RI 2023 Prelim H2 Bio P2 QP

© RI 2023 Preliminary Examination 9744/02 [Turn over RAFFLES INSTITUTION 2023 Year 6 Preliminary Examination Higher 2 BIOLOGY 9744/02 Paper 2 Structured Questions 21st September 2023 2 hours Candidates answer on Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your index number, CT group & name in the spaces at the top of this page. Write in a dark blue or black pen. You may use a HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. Answer all questions in the spaces provided on the Question Paper. The use of an approved scientific calculator is expected, where appropriate. 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. This document consists of 27 printed pages and 1 blank page CIVICS GROUP CANDIDATE NAME INDEX NUMBER 3 S 0 3 2 For Examiner’s Use 1 / 10 2 / 12 3 / 9 4 / 11 5 / 10 6 / 11 7 / 10 8 / 13 9 / 8 10 / 6 Total / 100 Raffles Institution Internal Examination

2 © RI 2023 Preliminary Examination 9744/02 For Examiner’s Use [Turn over Section A Answer all the questions in this section. 1 Fig. 1.1 is a transmission electron micrograph of part of an animal cell. Fig. 1.1 (a) Name the structures A, B and C. A…………………………………………………………………………………………………………… B…………………………………………………………………………………………………………… C……………………………………………………………………………………………………...…[2] (b) Name one organelle that would also be present in a prokaryotic cell. …………………………………………………………………………………………………………..[1] B Golgi apparatus plasma membrane Golgi apparatus B A C nucleus

3 © RI 2023 Preliminary Examination 9744/02 [Turn over For Examiner’s Use (c) Describe the structure of B and its role. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………..[4] (d) Sodium ions cross cell surface membranes using facilitated diffusion or active transport. Explain why sodium ions cross cell surface membranes by these mechanisms and not by simple diffusion. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………….. …………………………………………………………………………………………………………..[3] [Total: 10]

4 © RI 2023 Preliminary Examination 9744/02 For Examiner’s Use [Turn over 2 Staphylococcus aureus (S. aureus) is a bacterium that causes disease in humans. The bacterium is able to enter the bloodstream via open wounds or mouth sores. It divides rapidly by binary fission, entering human tissues and causing multiple infections such as pneumonia and endocarditis. Fig. 2.1 shows how S. aureus divides by binary fission. Fig. 2.1 (a) Describe two differences in DNA behaviour during binary fission in a prokaryotic cell and mitosis in a eukaryotic cell. .………………….………………..……………………………….……………………………………… ………………………….………………………………………….……………………………………… .………...…………………….…………………………………….……………………………………… ……………………………………..……………………………………………………………………[2] Scientists carried out an investigation to find the most effective concentration of an antibiotic to treat an S. aureus infection. The scientists put equal volumes of a culture of S. aureus in five flasks. • For the control flask, sterile distilled water was added. • To the remaining four flasks, different concentrations of the antibiotic was added. The scientists incubated all the flasks at 35° C for 3 hours. They then estimated the number of living bacteria in each flask. (b) Suggest why the flasks were incubated at 35°C. …………………………..………………………………………….……………………………………... …………………………………..………………………………………………………………………[1]

5 © RI 2023 Preliminary Examination 9744/02 [Turn over For Examiner’s Use Fig. 2.2 is a graph which shows the results of the investigation. Fig. 2.2 (c) A student concluded from these results that an antibiotic dose equivalent to 50 μg cm-3 will effectively treat infections caused by S. aureus. Evaluate his conclusion. ………………….………………………………………………….……………………………………… ……………………….…………………………………………….……………………………………… …………………………….……………………………………….……………………………………… ………………………………….………………………………….……………………………………… ……………………………………….…………………………….……………………………………… ……………………………………………..……………………………………………………………[3] (d) The antibiotic used in the experiment was penicillin. Penicillin acts as an inhibitor to an enzyme found in S. aureus. (i) Name the enzyme inhibited by penicillin. ……………………………………………………………………………………………………[1] (ii) Describe how penicillin inhibits this enzyme. ……………………………………………………………….……………………………………… ……………………………………………………………….……………………………………… ……………………………………………………………….……………………………………… ……………………………………………………………………………………………………[2] number of living bacteria remaining after 3 hours (x 106) concentration of antibiotic / µg cm-3

6 © RI 2023 Preliminary Examination 9744/02 For Examiner’s Use [Turn over (iii) Explain how penicillin reduces bacterial growth as a result of this inhibition. ……………………………………………………………….……………………………………… ……………………………………………………………….……………………………………… ……………………………………………………………….……………………………………… ……………………………………………………………….……………………………………… ……………………………………………………………….……………………………………… ……………………………………………………………………………………………………[3] [Total: 12] 3 Hurler syndrome is an autosomal recessive condition caused by a mutation in the IDUA gene. This gene, when expressed normally, codes for the enzyme iduronidase which breaks down waste in cells. When this enzyme is absent or insufficient, toxic waste accumulates in the cells, causing symptoms of Hurler syndrome. Symptoms of Hurler syndrome are life threatening and affects an estimated 1 in every 100,000 newborns and affects males and females equally. A study was done to investigate the use of stem cells for the treatment of Hurler syndrome. Nine mice homozygous for the mutant IDUA gene were involved in this study and were divided into three experimental groups. Table 3.1 shows the treatments the mice were given. Table 3.1 experimental group treatment SC-X Mice were injected with stem cells taken from a mouse that was not affected by the disease. Mice in this group had their immune systems suppressed. SC-S Mice were injected with their own stem cells to which the normal, dominant, allele of IDUA gene had been added by means of a viral vector. SC-O untreated controls (a) (i) What are the unique features of stem cells that made them suitable to treat this disease? ……………………………………………………………….……………………………………… ……………