2022 J2 ASRJC H2 Biology Prelims Paper 2 (Ans)

ASRJC BIOLOGY DEPT 9744//2022/J2PRELIM/P2 [Turn over H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 ANSWERS 2022 JC2 PRELIMINARY EXAMINATIONS CANDIDATE NAME CLASS INDEX NUMBER BIOLOGY 9744/02 PAPER 2 SHORT STRUCTURED QUESTIONS Candidates answer on the Question Paper. No Additional Materials are required. 13 SEPTEMBER 2022 TUESDAY 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. Answer all questions. 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 13 printed pages and 1 blank page For Examiner’s Use 1 / 10 2 / 11 3 / 9 4 / 10 5 / 10 6 / 10 7 / 10 8 / 10 9 / 10 10 / 5 11 / 5 Total /100

ASRJC BIOLOGY DEPT 9744//2022/J2PRELIM//P2 Answer all the questions. 1 Chitin, the second most abundant organic polymer after cellulose on Earth, is found in the cell walls of fungi and the exoskeleton of insects. Similar to cellulose, chitin is a structural polysaccharide. Chitin consists of N-acetylglucosamine. Fig. 1.1 shows the structure of chitin. Fig. 1.1 (a) With reference to Fig. 1.1, (i) name the covalent bond between two monomers in a chitin molecule and describe how this bond is formed. 1. Monomers are linked by β (1,4) glycosidic bonds; 2. Which is formed via a condensation reaction, with loss of 1 water molecule per bond formed; 3. between a hydroxyl/OH group on carbon atom 1 of one N- acetylglucosamine and a hydroxyl/OH group on carbon atom 4 of another N-acetylglucosamine; 4. every alternate/successive N-acetylglucosamine monomer has to be rotated by 180°/ inverted with respect to one another , so that the –OH groups on carbon atoms 1 and 4 to line up alongside each other during condensation. [3]

3 ASRJC BIOLOGY DEPT 9744//2022/PRELIM/P2 [Turn over (ii) explain how the structure and property of chitin are related to its role as a structural polysaccharide in fungi and insects. 1. Alternate N-a