Cambridge A Level Biology 9700 — 2014 Oct/Nov Paper 3 · Variant 5

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, graphs or rough working. 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. * 3 0 9 5 8 4 8 8 7 1 * BIOLOGY 9700/35 Advanced Practical Skills 1 October/November 2014 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total This document consists of 15 printed pages and 1 blank page. DC (NH/CGW) 70257/4 © UCLES 2014 [Turn over Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level

2 9700/35/O/N/14 © UCLES 2014 Before you proceed, read carefully through the whole of Question 1 and Question 2. Plan the use of your 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. If you have enough time, consider how you can improve the accuracy of your results, for example by obtaining and recording one or more additional measurements. 1 Enzymes in yeast cells catalyse the hydrolysis (breakdown) of glucose and release carbon dioxide and ethanol. You are required to investigate the effect of different concentrations of yeast cell suspension, Y (independent variable), on the hydrolysis of glucose using methylene blue solution, M, by: • preparing different concentrations of the yeast cell suspension, Y • adding glucose solution, G, to activate the yeast cell suspension, Y, so that M changes colour from blue to blue/green as a result of the activity of the enzymes in the yeast cells. You are provided with: labelled contents hazard volume / cm3 Y 10% yeast cell suspension none 100 G glucose solution none 80 W distilled water none 150 M methylene blue solution stains 20 If any methylene blue solution comes into contact with your skin wash it off immediately with water.

3 9700/35/O/N/14 © UCLES 2014 [Turn over (a) (i) Complete Fig. 1.1 to show how you will dilute Y to prepare a serial dilution. You should use the two beakers shown in Fig. 1.1 and add as many extra beakers as you need to prepare a serial dilution. You will need to prepare 20 cm3 of each suspension. For each beaker, complete Fig. 1.1 to show how you will dilute Y by: • showing under each beaker the concentration and volume of the suspension in this beaker • using one arrow, with a label above the beaker, to show the concentration and volume of yeast cell suspension added • using another arrow, with a label above the beaker, to show the volume of water added. … … … … Fig. 1.1 [3]

4 9700/35/O/N/14 © UCLES 2014 1. Prepare all the concentrations of yeast cell suspension, as shown in Fig. 1.1 on page 3, in the containers provided. You are required to put methylene blue solution with the yeast cell suspension and G. When G is added to the yeast cell suspension the enzymes in the yeast cell suspension will start to catalyse the breakdown of glucose. Methylene blue solution changes colour as these enzymes become active as shown in Fig. 1.2. blue (initial colour ) blue/green no blue or green (colour of yeast/brown) Fig. 1.2 5 minutes after adding G you are required to stop timing and record your observations of the concentrations of yeast cell suspension prepared in (a)(i). Read step 2 to step 9 before proceeding. Proceed as follows: 2. In step 6 you will require a water-bath. Use the beaker or container provided to prepare a water-bath with warm water between 40 °C and 45 °C. You will need to add hot/cold water to maintain the temperature of the water-bath between 40 °C and 45 °C for steps 6 to 8. 3. Put 10 cm3 of the 10% Y into your first test-tube. 4. Put 10 cm3 of each of the other concentrations of yeast cell suspensions that you prepared in step 1 into separate test-tubes. 5. Put 1 cm3 of M into each of the test-tubes. Note that the contents of the test-tubes might be different shades of blue. 6. Put all the test-tubes into the water-bath between 40 °C and 45 °C and leave for two minutes. You will start timing as soon as you add G (in step 7). 7. Leaving the test-tubes in the water-bath put 10 cm3 of G, into each of the test-tubes and gently shake to mix the contents. Start timing. Do not shake the test-tubes again during the investigation. 8. After 5 minutes, stop timing and put the test-tubes in the test-tube rack in the order of the concentrations of yeast cell suspension. 9. Record your observations of each concentration of yeast cell suspension.

5 9700/35/O/N/14 © UCLES 2014 [Turn over (ii) Prepare the space below to record your observations. [5] (iii) You used syringes to measure the volumes of the yeast cell suspension. State the volume of the smallest division on the syringe … State the actual error in using the syringe. actual error … [1] (iv) Identify one significant source of error in measuring the dependent variable in this investigation. … … …[1] (v) Describe one improvement to this investigation which would increase the confidence in your results. … … …[1]

6 9700/35/O/N/14 © UCLES 2014 You are required to use a sharp pencil for graphs. Lactose, a disaccharide sugar, is the main carbohydrate of milk. Some people cannot breakdown lactose and scientists have investigated ways to remove lactose from milk. One type of yeast was found to contain the enzyme, E, that breaks down (hydrolyses) lactose. E can be held within (immobilised) alginate beads and put into milk. As the milk comes into contact with the alginate beads, E hydrolyses the lactose. Scientists have investigated the effect of keeping the alginate beads in contact with the milk for different lengths of time and the percentage hydrolysis of lactose was found. The volumes and concentration of lactose and E were kept the same (standardised). (b) (i) State two other variables that need to be standardised in this investigation. Describe how you would standardise each of these variables. … … … … … … …[3] The results are shown in Table 1.1. Table 1.1 time alginate beads in contact with milk / minutes percentage hydrolysis of lactose 0 0 24 34 52 63 84 81 120 85

7 9700/35/O/N/14 © UCLES 2014 [Turn over (ii) Plot a graph of the data in Table 1.1. [4] (iii) Using your graph state the percentage hydrolysis of lactose at 45 minutes. …% [1] (iv) Explain the reason for the difference in the results at 30 minutes and 70 minutes. … … …[1] (v) Suggest a reason for the change in the trend after 90 minutes. … … …[1] [Total: 21]

8 9700/35/O/N/14 © UCLES 2014 You are required to use a sharp pencil for drawings. 2 Iodine solution and methylene blue solution are used as stains for biological material. You are required to: • observe the effect of using the different stains, iodine solution, I, and methylene blue solution, M, on thin sections of onion tissue, S • observe and record the cells and their cell contents. Iodine solution and methylene blue solution will stain your skin. If any iodine solution or methylene blue solution comes into contact with your skin wash off immediately with water. You are provided with: • three pieces of onion tissue, in a dish labelled S • iodine solution, I • methylene blue solution, M • distilled water, DW. You are required to: • prepare three microscope slides of onion tissue, one using iodine solution, I, one using methylene blue solution, M, and one using distilled water, DW • use the microscope to observe the onion cells after I, M and DW have been added • record your observations by using annotated drawings of two adjacent onion cells from each of the prepared slides. Proceed as follows: 1. Label three dry and clean microscope slides, I, M and DW and put the slides on a paper towel. 2. Put a few drops of: • iodine solution onto slide I • methylene blue solution onto slide M • distilled water onto slide DW.

9 9700/35/O/N/14 © UCLES 2014 [Turn over 3. Remove a piece of the onion tissue from S and, using forceps or fingers peel off the inner concave epidermis as shown in Fig. 2.1. Fig. 2.1 4. Cut three pieces of the epidermis, each smaller than a coverslip. 5. Place one piece of the epidermis onto each of the slides as shown as Fig. 2.2. If the epidermis is folded, you may need to add more drops of I or M or DW so that it floats or uncurls. epidermis iodine solution or methylene blue solution or distilled water slide paper towel Fig. 2.2 6. Cover the epidermis on the slide with a coverslip and use a paper towel to remove any excess liquid that is outside the coverslip. 7. View the slide using the microscope. Look for the thinnest part of the section so that the cells and their contents can be observed. You may need to reduce the amount of light entering the microscope to observe the cells.

10 9700/35/O/N/14 © UCLES 2014 (a) (i) Make a large drawing of two adjacent cells with any observable cell contents from each of: • slide I • slide M • slide DW. Use one ruled label line and label to show one nucleus on one of your drawings. cells from slide I cells from slide M cells from slide DW [6]

11 9700/35/O/N/14 © UCLES 2014 [Turn over (ii) Describe one observable difference between the cells on slide I and the cells on slide M. … …[1] Question 2 continues on page 12

12 9700/35/O/N/14 © UCLES 2014 (b) Fig. 2.3 is a photomicrograph of a stained transverse section through part of an organ from a mammal. You are not expected to have studied this material. taste buds projection magnification × 40 Fig. 2.3 (i) Suggest one observable feature shown by the specimen in Fig. 2.3 which supports the conclusion that this is part of an organ that may absorb molecules. Explain how this feature may help the organ to increase the rate of absorption. feature … explanation … [1]

13 9700/35/O/N/14 © UCLES 2014 [Turn over (ii) Draw a large plan diagram of the projection shown in Fig. 2.3. [4] Question 2 continues on page 14

14 9700/35/O/N/14 © UCLES 2014 Fig. 2.3 is shown again here to help you to answer (c)(i) taste buds E layer width L layer width projection magnification × 40 (c) Fig. 2.4 is a photomicrograph of a stained transverse section through the same organ as Fig. 2.3 but from a different mammal. You are not expected to have studied this material. E layer line E line L L layer projection magnification × 40 Fig. 2.4

15 9700/35/O/N/14 © UCLES 2014 (i) Prepare the space below so that it is suitable for you to show the observable differences between the specimens in Fig. 2.3 and in Fig. 2.4. Record your observations in the space you have prepared. [4] (ii) Calculate the ratio of the width of L (line L) to the width of E (line E) shown within the area indicated on Fig. 2.4. You may lose marks if you do not show your working or if you not use appropriate units. ratio …[3] [Total: 19]

16 9700/35/O/N/14 © UCLES 2014 BLANK PAGE Copyright Acknowledgements: Fig. 2.3 © STEVE GSCHMEISSNER/SCIENCE PHOTO LIBRARY. Fig. 2.4 © WIM VAN EGMOND/VISUALS UNLIMITED, INC./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. 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 October/November 2014 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 2014 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 – October/November 2014 9700 35 © Cambridge International Examinations 2014 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 – October/November 2014 9700 35 © Cambridge International Examinations 2014 1 (a) (i) (10) 5 + 2.5 + 1.25 + 0.625 / 0.63 + percentage at least once ; shows transfer of 20 cm3 of suspension from previous beaker to 4 beakers ; adds 20 cm3 of water / W / H2O to 4 beakers ; [3] (ii) 1 all columns separated by a line + all headings underlined (or all rows separated by a line) ; 2 (top or left of data) percent(age) / % concentration of Y or yeast + (any column / row headed) colour / observation / appearance ; 3 records colours for at least 3 concentrations ; 4 records correct pattern ; 5 repeats ; [5] (iii) ± + half smallest division + cm3 ; [1] (iv) colour (change) + difficult to judge / see / identify ; [1] (v) 1 use different indicator ; 2 repeat ; 3 put glucose solution in water-bath to equilibrate ; 4 use set of colour standards in order to judge final colours ; [max 1] (b) (i) 1 selects two variables ; max 2 for description of 2 methods – must have variable + description: 2 pH + use of buffers ; 3 temperature + use thermostatically-controlled water-bath ; 4 type of milk / age of milk + same type / same age ; 5 size of beads/surface area / number of beads + use ruler / count beads ; [max 3] (ii) 1 (label on x-axis) time alginate beads in contact with milk / minutes / mins + (label on y-axis) percentage / % hydrolysis (of) lactose ; 2 (scale on x-axis) 20 to 2 cm + labelled each 2 cm (except origin and 120) + (scale on y-axis) 20 to 2 cm + labelled each 2 cm (except origin and 100) ; 3 correct plotting of 5 points as small cross or dot (in circle) or cross in a circle ; 4 5 plots + ruled lines exactly point to point or curve through all plots + sharp line (less than line thickness on grid) ; [4]

Page 4 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9700 35 © Cambridge International Examinations 2014 (iii) correct answer according to graph ; [1] (iv) less contact time + fewer enzyme substrate complexes / ESCs ; [1] (v) less substrate available/reference to equilibrium / end product inhibition ; [1] [Total: 21] 2 (a) (i) 1 at least 2 cells in each (I, M and DW) + size at least 60 mm across widest point of widest cell + sharp continuous line for outermost line of each of the cells ; 2 3 groups of 2 cells + in each of the 3 groups the 2 cells touching ; 3 double lines for cell walls (for at least two cells) with middle lamella ; 4 at least one nucleus shown ; 5 nuclei uneven sizes ; 6 label with label line to one nucleus ; [6] (ii) colour different / acceptable answer from candidates drawings ; [1] (b) (i) folds / ridges / pits / grooves / projections / AW + large surface area ; [1] (ii) only three extensions into the projection + width at widest point at least 60mm + no shading ; no cells drawn + only drawn section in the box ; at least one taste bud on each side of projection + irregular upper surface ; draws tissues in correct proportion ; [4]

Page 5 Mark Scheme Syllabus Paper Cambridge International AS/A Level – October/November 2014 9700 35 © Cambridge International Examinations 2014 (c) (i) 1 organise as a table + 2 columns headed Fig 2.3 and Fig. 2.4 (in any order) + third column or row containing at least one feature ; observable differences max 3 – see table below: mp (feature) Fig. 2.3 Fig 2.4 2 furrows between projections / papillae / AW (relative to Fig. 2.4) deep(er) or long(er) wider (relative to Fig. 2.3) shallow(er) or short(er) narrower ; 3 shape of projection / AW (relative to Fig. 2.4) long(er) / columnar / elongated / rectangular / AW not finger-like (relative to Fig. 2.3) Round / oval / circular / shorter / AW ; 4 taste buds (relative to Fig. 2.4) visible / present / large(r) (relative to Fig. 2.3) not seen / absent / small(er) ; 5 E (epithelial layer) surface of layer E (relative to Fig. 2.4) thick(er) / wide(r) / large(r) / long(er) rough / wavy / uneven (relative to Fig. 2.3) narrow(er) / thin(ner) / small(er) / short(er) rounded / smooth ; 6 L layer surface of layer (relative to Fig. 2.4) narrow (er) / thin(ner) / small (er) rounded / smooth (relative to Fig. 2.3) thick(er) / wide(r) / large(r) wavy / uneven / rough ; 7 extensions into projection / AW (relative to Fig. 2.4) 3 extensions / more (relative to Fig. 2.3) 1 extension / less ; [max4] (ii) measures width of line E ± 1 mm + width of line L + units ; shows L divided by E ; answer as larger whole number to: smaller whole number ; [3] [Total: 19]