2025 JPJC H2Bio PE P2 (QP)

9744 / 02 [Turn over NAME : CLASS : JURONG PIONEER JUNIOR COLLEGE JC2 Preliminary Examination 2025 BIOLOGY Higher 2 9744/02 2 September 2025 Paper 2 Structured Questions 2 hours Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your class 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. 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 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. For Examiner’s Use 1 2 3 4 5 6 7 8 9 10 11 Total This document consists of 32 printed pages.

2 JPJC/JC2 H2 Biology/PE/2025 Section A Answer all questions. 1 Alveoli are tiny air sacs in the lungs that are crucial for gas exchange. The walls of alveoli contain some specialised epithelial cells called type II epithelial cells. These cells secrete surfactant, which helps to prevent the alveoli collapsing during breathing. The components of surfactant are synthesised in the rough endoplasmic reticulum and smooth endoplasmic reticulum and then passed to the Golgi body. The surfactant that is produced is stored in secretory organelles called lamellar bodies. The surfactant in the lamellar bodies is released onto the surface of the alveolar epithelium, as shown in Fig. 1.1. Fig. 1.1 (a) The cell surface membrane of type II epithelial cells has a fluid mosaic structure. Describe what is meant by the term fluid mosaic. ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ............................ [3]

3 JPJC/JC2 H2 Biology/PE/2025 [Turn over (b) Each lamellar body is surrounded by a single membrane. Draw a diagram to show the arrangement of phospholipid molecules in the membrane surrounding the lamellar body. [2] (i) Suggest the components present in the surfactant. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [2] (ii) Describe how the surfactant is released from the cell. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [3] (iii) Scientists studying the production and secretion of lung surfactant have discovered that a reduction in cholesterol in the cell surface membrane of type II epithelial cells reduces the secretion of surfactant. Suggest why secretion of surfactant is affected by a reduction in cholesterol in the cell surface membranes of type II epithelial cells. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [2] [Total: 12]

4 JPJC/JC2 H2 Biology/PE/2025 2 Proteins have diverse roles that arise from their three -dimensional structures, which are determined by the sequence of amino acids and the nature of bonds formed between them. The structure-function relationship in proteins is critical to life, and disruption to this relationship may result in diseases. Fig. 2.1 shows two examples of proteins: • G-protein-linked receptors (GPLRs), which are membrane proteins that are involved in majority of cell signalling processes in the body. • Collagen, a fibrous protein that forms structural scaffolds in connective tissues like skin, bone, and tendons. Fig. 2.1 (a) With reference to Fig. 2.1, describe how the bonding and amino acid composition contribute to the shape of each protein. ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ................................ . ................................ ................................ ................................ ............................ [2]

5 JPJC/JC2 H2 Biology/PE/2025 [Turn over (b) (i) Explain how the molecular structure of the G-protein linked receptor relates to its function. ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ........................ ................................ ................................ ................................ ................... [3] (ii) A mutation in the GPLR gene leads to the substitution of a non -polar amino acid for an essential