HCI 2023 JC2 9744 H2 Bio Prelim P2 QP (Sharing)

© Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 22S7__ CENTRE NUMBER INDEX NUMBER BIOLOGY Paper 2 Structured Questions Candidates answer on the Question Paper. No Additional Materials are required. 9744/02 21 August 2023 2 hours INSTRUCTIONS TO CANDIDATES There are five question booklets ( I - V) to this paper. Write your name and CT group in the spaces provided at the top of this cover page and on the lines provided at the top of the cover pages of Booklets II, III, IV and V. There are ten questions. Answer all questions in the spaces provided on the Question Paper. INFORMATION FOR CANDIDATES 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. The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for good English and clear presentation in your answers. This document consists of 27 printed pages. For Examiners' Use 1 / 11 2 / 10 3 / 12 4 / 10 5 / 12 6 / 13 7 / 12 8 / 10 9 / 5 10 / 5 Total / 100

2 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 QUESTION 1 Bacterial cells are prokaryotic. The cells of plants are described as eukaryotic. Both the bacterial cell and the plant cell have a cell wall, but the main component of the bacterial cell wall is peptidoglycan and not cellulose. (a) Protoplasts are plant cells that have had their cell walls removed by treatment with enzymes. Scientists often use protoplasts when researching ways to improve the yield of crop plants. Fig. 1.1 is a scanning electronmicrograph of protoplasts of cells from the tobacco plant, Nicotiana tabacum. Fig. 1.1 (a) Explain why scientists keep the protoplasts in a solution that has the same water potential as the cell. [2] (a external solution at same water potential as protoplasts cell surface membrane magnification x256

3 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 2 After protoplast treatment, the cells can be stimulated to synthesise new cell wall material. Fig. 1.2 is at a higher magnification than Fig. 1. 1 and shows a scanning electronmicrograph of part of a protoplast in an early stage of cell wall synthesis. Fig. 1.2 (b) The cellulose microfibrils visible in Fig. 1.2 will form cellulose fibres. Each cellulose molecule is a polymer of β-glucose. (i) Define the term polymer. [1] (ii) Explain how the structure of a cellulose molecule allows for the formation of the cellulose microfibrils and fibres. [3]