ASRJC 2023 JC2 H2 Biology Prelims Paper 3 (Ans)

ASRJC BIOLOGY DEPT 9744//2023/J2PRELIM/P3 [Turn over H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 ANSWERS 2023 JC2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS INDEX NUMBER BIOLOGY 9744/03 PAPER 3 LONG STRUCTURED AND FREE RESPONSE QUESTIONS Candidates answer on the Question Paper. No Additional Materials are required. 15 SEPTEMBER 2023 FRIDAY 2 HOURS READ THESE INSTRUCTIONS FIRST Write your name and class on all the work you hand in. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graph. Do not use paper clips, highlighters, glue or correction fluid. Section A Answer all questions in the spaces provided on the Question Paper. Section B Answer any one question 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 19 printed pages and 1 blank page For Examiner’s Use 1 / 30 2 / 10 3 / 10 4 /5 / 25 Total / 75

ASRJC BIOLOGY DEPT 9744/2023/J2PRELIM/P3 Section A Answer all the questions in this section. 1 Proteins must fold into defined three-dimensional structures to gain functional activity. In the cellular environment, newly synthes ised polypeptides are at great risk of misfolding and aggregation. Cells hence engage proteins called chaperones to assist in protein folding. These chaperones have two roles: 1. They bind to proteins to promote folding. 2. They direct misfolded polypeptides for degradation in the cytosol. However, polypeptides that are in the midst of folding may be mistaken by chaperones as misfolded proteins and then directed fo r degradation. Therefore, protein folding needs to be completed quickly to prevent premature degradation. A recently discovered endoplasmic reticulum (ER) protein complex called S-E complex was found to delay premature degradation of polypeptides that are in the midst of folding. In its absence, approximately 30% of newly synthesised proteins that could otherwise fold correctly are degraded. Fig. 1.1 illustrates these processes. Fig. 1.1

3 ASRJC BIOLOGY DEPT 9744/2023/J2PRELIM/P3 [Turn over With refer