2020 HCI Prelim Paper 3 Question Paper

This document consists of 26 printed pages and 2 blank pages. HWA CHONG INSTITUTION C2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 19S CENTRE NUMBER INDEX NUMBER CHEMISTRY Paper 3 Free Response Questions Candidates answer on the Question Paper Additional Materials: Data Booklet 9729/03 15 September 2020 2 hours READ THESE INSTRUCTIONS FIRST Write your name, CT group, centre number and index number clearly in the spaces above. Write in 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. If additional space is required, you should use the pages at the end of this booklet. The question number must be clearly shown. Section A Answer all the questions. Section B Answer one question. The use of an approved scientific calculator is expected, where appropriate. A Data Booklet is provided. 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. No. of sheets of writing paper submitted (write 0 if none) For Examiner’s Use 1 / 25 2 / 16 3 / 19 Circle your option below 4 / 5 / 20 Deductions Total / 80

2 © Hwa Chong Institution 2020 9729/03/C2Prelim 2020 [Turn over Section A Answer all the questions in this section. 1 To date, the COVID-19 pandemic has infected more than 1 8 million people. The disease is caused by the SARS -CoV-2 coronavirus, whose general structure is shown in Fig. 1.1, with some of its parts labelled. Fig. 1.1 For Examiner's use (a) The spike proteins on the surface of the virus’ membrane facilitate the entry of the virus into the host cell. The tripeptide below was obtained from partial hydrolysis of the spike proteins. (i) Draw the structures of the organic products obtained when the tripeptide is hydrolysed completely by heating with H2SO4(aq). [3] (ii) Using one of the products from (i) and the aid of a suitable drawing, explain why it exhibits enantiomerism. [2] (iii) Explain why the virus will no longer be able to enter the host cell if the amino acids in the protein sequence were swapped with their enantiomers. [1] ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… spike protein lipid membrane

3 © Hwa Chong Institution 2020 9729/03/C2Prelim 2020 [Turn over ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………………… ……………………………………………………….………………………………