Cambridge A Level Biology 9700 — 2005 May/June Paper 3 · Variant 1

This document consists of 7 printed pages and 1 blank page. SP (CW/KS) S84445/4 © UCLES 2005 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level BIOLOGY 9700/03 Paper 3 Practical Test AS May/June 2005 1 hour 15 minutes Candidates answer on the Question Paper. Additional Materials: As listed in Instructions to Supervisors. READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name in the spaces provided at the top of this page. 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 40 minutes on Question 1 and 35 minutes on Question 2. Centre Number Candidate Number Name For Examiner’s Use 1 2 Total

2 9700/03/M/J/05 1 You are required to investigate the effect of a bacterial digestive enzyme on protein. You are provided with one test-tube containing a solution labelled S1 and three test-tubes containing a solution labelled S2. Both solutions, S1 and S2, contain the bacterial enzyme at pH7, but solution S1 has been boiled. You are also provided with four lengths of glass capillary tubing that contain solidified egg white. Egg white contains the protein albumin. Place one length of capillary tubing into each test-tube as shown in Fig. 1.1. Avoid getting any solution on your skin. Fig. 1.1 Place the test-tube labelled S1 into a water bath at approximately 35 °C. Place one of the test-tubes labelled S2 into a water bath at approximately 45 °C. Place two of the test-tubes labelled S2 into a water bath at approximately 35 °C. To one of the 35 °C test-tubes labelled S2 add dilute acid drop by drop until it has a pH of less than 3. Count the drops. Use universal indicator paper to check the pH. Label this test- tube pH3. Add the same number of drops of distilled water to each of the other three test-tubes. (a) (i) Explain why is was necessary to add the same number of drops of distilled water to the other three test-tubes. … …[1] Leave the solutions for at least thirty minutes. While you are waiting, you may start question 1 (b). For Examiner’s Use © UCLES 2005

3 9700/03/M/J/05 [Turn over (ii) Gently shake each test-tube. Carefully examine the capillary tubes, still within the test-tubes, in front of the dark coloured card. Draw what you see in the boxes below. [2] (iii) Give a detailed explanation of your results. … … … … … …[3] capillary tube in S2 at 35 °C at <pH3 capillary tube in S2 at 45 °C at pH7 capillary tube in S2 at 35 °C at pH7 capillary tube in S1 at 35 °C at pH7 For Examiner’s Use © UCLES 2005

4 9700/03/M/J/05 (b) A student carried out a similar experiment for a longer period of time, using a range of buffer solutions. The results are shown in Table 1.1. Table 1.1 (i) Plot a graph of the pH against one of the other variables on the grid below. [3] For Examiner’s Use © UCLES 2005 pH length of egg white remaining / mm length of clear tube / mm 6 20 10 7 17 13 8 15 15 9 23 7 10 26 4 11 28 2

5 9700/03/M/J/05 [Turn over (ii) Explain why the rate of reaction changes with pH. … … … …[3] (c) Explain how the experiment could be modified to determine the effect of enzyme concentration on the rate of the reaction. … … … … …[3] [Total : 15] For Examiner’s Use © UCLES 2005

6 9700/03/M/J/05 2 K1 is a stained transverse section through part of a dicotyledonous plant. Examine the specimen using the low-power of your microscope. (a) (i) Draw a large, labelled, plan diagram to show the distribution of tissues. [5] (ii) State from which part of the plant the section was taken. Explain your answer. … … …[2] For Examiner’s Use © UCLES 2005

7 9700/03/M/J/05 (iii) Make a high-power drawing to show a group of four cells from the region nearest the centre of the specimen. Labels are not required. [3] [Total : 10] [Paper total : 25] For Examiner’s Use © UCLES 2005

8 9700/03/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 Subsidiary and Advanced Level MARK SCHEME for the June 2005 question paper 9700 BIOLOGY 9700/03 Paper 3 (Practical Test AS), maximum raw mark 25 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 3 25 19 17 12 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 AS/A LEVEL MARK SCHEME MAXIMUM MARK: 25 SYLLABUS/COMPONENT: 9700/03 BIOLOGY Paper 3 (Practical Test AS)

Page 1 Mark Scheme Syllabus Paper AS/A LEVEL – JUNE 2005 9700 3 © University of Cambridge International Examinations 2005 Question Expected Answers Marks Additional Guidance 1 (a) (i) to ensure same degree of dilution/ concentration of (enzyme) 1 (ii) top left full tube; top right = medium amount of change; bottom left = most change; bottom right = some but little change; 2 3 or 2 correct = 1 mark (iii) S1 enzyme denatured; correct explanation of denaturing; increased kinetic energy at 45 oC; explanation for acid reducing rate of reaction; 3 max (b) (i) length of clear area on y axis; plots correct; line of best fit (dot to dot or smooth curve through all points); 1 1 1 if length of albumin plotted against length of clear tube then max 1 Must use more than half of grid for axis mark Reject extrapolations (ii) correct ref to optimum pH; ref to changes active site; ref to detail cause of change; 1 1 1 e.g. bonds/3D/tertiary (c) three from serial dilution OWTTE; range of at least five enzyme concentrations; explanation of control; keep variables constant or example e.g. constant temp or pH/run for set time; reliability or validity comment; Max 3 15 2 (a) (i) five from: corner vascular bundle bigger than other vb; 3 layers of cells represented plus cambium; no individual cells represented; four sided shape; xylem in corner labelled; phloem labelled correctly; parenchyma labelled correctly; sclerenchyma on outer edge of VB labelled; collenchyma in corners labelled; Max 5 slide is TS of lamium stem (ii) stem; vascular tissue/strengthening tissue near edges/pith/vascular tissue in bundles/phloem outside xylem/cambium or trichomes present; 1 1 AVP

Page 2 Mark Scheme Syllabus Paper AS/A LEVEL – JUNE 2005 9700 3 © University of Cambridge International Examinations 2005 (iii) three from: quality of drawing i.e. clear single lines; four cells similar in shape and size; thin cell walls, one line or two close together; 5-8 sided polygonal cells; air spaces/not tight fit; Max 3 10 Paper 25