Biology Practice Paper Essay
UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level .c rs om *0485738200* BIOLOGY Paper 2 Structured Questions AS Candidates answer on the Question Paper. Additional Materials: Electronic calculator Ruler (cm/mm) 9700/21 October/November 2009 1 hour 15 minutes 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. You may use a soft pencil for any diagrams, graphs or rough working.
Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer all questions. 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 3 4 5 6 Total This document consists of 13 printed pages and 3 blank pages. DC (CW/CGW) 13011/4 © UCLES 2009 [Turn over 2 Answer all the questions. For Examiner’s Use 1 During an immune response, plasma cells secrete antibody molecules. Fig. 1. 1 s a diagram of an antibody molecule. The diagram is not complete. Fig. 1. 1 (a) (i) (ii) (iii) Draw a circle around a variable region. Draw in and label the position of the disulfide bonds in the molecule.   Explain the importance of disulfide bonds in protein molecules, such as antibodies. …………………………………………………………………………………………………………………. For Examiner’s Use © UCLES 2009 9700/21/O/N/09 [Turn over 4 2 Amylase is an enzyme that catalyses the hydrolysis of starch. A student investigated the effect of pH on the activity of the enzyme. Eight test-tubes were set up each containing 5 cm3 of the same concentration of amylase solution but in buffer solutions of different pH values.
The test-tubes were left in a water-bath at 30 °C for 10 minutes. After 10 minutes, 5 cm3 of a starch suspension at 30 °C was added to each test-tube. Immediately, the student took a sample from each test-tube and tested the reaction mixture for the presence of starch. Samples were then taken every minute for 10 minutes and tested in the same way. The student’s results are shown in Table 2. 1. Table 2. 1 time / min 0 ? ? ? ? ? ? ? ? 1 ? ? ? ? ? ? ? ? 2 ? ? ? ? ? ? ? ? 3 ? ? ? ? ? ? ? ? 4 ? ? ? ? ? ? ? ? 5 ? ? ? ? ? ? ? ? 6 ? ? ? ? ? ? ? ? 7 ? ? ? ? ? ? ? ? 8 ? ? ? ? ? ? ? ? 9 ? ? ? ? ? ? ? ? 10 ? ? ? ? ? ? ? For Examiner’s Use pH 2. 0 3. 0 4. 0 5. 0 6. 0 7. 0 8. 0 9. 0 key ? = starch present ? = starch absent (a) Describe how the student would test for the presence of starch.