Cambridge A Level Biology 9700 — 2012 Oct/Nov Paper 3 · Variant 5

This document consists of 12 printed pages. DC (NH/SW) 47061/7 © UCLES 2012 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 0 7 5 6 0 4 1 5 8 5 * BIOLOGY 9700/35 Advanced Practical Skills 1 October/November 2012 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. 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/12 © UCLES 2012 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 • 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 Yeast cells contain an enzyme, catalase, which catalyses the hydrolysis (breakdown) of hydrogen peroxide into oxygen and water with the transfer of heat to the surroundings. The progress of this enzyme-catalysed reaction can be followed by measuring the temperature at intervals of time. You are required to: • make different concentrations of the copper sulfate solution, C • investigate the effect of different concentrations of C (the independent variable). You are provided with: labelled contents hazard volume / cm3 C 3% copper sulfate solution harmful irritant 25 H hydrogen peroxide solution harmful irritant 50 W distilled water none 50 Y yeast suspension low 20

3 9700/35/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use You are required to make a serial dilution of 3% copper sulfate solution, C which reduces the concentration of C by a factor of ten between each successive dilution. You will need to make up 10 cm3 of each concentration of solution C. (a) (i) Complete Fig. 1.1 to show how you will make two further concentrations of C, starting with the 3% solution, C. … … … … … … … … … 1 cm3 of 3% solution C 10 cm3 of 3% solution C Fig. 1.1 [3] Proceed as follows: 1. Make the concentrations of C as stated in (a)(i). 2. Label test-tubes with W and with the concentrations of C. 3. Put 1 cm3 of W into the test-tube labelled W and put 5 cm3 of H into the same test-tube. Mix well. 4. Put a thermometer into the contents of the test-tube. Record the temperature. 5. Stir Y and put 1 cm3 of Y into the same test-tube. Mix well. 6. Start timing and record the temperature of the contents of the test-tube every 30 seconds up to 210 seconds.

4 9700/35/O/N/12 © UCLES 2012 For Examiner’s Use 7. Repeat steps 3 to 6 replacing the 1 cm3 of W with 1 cm3 of the lowest concentration of C. 8. Repeat step 7 with the other concentrations of C. (ii) Prepare the space below to record your results. [5] (iii) Explain the effect of the 3% copper sulfate solution on the enzyme-catalysed reaction. … … …[1] (iv) Identify two significant sources of error in this investigation. … … … … …[2]

5 9700/35/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use (v) Describe three modifications to this investigation which would improve the confidence in your results. … … … … … … … …[3] (vi) Describe how you would set up a control for this investigation. … …[1] (vii) State the value of the smallest division on the scale of your thermometer. smallest division … State the actual error in measuring a temperature of 30 °C using this thermometer. 30 °C ± … °C [1]

6 9700/35/O/N/12 © UCLES 2012 For Examiner’s Use In a similar investigation, a student investigated how changing the concentration of catalase solution (independent variable) affected the hydrolysis of hydrogen peroxide. The student stopped the reaction after one minute by adding a high concentration of sodium azide. A dye was added which reacted with the hydrogen peroxide that had not been hydrolysed. This produced different intensities of colour depending on the quantity of the remaining hydrogen peroxide in the solution. A colorimeter was used to measure the absorbance of light by the coloured solution. Other variables were considered and kept to a standard. The results of the student’s investigation are shown in Table 1.1. Table 1.1 concentration of catalase solution / arbitrary units absorbance of light by the coloured solution / arbitrary units 10 1.34 14 1.12 30 0.66 50 0.04 100 0.02

7 9700/35/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use (b) (i) Plot a graph of the data shown in Table 1.1. [4] (ii) Explain the relationship between the concentration of catalase solution and the hydrolysis of hydrogen peroxide. … … … … …[2] [Total: 22]

8 9700/35/O/N/12 © UCLES 2012 For Examiner’s Use 2 L1 is a slide of a transverse section showing a tubular part of the digestive system of a mammal. You are not expected to have studied this material. (a) Draw a large plan diagram showing only the features of the wall of the tube as in the sector shaded in Fig. 2.1. Fig. 2.1 On your diagram, use a label line and label to show the position of the lumen. Annotate your diagram to describe one difference between the innermost layer and outermost layer. [5]

9 9700/35/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use Fig. 2.2 shows a diagram of a view of a stage micrometer scale that is being used to calibrate an eyepiece graticule. One division, on either the stage micrometer scale or the eyepiece graticule, is the distance between two adjacent lines. The length of one division on this stage micrometer is 0.1 mm. Fig. 2.2 (b) (i) Using this stage micrometer, where one division is 0.1 mm, calculate the actual length of one eyepiece graticule unit using Fig. 2.2 by completing Fig. 2.3. Step 1 1 eyepiece graticule unit = divided by = … mm Step 2 Convert the answer to a measurement with the unit most suitable for use in light microscopy. multiplied by = … Fig. 2.3 [3]

10 9700/35/O/N/12 © UCLES 2012 For Examiner’s Use Fig. 2.4 is a photomicrograph showing a transverse section through a part of the specimen on slide L1. X Z Fig. 2.4 (ii) Fig. 2.4 shows a photomicrograph taken using the same microscope with the same lenses as Fig. 2.2. Use the calibration of the eyepiece graticule unit from (b)(i) and Fig. 2.4 to calculate the actual length of the fold shown by X to Z. You will lose marks if you do not show all the steps in your calculation and do not use the appropriate units. [2]

11 9700/35/O/N/12 © UCLES 2012 [Turn over For Examiner’s Use Fig. 2.5 is a photomicrograph showing a transverse section through a part of the specimen on slide L1. P Fig. 2.5 (c) Make a large drawing of the four cells, labelled P, on Fig. 2.5. On your drawing, use a label line and label to show one nucleus. [4] Question 2 continues on page 12

12 9700/35/O/N/12 © UCLES 2012 For Examiner’s Use Fig. 2.6 is a photomicrograph showing a transverse section through a different organ in the same mammal. ×40 Fig. 2.6 (d) Prepare the space below so that it is suitable for you to record two observable differences between the specimen on slide L1 and in Fig. 2.6. [4] [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. 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 2012 series 9700 BIOLOGY 9700/35 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 October/November 2012 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 2012 9700 35 © Cambridge International Examinations 2012 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 ACE Analysis, Conclusions and Evaluation (skills) MMO Manipulations, Measurement and Observation (skills) PDO Presentation of Data and Observations (skills)

Page 3 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 1 (a) (i) [3] mp 1 (labels for concentration under correct sequence of beakers) (0).3 AND (0).03; (for dilution of C) cm3 or ml(s) shown AND shows transfer of 1 (cm3) of 0.3 (%) to next dilution or shown by arrow; mp 2 Do not give mark if incorrect concentrations MMO decision 3 mp 3 (for water) adds 9 cm3 of (distilled) water /W to each of the two beakers AND must add previous concentration to third beaker; (ii) [5] table with all cells drawn AND heading (top row or column to left of recorded data) percent(age) or % conc(entration) of C or copper sulfate or [ C ] OR only time (with) s or sec(onds); mp 1 Can have Ignore Do not give mark if • no outer boundary • test-tube /additional columns • notes outside area • t or T • % in cells of headed column • other units e.g. mol dm–3 • no percentage or % • units in cells of this column/row e.g. 45’ (units) • min(utes) • more than one row in one cell for multiple trials (heading for any column/row including mean) temp(erature) (/) °C; PDO recording 2 mp 2 Ignore Do not give mark if • if have columns/rows for test-tubes or observations e.g. effervescence • any notes outside area • heading for test-tubes/heading for time • t or T • headings for volumes or method information or in cells e.g. volumes and concentrations in same cell

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 mp 3 (mark first column / row) records at least four results as whole numbers or to half a degree only for 30 seconds that is any whole number or 0.5 °C, which is less than 35 and more than 15; (mark first column / row of recorded temperature for recording correct pattern) for W/ water / 0, temperature at 210 seconds higher than temperature at 30 seconds; mp 4 Must have units for temperature recorded somewhere, e.g. °C MMO collection 3 mp 5 in column / row for concentration/solution the order is W and then from their lowest concentrations to 3%; (water to left for row or top if column) (iii) [1] Must have results for water, 0.03% and 3% AND results for lowest temperature recorded e.g. initial temperature / 30 seconds AND results for 210 seconds; (if change in temperature from 0 to 210 seconds for 3% is LESS compared to water/0.03%) inhibition/ (reaction) slows down/less active/fewer ESCs/describes blocking active sites/denatured (if change in temperature from 0 to 210 seconds for 3% is MORE compared to water/0.03%) more active/reaction speeds up/more active/ more ESCs/ cofactor ACE conclusion 1 (if change in temperature from 0 to 210 seconds for 3% is SAME compared to water/0.03%) (allow 0.5°C difference) no effect

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 (iv) [max 2] cause of error WITH idea of error mp 1 starting / initial temperature not same / different / changes; mp 2 thermometer position not same / different / changes; mp 3 mixing (of W, H and Y and/or C, H and Y) not same for each test-tube / different / changes; ACE interpretation max 2 mp 4 concentration of hydrogen peroxide / substrate changes / decreases; (v) [max 3] mp 1 use thermostatically (controlled) water bath; Do not give if temperature controlled room / air conditioning mp 2 (dependent variable) use data logger with temperature sensor / digital thermometer / thermometer with narrower calibration; mp 3 use magnetic stirrer / mechanical stirrer (to standardise stirring); mp 4 (standardised variables) cover or use ‘fresh’ / from bottle hydrogen peroxide; mp 5 (independent variable) more / wider / narrower range of concentrations (of C); mp 6 (dependent variable) record for longer OR for longer intervals OR repeats / replicate experiment / multiple tests; ACE improvements max 3 mp 7 insulate test-tubes / describes method; (vi) [1] Idea of • replace C / copper sulfate with water • W/water and Y / yeast suspension and H / hydrogen peroxide • replace Y / yeast suspension with water/beads; MMO decision 1 Do not give • just remove C / copper sulfate • boil enzyme / Y

Page 6 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 (vii) [1] half of smallest division (whatever stated as smallest division); ACE interpretation 1 Do not give for any figure less than (0).25 (b) (i) [4] O x-axis conc(entration) of catalase (/) arbitrary units / (au) AND y-axis absorbance of light (by the coloured solution) (/) arbitrary units (au); S scale as x-axis 20 to 2 cm labelled each 2 cm except origin and 100 need not be labelled AND y-axis 0.2(0) to 2 cm labelled each 2 cm except origin and 1.4(0) need not be labelled; P correct plotting of • five points • as small cross (use square on grid) or dot (in circle, use grid) or cross in circle to within half a square; PDO layout 4 L Five plots joined with ruled lines exactly point to point AND (quality) smooth line less than 1 mm thick (use grid); Additional guidance: O S Must have label of value of origin if zero not at origin ecf if no labels for O but numbers show orientation is correct then must have scale as normal. If reverse orientation then only x-axis 0.4 to 2 cm y-axis 20 to 2 cm P Can have Do not give if • ecf if x- and y-axis reversed if x-axis 0.4 to 2 cm y-axis 20 to 2 cm • any blobs or dots • any cross too large with any part of cross outside square on grid or dot larger than circle on grid

Page 7 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 L Can have Do not give if • ecf from incorrect P • any feathery or gap in line • any irregular thickness • any extrapolation either end (ii) [2] mp 1 more enzyme-substrate-complexes / ESCs / more active sites binding to hydrogen peroxide / substrate; ACE conclusions 2 mp 2 less hydrogen peroxide / substrate available / all gone / none left / hydrogen peroxide limiting factor; [Total: 22] 2 (a) [max 5] quality of plan diagram; Do not give if • drawn over the print of question or any shading or wiggly lines anywhere or any ruled or compass lines • complete section • drawn both walls • thickness of wall smaller than 60 mm across widest point AND (clear, sharp, unbroken lines) ; • less than 5 hand drawn lines PDO layout 1 mp 1 the outermost line and innermost line • any part of the line 1mm or thicker • any feathery or dashed or gap in line • any ’tails’ or overlaps mp 2 no cells drawn AND only sector of wall drawn; Do not give if • two walls (not sector drawn) • complete sector MMO collection 2 mp 3 drawn 5 layers (6 lines);

Page 8 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 labels lumen with label line into the space below innermost line; mp 4 Ignore Do not give if • any labels identifying tissues associated with animal • label is written between the innermost and outermost lines • any label which is biologically incorrect e.g. plant • any label written between the innermost and outermost lines MMO decision 2 mp 5 correct annotation with at least one label line; inner wall outer wall folded rough irregular not folded smooth regular tightly packed cells loosely packed cells many nuclei fewer nuclei/no nuclei no cells cells present difference in density/colour of staining (b) (i) [3] MMO decision 1 mp 1 (Step 1) answer ( = .. mm) must be 0.004 (0) OR expressed in standard form 4 x 10–3; (either box in step 2) 1000 OR 103 AND answer from step 1 in other box; PDO display 1 mp 2 ecf any answer to step 1 µm AND answer from step 1 x 1000; ACE interpretation 1 mp 3 freestanding mark in isolation from answers to boxes in step 2

Page 9 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 (ii) [2] measures correctly in eyepiece graticule units 51 to 65 (epg units); MMO collection 1 mp 1 Do not give if • µm or mm or cm or m shows multiplication by answer from (b) (i) any one value (multiplied by) x by answer from (b) (i) step 2; PDO display 1 mp 2 Can have • alternative signs . or * Do not give if • if any division shown (c) [4] PDO layout 1 mp 1 quality of drawing; Do not give if • drawn over the print of question or any shading anywhere orany ruled or compass lines smaller than 50 mm across widest cell less than 4 cell outlines • any of outermost lines have • any line 1 mm or thicker (use grid) • any feathery or dashed line or gap in line • any ’tails’ or overlaps only four complete cells drawn AND cell 1 must touch cells 2 and 3; mp 2 Do not give if • any ruled or compass lines at least two nuclei with both drawn either in contact with a single line (either side of a line) or within two lines; MMO collection 2 mp 3 Do not give if • drawn EM organelles e.g. mitochondria • all cells drawn separately labels only one nucleus with ruled label line touching either outer line of enclosed area or ending inside enclosed area; MMO decision 1 mp 4 Do not give if • any label other than nucleus, ignore label lines and P • any label within drawn area

Page 10 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2012 9700 35 © Cambridge International Examinations 2012 (d) [4] organise as a table with only three columns or rows separated by lines (no cells needed) Ignore number column AND headings in any order only L1 / slide and Fig. 2.6 AND third column/row contains list of features; mp 1 (features) L1 Fig. 2.6 (L1 or Fig. 2.6 either way round and other column to left, right or in middle only differences (all recorded); PDO recording 2 mp 2 Do not give if • any similarities recorded • any functions • any EM features ACE interpretation max 2 max 2 Do not give if any ref. to membranes/vacuoles/tunica feature L1/slide Fig. 2.6 1 (number of folds / folding) (inner layer / surface) highly folded / more / many less folded / less/few(er); 2 (size of folds / innermost layer) (shape of folds / lumen) large(r) / thick(er) rough / less smooth / irregular/ wavy small(er)/ thin(ner) more smooth / regular/rectangular 3 contents of lumen has/present none 4 cartilage (‘middle tissue’) no (one) / absent/has not continuous yes / present/has discontinuous / has break; 5 number of layers either way; 6 nuclei more less [Total 18]