Cambridge A Level Biology 9700 — 2010 Oct/Nov Paper 3 · Variant 6

This document consists of 9 printed pages and 3 blank pages. DC (CW/SW) 24036/4 © UCLES 2010 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level 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 both questions. 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. * 1 0 7 5 9 1 8 0 7 4 * BIOLOGY 9700/36 Advanced Practical Skills 2 October/November 2010 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions For Examiner’s Use 1 2 Total

© UCLES 2010 9700/36/O/N/10 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 each question and then plan your use of the time to make sure that you finish all of the work that you would like to do. You will gain marks for recording your results according to the instructions. 1 Solution E contains an enzyme which coagulates (clots) milk. You are required to investigate the independent variable, temperature, on the progress of this enzyme-catalysed coagulation. When a mixture of milk and enzyme is gently rotated the coagulation goes through the stages shown in Fig. 1.1. Stage 3 is the end-point of the enzyme-catalysed coagulation. stage 1 stage 2 stage 3 the end-point stage 4 past the end-point film of milk flows/drains back into milk quickly film of milk drains slowly and sticks to inside of test-tube small spots/ clots stick to inside of test-tube as film of milk drains back all the milk has coagulated Fig. 1.1 You are provided with labelled contents hazard volume / cm3 E rennin solution irritant 20 C calcium chloride solution irritant 20 M milk none 100 (a) (i) Decide on the temperatures you plan to use in the range (between) 25 °C to 45 °C. Record the temperatures you have chosen in the space below. … …[2] 2

3 © UCLES 2010 [Turn over 9700/36/O/N/10 For Examiner’s Use Proceed as follows: 1. Label the test-tubes with the temperatures you have chosen. 2. Put 10 cm3 of M into each test-tube. 3. Add 1 cm3 of solution C to each test-tube. 4. Gently shake the test-tube to mix M and solution C. 5. Adjust the temperature of the water-bath you are provided with to your highest chosen temperature. 6. Record the actual temperature of the water-bath. 7. Put the test-tube, labelled with your highest temperature, into the water-bath and leave for three minutes. 8. Remove the test-tube from the water-bath and add 1 cm3 of solution E, so that it runs down the side of the test-tube to form a layer on the surface of the milk as shown in Fig. 1.2. syringe push gently E in syringe slanted test-tube E running down inside of test-tube layer of E forming on top of M and C mixture M and C mixture Fig. 1.2 9. Mix solution E with the milk by gently shaking the test-tube. 10. Start timing and gently rotate the test-tube as shown in Fig. 1.1 to form a film of milk on the inside of the test-tube. Continue to rotate the test-tube and record the time to reach the end-point as shown in stage 3 in Fig. 1.1. Ignore any small bubbles on the inside of the test-tube. 11. Adjust the water-bath to your next highest temperature. 12. Repeat steps 4 to 11.

4 © UCLES 2010 9700/36/O/N/10 For Examiner’s Use (ii) Prepare the space below and record your results. [4] (iii) From your results, state the temperature at which the activity of the enzyme was lowest. …[1]

5 © UCLES 2010 [Turn over 9700/36/O/N/10 For Examiner’s Use (iv) Identify two significant sources of error in this investigation. … … … … … …[2] (v) Describe a suitable control for this investigation. … …[1] (vi) Suggest how you could make this investigation as reliable as possible. … …[1]

6 © UCLES 2010 9700/36/O/N/10 For Examiner’s Use In a similar investigation a student studied the effect of the independent variable pH on the coagulation of milk. The results are shown in Table 1.1. Table 1.1 activity of milk clotting enzyme / arbitrary units pH of milk trial 1 trial 2 trial 3 trial 4 trial 5 mean 6.02 8.8 8.7 8.9 8.2 8.7 6.22 6.8 6.8 6.8 6.7 6.9 6.8 6.40 4.9 4.3 4.4 4.3 4.4 4.4 6.64 1.1 1.0 1.0 0.9 1.0 1.0 6.70 0.7 0.6 1.1 0.5 0.7 0.6 (b) (i) Three of the values in Table 1.1 are anomalous. Draw a circle around each of these values. [1] (ii) Complete Table 1.1 by calculating the missing value. [1] (iii) Plot a graph of the data shown in Table 1.1. [4]

7 © UCLES 2010 [Turn over 9700/36/O/N/10 For Examiner’s Use (iv) Explain the relationship between pH and the enzyme shown in the data. … … … … … …[3] [Total: 20] 2 N1 is a stained transverse section through part of a tubular organ from an animal. (a) (i) Draw a large plan diagram showing the features of the wall of the organ. Label the position of the lumen. [4] (ii) Annotate (make notes with label lines) your diagram to show one difference between the outside layers and the inside layers. [1]

8 © UCLES 2010 9700/36/O/N/10 For Examiner’s Use (b) (i) Fig. 2.1 is a photomicrograph of a stained transverse section through an organ from an animal. The tissue has been stained with special dyes to show the cells and nuclei. cell Y cell X Fig. 2.1 The actual diameter of the nucleus in the cell labelled Y is 7.8 μm. Use this information to calculate the actual mean diameter of the three largest nucleoli in cell Y. You may lose marks if you do not show your working or if you do not use appropriate units. mean diameter of nucleoli in cell Y … μm. [4]

9 © UCLES 2010 9700/36/O/N/10 For Examiner’s Use (ii) Suggest how you would make the measurement of each nucleolus more accurate. … …[1] (iii) Make a large drawing of the cell labelled X with three complete cells touching cell X. [5] (iv) Prepare the space below so that it is suitable for you to compare the cells labelled X and Y. [5] [Total: 20]

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12 9700/36/O/N/10 © UCLES 2010 BLANK PAGE Copyright Acknowledgements: Fig. 2.1 J. W. SHULER/SCIENCE PHOTO LIBRARY 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.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2010 question paper for the guidance of teachers 9700 BIOLOGY 9700/36 Paper 32 (Advanced Practical Skills 2), 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 must be read in conjunction with the question papers and the report on the examination. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2010 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 Question Expected Answers Additional guidance 1 (a) (i) Decide on the temperatures you plan to use in the range (between) 25°C to 45°C. Record the temperatures you have chosen in the space below. [2] [1] at least 5 temperatures; MMO decisions 2 [1] one temp. 25°C to 29°C AND one temp 40°C to 45°C AND any three with two even intervals 3 or more degrees; (ii) Prepare the space below and record your results. [4] Reject • if any units in body of table • only t [1] table with all cells drawn AND heading (top or left) temperature °C; Must have units PDO recording 2 [1] Reject • if units in body of table • if headings for volumes or stages (heading) time with units; [1] temperatures recorded highest to lowest AND first set of times recorded in whole seconds; MMO collection 2 [1] time at the lowest temperature is greater than the next temperature; Allow • only if 3 or more results (iii) From your results, state the temperature at which the activity of the enzyme is lowest. [1] ACE interpretation 1 [1] temperature with longest time AND with units, °C;

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 (iv) Identify two significant sources of error in this investigation. [2] cause of error error [1] (dependent) stage 3 or end-point clots stick small clots coagulation milk drains back slowly idea of seeing determining judging when; [1] (standardised variables) rotation or angle; [1] shaking or mixing or E/enzyme starts to react; [1] E/enzyme temperature; (as milk)/AW AND idea of not constant/different not same timing delayed; ACE interpretation max 2 [1] (independent variable) temperature or test-tube removed from water-bath idea of not constant/not maintained decreasing cools down; Max 2 (v) Describe a suitable control for this investigation. [1] Reject if give two. ACE improvement 1 [1] boil enzyme;

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 (vi) Suggest how you could make this investigation as reliable as possible. [1] C control of any relevant variable [1] equilibrate milk and enzyme to temp. separately then mix Or use thermostatically controlled water bath Or keep tube in water bath during rotation; ACE improvements MAX 1 R1 improve method to get repeat data [1] repeat AND calculate or find mean/average; max 1 (b) (i) Three of the values in Table 1.1 are anomalous. Draw a circle around each of these values. [1] (ii) Complete the Table 1.1 by calculating the missing value. [1] [1] MMO decisions 1 ACE interpretation 1 [1] circles around 8.2, 4.9, 1.1; 8.8 Allow 8.7

Page 5 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 (iii) Plot a graph of the data shown in Table 1.1. [4] O [1] x-axis pH AND y-axis activity (/) arbitrary units or au; Must have units Reject if awkward scale S [1] scale as 0.2 to 2 cm Origin must be labelled as 6 or 6.02 AND 2 to 2 cm; error carried forward if incorrect O then scale x-axis 2 to 2 cm and y-axis 0.2 to 2 cm. must use more than half grid in x and y. Reject plotting if scale is awkward if only dots/blobs or blobs in circles P [1] correct plotting using crosses/dots in circle only; intersection of cross must be clear to show plot. PDO layout 4 L [1] straight line through points; error carried forward if scale or plotting incorrect 6.02 8.8 or 8.7 or ecf 6.22 6.8 6.40 4.4 6.64 1.0 6.70 0.6 quality – not thick, not feathery for the complete line. joining plots – • ruled lines plot to plot • line of best fit • curve through all plots

Page 6 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 (iv) Explain the relationship between pH and the enzyme shown in the data. [3] [1] (in correct context of pH and effect on activity) structure of protein or substrate or enzyme or active site or bonds changed/altered/destroyed/no longer complementary broken; [1] (in correct context of increase in pH and decrease activity) so fewer enzyme-substrate complexes (ESCs) or less/no substrate can bind/combine/attach/fit into OR (in context of decrease in pH and increase in activity) more ESCs or more substrate binds/attaches; ACE conclusions 3 [1] (in correct context of effect of pH on enzyme i.e. when pH higher/nearer 7/less acidic/more alkaline) denatured/denaturation; [Total: 20]

Page 7 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 Question Expected Answers Additional guidance 2 (a) (i) Draw a large plan diagram showing the features of the wall of the organ. Label the position of the lumen. [4] Reject if drawn over print of question PDO layout 1 [1] Reject • thick lines • feathery lines • one ‘tail’ or overlap or gap clear, sharp, unbroken lines AND no shading AND uses most of space provided; Reject if drawn two walls [1] no cells drawn AND three layers drawn include any circles as only one layer; MMO collection 2 [1] Reject if only two layers drawn innermost layer is wider than outermost layer at same point; MMO decisions 1 [1] Reject • if any label is biologically incorrect e.g. regions belonging to other organs or plants. • label within drawn area – e.g. between two walls correct label with label line to or in lumen on inside;

Page 8 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 (ii) Annotate (make notes with label lines) your diagram to show one difference between the outside layers and the inside layers. [1] MMO decision max 1 [1] [1] [1] [1] Reject • if written over lines of the diagram drawing. • if written underneath, unless have labelled on diagram Allow ‘er’ for one label max 1 (b) (i) Actual diameter of the nucleus in the cell labelled Y is 7.8 µm. Use this information to calculate the actual diameter of the largest nucleolus in cell Y. [4] [1] correct measurement of one nucleus, 11 to 15 mm; Reject if no units MMO collection 2 [1] correct measurement of one nucleolus, 2 to 4.5 mm; Reject if no units [1] (mean) adds three measurements AND shows division by 3; PDO display 2 [1] answer to no more than 2 significant figures, (1 decimal place) between 1.1 and 6.4; Reject standard form outermost innermost thickness Reject cell wall thin)ner) think(er); texture smooth rough; cells/nuclei Not clear/densely packed/ visible Clear/less densely packed/(air) spaces/lots Colours/staining of l Pink/red/grey/lighter/more Purple/darker/less;

Page 9 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 (ii) Suggest how you would make the measurement of each nucleolus more accurate. [1] ACE improvement 1 [1] different dimensions/diameters or use vernier callipers or (eyepiece) graticule or increase magnification or high power (of microscope) or enlarging or increase resolution; (iii) Make a large drawing of the cell labelled X with three complete cells touching cell X. [5] Reject if drawn over print of question Reject • thick lines • feathery lines • 2 ’tails’ or overlaps or gaps PDO layout 1 [1] clear, sharp, unbroken lines AND no shading AND uses most of space provided; [1] only cell X and three correct complete touching cells; MMO collection 2 [1] nucleus with at least two distinct nucleoli (other than cell X); [1] chromosomes drawn as two areas (no details of chromosomes shown); MMO decisions 2 [1] blue region/spindle around chromosomes drawn in cell X;

Page 10 Mark Scheme: Teachers’ version Syllabus Paper GCE A LEVEL – October/November 2010 9700 36 © UCLES 2010 (iv) Prepare the space below so that it suitable for you to compare the cells labelled X and Y. [5] [1] organise as a table or Venn diagram or ruled connected boxes headed (cell) X and (cell) Y differences opposite each other; PDO recording 2 [1] heading for similarities/similarity/compare (with contrast)/same; MMO decision 1 [1] has at least one correct similarity, cytoplasm or cell/plasma membrane or shape; Reject tick and cross without a key ACE interpretation max 2 [1] [1] [1] [1] [1] [1] [1] feature (cell) X (cell) Y 1 nucleus/nuclear membrane absent/none/not clear present/clear; 2 nucleoli absent/none/ present/clear; 3 cytoplasm less/not granular more/granular; 4 spindle fibres present/visible absent/none/not visible; 5 chromosomes/chromatid(s) present/visible not visible; 6 cytoskeleton absent/not clear present/clear/visible; 7 cell size small(er) larg(er); Similarities if no organisation then mark points only if in same sentence or following sentences. Allow two ticks for both present i.e. for cytoplasm and shape. Allow differences even if not opposite each other. Allow difference on one side if e.g. use more or –er. max 2 [Total: 20] X Y