2026 TJC JC2 Prelim H2 Biology P2 (Ans)

1 [TURN OVER READ THESE INSTRUCTIONS FIRST Write your Center number, index number and name in the spaces at the top of this page. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. 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 any working or if you do not use appropriate units. TEMASEK JUNIOR COLLEGE 2026 JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME ANSWERS CENTRE NUMBER S INDEX NUMBER BIOLOGY 9477/02 Paper 2 Structured Questions PART I 28 AUGUST 2026 2 hours Candidates answer on the Question Paper. No Additional Materials are required. The number of marks is given in brackets [ ] at the end of each question or part question. For Examiner’s Use 1 / 10 2 / 10 3 / 8 4 / 8 5 / 7 6 / 15 7 / 10 8 / 8 9 / 8 10 / 6 Total / 90 This document consists of 11 printed pages and 1 blank page.

2 Answer all questions. 1 A plasma B lymphocyte is involved in the adaptive immune response. In an investigation, plasma B lymphocyte were grown in a culture medium containing fluorescent - tagged amino acids. Samples of these cells were taken and the level of fluorescence in three organelles was measured. Table 1.1 shows the results of this investigation. Table 1.1 time after fluorescent-tagged amino acids were added to the culture medium / min level of fluorescence present / arbitrary units (a.u.) organelle A organelle B organelle C 1 21 120 6 20 52 88 6 40 86 39 8 60 71 23 15 90 50 27 28 120 23 11 51 (a) Suggest a reason for using amino acids that were fluorescent-tagged. [1] To track the movement of the amino acids/OWTTE Idea of measure + location/position R: distinguish between tagged and not-tagged amino acids, how will you see the non- tagged? R: activity of amino acid, its not a protein (b) State and explain how amino acids enter the cell. [2] 1. Facilitated diffusion 2. All amino acids are polar/charged due to positively-charged amino and negatively- charged carboxyl groups, 3. They require channel/transport/membrane proteins with a hydrophilic channel to shield the amino acids from the hydrophobic core of phospholipid bilayer (c) With reference to Table 1.1, (i) identify organelle A and B; [2] A: Golgi apparatus/body B: Rough endoplasmic reticulum; R: ribosome

3 [TURN OVER (ii) explain the changes in the level of fluorescence in organelle B. [2] 1. [QF] From 1 min to 120min, level of fluorescence decreases from 120 a.u. to 11 a.u.. 2. Ribosomes on rough endoplasmic reticulum that are the site of protein synthesis. A: protein synthesis/translation at ribosomes R: RER is site of protein synthesis, no mention of ribosomes 3. Fluorescent tagged amino acids are used to synthesise fluorescent tagged proteins that eventually transported to GA/bud off in an ER vesicle. (d) Describe how the Golgi apparatus functions in the synthesis of glycoproteins such as antibodies. [2] Any 4 1. Endoplasmic reticulum (ER) vesicle containing polypeptide/protein/antibody fuses with cis face of Golgi apparatus (GA); R: endoplasmic vesicle 2. GA modifies protein by attaching polysaccharide/carbohydrate chain to protein A: sugar group/molecule/glucose, R:hydrocarbon chain 3. via glycosylation; R: wrong spelling, especially glycosidation 4. Glycoprotein is packaged into Golgi vesicle and moves through the GA via budding off from one cisternae and fusing with another cisternae 5. Glycoprotein is packaged into a secretory vesicle and buds off from trans face of GA. No need to mention fluorescent, since no reference to figure needed from question. (e) Name the organelle where class switching occurs in the plasma B lymphocyte. [1] Nucleus [Total: 10]

4 2 Osteogenesis imperfecta (OI) is a genetic disorder of connective tissues caused by an abnormality in the synthesis or processing of type I collagen, a protein crucial for bone strength. It is also called brittle bone disease. It is characterised by an increased susceptibility to bone fractures. While primarily affecting bones, OI can impact other connective tissues like skin and ligaments. Fig 2.1 below shows amino acids that are found in collagen. Fig 2.1 (a) Select two amino acids from Fig. 2.1 that are most commonly present in collagen. Draw in the space below to show they are joined during the synthesis of collagen. Any 6 1. Glycine 2. and proline 3. Circle OH and H; must be dotted/dashed line 4. Arrow + labelled condensation reaction 5. Final dipeptide 6. Water molecule 7. “catalysed by peptidyl transferase” with arrow Award MP 3, 4, 6 and 7 regardless of chosen amino acids. [3] arginine glycine proline serine

5 [TURN OVER (b) Explain in the terms of the property of the amino acid R groups, why a substitution mutation of glycine to arginine results in a more severe case of brittle bones than substitution with serine. [3] 1. Glycine’s R group is a H atom, which is small enough to fit into the center of the triple helix 2. Allowing for close association of the three polypeptide chains/polypeptide chains in triple helix; R: tropocollagen/triple helix 3. Arginine has a larger/bulkier R group than Serine OR Serine has a smaller/less bulky R group than Arginine R: polarity differences. Arginine and Serine’s R groups are both polar. 4. Thus, the three polypeptide chains are less closely associated when glycine is replaced by arginine than by serine OR Thus, the three polypeptide chains are more closely associated when glycine is replaced by serine than by arginine/ OWTTE A: triple helix not as tightly wound/ helical structure disrupted less R: further association. fUrther means additional. fArther means longer distance. Regardless not a term recommended. 5. Interchain hydrogen bonds formed are weakened to a larger extent/even fewer interchain hydrogen bonds are formed when glycine is replaced by arginine than by serine OR Interchain hydrogen bonds formed are weakened to a smaller extent/not as few interchain hydrogen bonds when glycine is replaced by serine than by arginine 6. and thus lowers tensile strength to a larger extent when glycine is replaced by arginine than by serine OR and thus lowers tensile strength to a smaller extent when glycine is replaced by serine than by arginine Thus, more fractures. Extent/comparison mentioned CLEARLY either in MP4 or MP5 or MP6

6 (c) Individuals with OI often suffer from ana emia, a disease which is linked to haemoglobin, an important protein found in red blood cells. (i) Table 2.1 lists two proteins found in cells. Complete Table 2.1 by placing a tick () to show whether the feature is present in collagen and / or haemoglobin or a cross (✘) if the feature is absent. Put a tick () or a cross (✘) in every box. Table 2.1 feature collagen haemoglobin globular shape ✘  metal ion ✘  covalent cross-links  ✘ [3] (ii) Suggest why individuals with OI tend to suffer from anaemia. [1] Any one 1. Loss of blood due to injury 2. RBC formation is reduced 3. Less myeloid stem cells 4