1.1. Table 1.1 time / s number of bubbles of oxygen released with 1 cm3 of distilled water with 1 cm3 of copper sulfate solution 60 99 69 120 96 4 180 65 0 240 34 0 300 4 0

9 9700/35/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (i) Plot a graph of the data in Table 1.1. [4] (ii) Explain the effect of the copper sulfate solution on the enzymes in the plant extract. … … … … … … …[3] [Total: 20]

10 9700/35/O/N/13 © UCLES 2013 Question 2 starts on page 11

11 9700/35/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use 2 L1 is a slide of a transverse section through a plant leaf. This plant species grows widely including tropical, sub-tropical and temperate regions. (a) (i) Draw a large plan diagram of the part of the leaf on L1 indicated by the shaded sector in Fig. 2.1. draw this sector Fig. 2.1 On your diagram, use a ruled label line and label to show the vascular bundle. [5]

12 9700/35/O/N/13 © UCLES 2013 For Examiner’s Use (ii) Make a drawing of one group of adjacent (touching) cells, as observed on the specimen on L1, made up of: • three epidermal cells • three of the palisade cells touching these epidermal cells. On your drawing use a label line and label to show one palisade cell. [5]

13 9700/35/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use Fig. 2.2 shows a stage micrometer viewed through a microscope with an eyepiece graticule scale. The smallest measurement on this stage micrometer is 0.1 mm. 0 100 white circle Fig. 2.2 You are required to: • find the area of the field of view, using Fig. 2.2 • count the number of stomata in a quarter of the field of view, using Fig. 2.3 (on page 14) • calculate the number of stomata per mm2. (b) (i) Calculate the area of the field of view, using: • the formula for the area of a circle πr2 • π = 3.14 • r = radius of the field of view. You will lose marks if you do not show your working or if you do not use appropriate units. area of field of view … mm2 [2]

14 9700/35/O/N/13 © UCLES 2013 For Examiner’s Use Fig. 2.3 is a photomicrograph of the lower surface of a leaf, with the same field of view as in Fig. 2.2. Fig. 2.3 Fig. 2.3 shows stomata on a leaf surface. There are too many stomata to count so the technique of sampling may be used to estimate the number of stomata in the field of view. A sample should be counted in a known smaller portion and then the result multiplied to obtain an estimate of the number of stomata in the whole field of view. For example, if the number of stomata is counted in a quarter of the field of view then this number would be multiplied by 4 to obtain the estimate of the total number in the field of view. (ii) Count and record the sample number of stomata in the quarter of the field of view shown in Fig. 2.3. • Mark clearly on Fig. 2.3 each of the stomata counted. • Estimate the total number in the whole field of view. Calculate the number of stomata per mm2. You will lose marks if you do not show your working. number of stomata … mm–2 [4]

15 9700/35/O/N/13 © UCLES 2013 For Examiner’s Use Fig. 2.4 is a photomicrograph of the lower surface of a different leaf, with the same field of view (using the same lenses) as Fig. 2.3. Fig. 2.4 (c) Prepare the space below so that it is suitable for you to record the observable differences between the surface of each leaf shown in Fig. 2.3 and Fig. 2.4. Record your observations in the space you have prepared. [4] [Total: 20]

16 9700/35/O/N/13 © UCLES 2013 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. University of 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.

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2013 series 9700 BIOLOGY 9700/35 (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 October/November 2013 series for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level components and some Ordinary Level components.

Page 2 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 35 © Cambridge International Examinations 2013 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 excepted) 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 GCE AS/A LEVEL – October/November 2013 9700 35 © Cambridge International Examinations 2013 1 (a) (i) (labels under correct sequence of beakers) correct halving 3 + 1.5 + 0.75 with % once; transfers 20 from second beaker to third, third to fourth etc. + cm3; adds 20 (distilled) water to each beaker + cm3; [3] (ii) organised into a table; heading (column to left of data or top row) percentage or % concentration of hydrogen peroxide or H + (any column / row headed) height or length of foam + mm; records results according to instructions i.e. 4 concentrations with highest concentration first and lowest concentration is last; correct pattern of results, records a value for 6% which is higher than any one of the other results; only recorded the processed maximum height + values to whole mm or 0.1 cm; [5] (iii) cause of error + idea of error: bubbles / foam at top + not same or difficult to judge or varies or different; tube + changes as held or not vertical or not the same; holding / hand + may warm up tube or temperature changes; test-tubes + different or vary or not same; stirring + different or vary or not the same; drops of detergent + different sizes / volumes / detergent sticks to the sides; timing + different or vary or not the same / reaction started before timing; [max 2] (iv) (independent variable) at least five differerent concentrations of copper sulfate or gives five examples; (how made) serial dilution or simple dilution or method must match any examples of concentrations given in mp1, do not give mark if stated concentrations cannot be made by the stated dilution method (e.g. serial dilution cannot make 20%, 30%, 40%, 50%, 60%) any of the following: same volume / concentration of hydrogen peroxide or example given or same volume of copper sulfate or example of a volume given or same volume / concentration of plant extract or example given; [3] (b) (i) line graph: label on x-axis time (/) s or sec(onds) + label on y-axis number of bubbles of oxygen released; scale x-axis 50 to 2 cm labelled each 2 cm + y-axis 20 to 2 cm labelled each 2 cm; correct plotting of five of the plotted points as small cross or dot in circle; ruled lines through five plotted points for distilled water; ruled lines must not be too thick [4]

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 35 © Cambridge International Examinations 2013 (ii) (idea of) binds or fits enzyme or active site or alters or changes the shape of the enzyme or active site or denatures enzyme; H or substrate no longer fits active site or fewer or no Enzyme-Substrate Complexes / ESCs are formed or described; inhibition or inhibitor; [3] [Total: 20] 2 (a) (i) drawing and quality; do not give mark for • any shading • any ruled lines • smaller than 60 mm across widest dimension of largest enclosed area • less than 2 lines for the upper epidermis and 2 lines for the lower epidermis or if any line • is too thick • has feathery or dashed lines or gap in line • has any overlaps; no cells + at least 4 lines and one enclosed area + midrib with lamina each side; convex top and bottom line across midrib; third line under the upper epidermis (for palisade layer); uses label line with label to vascular bundle; [5] (ii) drawing and quality; do not give mark for • any shading • any ruled lines • smaller than 40 mm across widest dimension of largest cell • less than 6 cells / enclosed areas or if any line • is too thick • has any feathery or dashed lines or gap in line • has any overlaps draws only three palisade cells and three epidermal cells + as one group (all cells touch at least one other cell); no more than one rectangular (palisade cell) + palisade cells should all touch an (epidermal) cell; all cells must be drawn with double lines + three lines where cells touch; uses label line with label to only one palisade cell. [5]

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 35 © Cambridge International Examinations 2013 (b) (i) 1 0.8; 2 2 or 2.0 or 2.01; [2] (ii) marks on stomata that were counted in quarter; show a whole number multiplied by 4 (only); shows any whole number divided by answer from 2 (b) (i); rounded to whole number for answer; [4] (c) mp1 organise as table with three columns separated by lines or three rows separated by lines no cell lines needed + two columns headed Fig 2.3 and Fig 2.4 in any order + third column or row contains at least one feature; Any two of: [max 4] [Total: 20] mp feature Fig. 2.3 Fig. 2.4 mp2 number of stomata more or example of a number closer packed / nearer /gap narrower / clustered few(er) or example of a number; mp 3 size of stomata or epidermal cells or guard cells small(er) large(r); mp 4 shape of stomata oval or slit or elongated round(er) or circular; mp 5 guard cell shape stomata or guard cells oval or elongated (more) closed or fewer open round(er) or circlular; (less) open or more open; mp 6 epidermal cell shape or pattern of lines very irregular or not clear folded clear or angular or corners smoother; mp 7 epidermal cell walls thin(ner) thick(er);