Cambridge A Level Biology 9700 — 2005 May/June Paper 5 · Variant 1

This document consists of 7 printed pages and 1 blank page. SP (MML 8289 4/04) S81909/2 © UCLES 2005 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level BIOLOGY 9700/05 Paper 5 Practical Test A2 May/June 2005 1 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in Instructions to Supervisors Centre Number Candidate Number Name READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work that you hand in. Write in dark blue or black pen in the spaces provided on the Question Paper. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. Answer both questions. The number of marks is given in brackets [ ] at the end of each question or part question. You are advised to spend 45 minutes on question 1. If you have been given a label, look at the details. If any details are incorrect or missing, please fill in your correct details in the space given at the top of this page. Stick your personal label here, if provided. For Examiner’s Use 1 2 Total

1 You are required to investigate the light-dependent stage in photosynthesis in a leaf extract, using the dye DCPIP. When DCPIP is reduced, it changes from a blue colour, to colourless. You are required to produce a leaf extract from material provided. Procedure to make a leaf extract ● Place the piece of fresh leaf, C1, on a white tile. ● With a scalpel, carefully remove any large veins and discard them. ● Chop the rest of the leaf into small pieces. ● Place the chopped leaf into a plastic specimen tube. ● Using a syringe or pipette, add 2 cm3 of cold buffer solution, labelled C2, to the specimen tube. ● Add a spatula full of sand, labelled C3. Carefully grind the chopped leaf in the specimen tube, using a glass rod for about one minute to obtain a green leaf extract. ● Clean the surface of the white tile with a paper towel. ● Place a Petri dish on the edge of the tile as shown in Fig. 1.1, so that the dish is tilted. ● Pour the leaf extract from the specimen tube into the Petri dish and allow it to drain to the edge of the dish as shown in Fig. 1.1. Fig. 1.1 ● Completely cover the Petri dish with aluminium foil to shield the contents from light. The foil should be made easy to remove. Leave the foil in position except when removing samples. ● Take a capillary tube and stand one end of the tube in the leaf extract. Some of the extract will immediately rise a short distance up the tube. Remove the tube and lay it on the tile as a colour standard. Label this Tube 1. ● You are provided with a 1% solution of DCPIP, labelled C4. Using a teat pipette, add five drops of C4 solution to the leaf extract. Tilt the dish to mix the two liquids (or mix with the teat pipette). Ensure that the foil cover is replaced. white tile leaf extract petri dish base or lid 2 9700/05/M/J/05 For Examiner’s Use © UCLES 2005

● Take a second capillary tube and collect some leaf extract / C4 mixture. Immediately replace the foil cover and wrap the tube quickly in aluminium foil to prevent any exposure to light. Lay the tube on the tile. Label this Tube 2. ● Take a third capillary tube and collect some leaf extract / C4 mixture. Place the tube near a bench lamp. Label this Tube 3. ● Carefully check the colour of the liquid in all of the tubes, every minute, ensuring that the foil on Tube 2, is replaced each time. ● Note the time taken for the dye in Tubes 2 and 3 to be reduced. ● If there is no change in colour after 10 minutes, stop the investigation. (a) Draw a table to show your results. [4] (b) Explain your results in relation to the light-dependent stage of photosynthesis. … … … … … [3] (c) Suggest why C2 and C4 were kept in a beaker of ice so that the solutions were cold when they were being used. … … … [3] 3 9700/05/M/J/05 [Turn over For Examiner’s Use © UCLES 2005

(d) Explain the purpose of using the buffer solution, C2. … … [1] (e) The buffer solution also contained some sucrose. Suggest why sucrose was added to the buffer solution. … … [1] (f) Suggest how the investigation could be improved to make the results more reliable. … … … … … [3] [Total : 15] 4 9700/05/M/J/05 For Examiner’s Use © UCLES 2005

2 Fig. 2.1 is a photomicrograph of human blood. Fig. 2.1 (a) Determine the ratio of red blood cells to white blood cells. ratio … [2] (b) You are provided with a slide of human blood, labelled K1. Choose an appropriate magnification so that you can clearly see both red and white blood cells in your field of view. The white blood cells have been stained blue for easy identification. (i) Explain why it would be difficult to determine the exact ratio of red blood cells to white cells in slide K1. … … … [2] (ii) Comment on the ratio of red blood cells to white blood cells when compared with the ratio you determined in (a). … [1] 5 9700/05/M/J/05 [Turn over For Examiner’s Use © UCLES 2005

(c) Fig. 2.2 is the same photomicrograph of blood, as is shown in Fig. 2.1. Fig. 2.2 In the spaces below, draw to the same scale, labelled diagrams of: (i) a red blood cell. 6 9700/05/M/J/05 For Examiner’s Use © UCLES 2005

(ii) a phagocyte. (iii) a lymphocyte. [8] (iv) Draw a line, on Fig. 2.2, across the lymphocyte. The actual diameter of a red blood cell is 8
m. Use this information to calculate the width of the lymphocyte along the line drawn. width of lymphocyte … [2] [Total : 15] 7 9700/05/M/J/05 For Examiner’s Use © UCLES 2005

8 9700/05/M/J/05 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 University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Level MARK SCHEME for the June 2005 question paper 9700 BIOLOGY 9700/05 Paper 5 (Practical Test A2), maximum raw mark 30 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. This shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the Report on the Examination. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the June 2005 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Grade thresholds for Syllabus 9700 (Biology) in the June 2005 examination. minimum mark required for grade: maximum mark available A B E Component 5 30 24 22 16 The thresholds (minimum marks) for Grades C and D are normally set by dividing the mark range between the B and the E thresholds into three. For example, if the difference between the B and the E threshold is 24 marks, the C threshold is set 8 marks below the B threshold and the D threshold is set another 8 marks down. If dividing the interval by three results in a fraction of a mark, then the threshold is normally rounded down.

June 2005 GCE A LEVEL MARK SCHEME MAXIMUM MARK: 30 SYLLABUS/COMPONENT: 9700/05 BIOLOGY Paper 5 (Practical Test A2)

Page 1 Mark Scheme Syllabus Paper GCE A LEVEL – JUNE 2005 9700 5 © University of Cambridge International Examinations 2005 Question Expected Answers Marks Additional Guidance 1 (a) tubes 2 and 3 in headers; time in header; units shown in header; dark time > light time; 1 1 1 1 Accept tables showing cell results or showing only the time taken for reduction to occur. (b) three from light causes chlorophyll to donate electron; DCPIP (absorbs electron and) is reduced; ref to NADP/reduced NADP; change only occurs in presence of light; Max 3 ORA (c) slow rate of reaction reduce enzyme activity; some qualification e.g. kinetic energy; ref to autolysis; 3 max (d) maintain constant pH; 1 OWTTE (e) maintain suitable osmotic equilibrium; 1 OWTTE (f) filter or centrifuge; solutions constant distance from lamp; better light control; constant temperature; use colorimeter; repeat experiment 3 max 15 2 (a) 4.5:1; accept 9:2 2 1:4.5 or 2:9 = 1 mark (b) (i) too many red/too few white; no grid or accurate counting method; 1 1 (ii) ratio of red to white much greater; 1 (c) (i)- (iii) eight from: correct cells drawn; proportions i.e. rbc smallest or same as lymphocyte and phagocyte largest; quality clear single lines; large lobed nucleus in phagocyte; granular cytoplasm in phagocyte; very large spherical nucleus in lymphocyte; two correct labels; 8 (iv) between 7 and 11; µm; 1 1 15 Paper 30