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

This document consists of 16 printed pages. DC (SJF/CGW) 57932/6 © UCLES 2013 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level * 7 4 5 9 7 1 1 8 5 2 * BIOLOGY 9700/33 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 9700/33/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 Lipase is an enzyme which catalyses the hydrolysis (breakdown) of triglycerides into fatty acids and glycerol. The substrate for lipase will be the triglycerides present in milk, labelled M. The end-point of this hydrolysis can be determined by using an indicator, P, which changes colour when the fatty acids are produced as shown in Fig. 1.1. Fig. 1.1 You are required to investigate the effect of substrate concentration in M (independent variable) on the lipase-catalysed reaction. You are provided with: labelled contents hazard volume / cm3 M milk none 70 W distilled water none 100 A alkali solution irritant 100 P indicator solution flammable 10 E lipase solution irritant 20

3 9700/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use Proceed as follows: You may assume that the triglyceride content of the milk, M, is 5%. You are required to dilute this 5% milk, M, to provide a range of known concentrations of triglycerides using simple dilution. (a) (i) Decide which three further concentrations of triglycerides to make, then complete Table 1.1. • The difference between each concentration should be 1%. • You will need to make up 20 cm3 of each concentration. Table 1.1 volume of milk solution / cm3 volume of distilled water / cm3 percentage concentration of triglycerides in milk 20 0 5 [2] (ii) State the concentration of triglycerides which you would expect to reach the end-point (pink to white) in the shortest time. …[1] 1. Prepare all the concentrations of triglycerides as in Table 1.1 in the containers provided.

4 9700/33/O/N/13 © UCLES 2013 For Examiner’s Use 2. Put 20 cm3 of A into each of the concentrations which you prepared in step 1 and mix well. 3. Put 3 cm3 of each mixture, as made in Step 2, into separate test-tubes. 4. Put five drops of P into each of the test-tubes and gently shake so that all the mixture turns pink. (Note that each of the concentrations might not be the same shade of pink). 5. Set up a water-bath and adjust the temperature of the water to between 45 °C and 50 °C. You will need to add hot water/cold water to maintain the temperature of the water-bath between 45 °C and 50 °C for steps 6 to 9. 6. Put the test-tubes from Step 4 into the water-bath for five minutes. 7. Put 3 cm3 of M in a test-tube to act as a standard to help you recognise the end-point. Put this test-tube in the water-bath. When you start the timer after adding E to the first test-tube in Step 8, you must not stop the timer at any of the end-points, just record the time. The reaction will start as soon as you add E, so read steps 8 to 13 before proceeding. Continue as follows: 8. Put 2 cm3 of E into the test-tube containing the lowest concentration of triglycerides and mix well, then return it to the water-bath. 9. Start timing and record start time on Fig. 1.2. 10. Immediately, put 2 cm3 of E into the next test-tube containing next highest concentration of triglycerides and mix well, then return it to the water-bath. 11. Record start time on Fig. 1.2. 12. Immediately repeat steps 10 and 11 for the remaining concentrations. 13. Observe the four test-tubes and record the time on Fig. 1.2 when each end-point is reached. This is your raw data. Using the colour of M may help you recognise the end-point. If the time taken to reach the end-point for any one concentration is longer than 5 minutes record ‘more than 300’.

5 9700/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use Step 9 start time … end-point time … start time … end-point time … start time … end-point time … start time … end-point time … Step 11 Step 12 Step 12 Space for you to calculate time to reach end-point Fig. 1.2 From your timer readings you will be required to calculate the time taken to reach the end-point in each test-tube.

6 9700/33/O/N/13 © UCLES 2013 For Examiner’s Use 14. Process your raw data to find the time taken to reach the end-point for each concentration (these are your processed results). If you have time check your results. (iii) Prepare the space below to record your processed results. [5] (iv) Calculate the rate of lipase activity for the 5% concentration of triglycerides. … [1]

7 9700/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (v) Describe how you could set up a control for this investigation using the apparatus provided. … … …[1] (vi) Identify one significant source of error in this investigation. … … …[1]

8 9700/33/O/N/13 © UCLES 2013 For Examiner’s Use Some scientists investigated the effect of the triglycerides in different types of milk (independent variable) on the time taken to reach the end-point. They used the same method as in your investigation. The results are shown in Table 1.2. Table 1.2 type of milk time taken to reach the endpoint / s full fat (F) 130 evaporated (V) 120 low fat (L) 215 condensed (C) 150 dried (D) 265 (b) (i) Plot a chart of the data shown in Table 1.2. [4] (ii) Suggest one reason for the difference in the time taken to reach the end-point between evaporated milk (V) and dried milk (D). … … …[1]

9 9700/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use A student carried out an investigation into the effect of immobilised lipase on the hydrolysis of triglycerides in milk. The student used the apparatus in Fig. 1.3. milk clip used to open and close tube leading from syringe immobilised lipase beads collected milk tested for triglycerides Fig. 1.3 (c) Identify two variables that the student would need to standardise to compare the activity of different concentrations of lipase immobilised in alginate beads. Describe how one of these variables would be standardised. … … … … …[2] [Total: 18]

10 9700/33/O/N/13 © UCLES 2013 For Examiner’s Use 2 K1 is a slide of a transverse section through a plant leaf. This plant grows in the Mediterranean region. (a) (i) Draw a large plan diagram of the part of the leaf 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 an epidermis. [4]

11 9700/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use (ii) Find an area on the specimen in K1 showing a group of four xylem vessels. Choose one group of four whole xylem vessels. Make a drawing of this group, as observed on the specimen on K1. On your drawing, use a label line and label to show one lumen. [5]

12 9700/33/O/N/13 © UCLES 2013 Question 2 continues on page 13

13 9700/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use Fig. 2.2 shows a photomicrograph of a stage micrometer viewed through a microscope. The smallest measurement on this stage micrometer is 0.1 mm. Fig. 2.2 You are required to: • find the area of the field of view, using Fig. 2.2 • count the number of chloroplasts in a quarter of the field of view, using Fig. 2.3 (on page 14) • calculate the number of chloroplasts 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 9700/33/O/N/13 © UCLES 2013 For Examiner’s Use Fig. 2.3 is a photomicrograph showing leaf cells, with the same field of view as in Fig. 2.2. Fig. 2.3 Fig. 2.3 shows chloroplasts in leaf cells. There are too many chloroplasts to count, so the technique of sampling may be used to estimate the number of chloroplasts 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 chloroplasts in the whole field of view. For example, if the number of chloroplasts 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 chloroplasts in the quarter of the field of view. • Mark clearly on Fig. 2.3 each of the chloroplasts counted. • Estimate the total number in the whole field of view. Calculate the number of chloroplasts per mm2. You will lose marks if you do not show your working. number of chloroplasts … mm–2 [4]

15 9700/33/O/N/13 © UCLES 2013 [Turn over For Examiner’s Use Fig. 2.4 is a photomicrograph of a one-celled organism which lives in fresh-water. You are not expected to have studied this organism. The organism has engulfed some green algae (R) which it uses for food. Q x 750 R S Fig. 2.4 (c) (i) Prepare the space below so that it is suitable for you to record the observable differences between Fig. 2.3 and Fig. 2.4. To help you some of the structures on Fig. 2.4 have been labelled with letters. Record your observations in the space you have prepared. [5] Question 2(c)(ii) starts on page 16

16 9700/33/O/N/13 © UCLES 2013 For Examiner’s Use The organism you have observed in Fig. 2.4 is part of a food web. (ii) State the trophic level of the organism in Fig. 2.4. … Describe one observable feature of the specimen in Fig. 2.4 which supports this conclusion. … … …[2] [Total: 22] Copyright Acknowledgements: Fig. 2.4 © MICHAEL ABBEY/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.

CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2013 series 9700 BIOLOGY 9700/33 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 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 33 © 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 33 © Cambridge International Examinations 2013 Expected answers 1 (a) (i) % concentration: 2 + 3 + 4; (volume of milk:) 8 + 12 + 16 with (volume of water) 12 + 8 + 4; [2] (ii) 5%; [1] (iii) organised into table; headings (top or to left of data) percentage concentration of triglycerides + (any column / row headed) time / seconds; records results according to instructions, i.e. for 2, 3, 4, 5%; correct pattern of results between first reading and last; record all results as whole seconds; [5] (iv) correct answer with units, s-1; [1] (v) replace milk / M with water / W or replace enzyme / E with water / W; [1] (vi) one correct error such as difficult to judge end-point or equilibrate contents of all test-tubes; [1] (b) (i) (x-axis) type of milk + (y-axis) time taken to reach end-point (/) seconds; (x-axis) even bar widths up to 2 cm + (y-axis) 100 to 2 cm labelled each 2 cm except label at origin of 0; correct plotting of each bar in order in the table with • horizontal line • ruled • less than 1 mm; bars, quality and labels: • bars must have a space between • all vertical bar lines drawn (including on axis if used), meet horizontal line, ruled lines, • labels must be directly below correct bar or inside bar or shaded with key; [4] (ii) fat concentration higher in evaporated milk (V) than in dried milk (D); [1] (c) two correct variables identified; correct description of how one variable standardized; [2] [Total: 18]

Page 4 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 33 © Cambridge International Examinations 2013 2 (a) (i) drawing and quality (LP of oleander leaf); do not give mark if • any shading • drawn over print of question • any ruled lines • smaller than 60 mm at widest point on mid-rib • less than 4 lines making up upper and lower epidermis or if any part of the line • is too thick • has any feathery or dashed lines or gap in line • has any overlaps; no cells + at least 4 lines and an enclosed area + only part of wall; wavy layer for lower mid-rib or detail of vascular bundle; uses label line and label to epidermis; [4] (ii) drawing and quality; do not give mark if • any shading • drawn over print of question • any ruled lines • smaller than 40 mm across widest point of largest cell • less than 4 enclosed areas or if any outer lines of enclosed areas are • too thick • feathery or dashed or gap in line • have overlaps only four whole cells drawn + at least one cell touching one other vessel; only four whole cells drawn + shape of cells appropriate to xylem vessels; cells walls as double lines for all vessels + three lines where vessels touch; uses label line and labels lumen; [5] (b) (i) 0.2; correct answer (0.126) to no more than 3 significant figures; [2] (ii) marks the chloroplasts that were counted in the quarter shown; multiplies the number of chloroplasts by 4; shows number of chloroplasts divided by area from (b) (i); answer rounded to whole number; [4]

Page 5 Mark Scheme Syllabus Paper GCE AS/A LEVEL – October/November 2013 9700 33 © Cambridge International Examinations 2013 2 (c) (i) mp1 organise as table with three columns or rows separated by lines + two columns headed Fig. 2.3 and Fig. 2.4 in any order + third column or row contains at least one feature; mp feature Fig. 2.3 Fig. 2.4 mp2 Q / cilia absent present; mp3 R / algae absent present; mp4 S / vacuole absent / few present / many; mp5 chloroplasts present absent; mp6 cells multicellular unicellular; mp7 shape rectangular oval / circular; mp8 nucleus absent present; mp9 contents absent present; [max 5] (ii) primary consumer or second trophic level; engulfed green algae; [2] [Total: 22]