2025 JPJC H2Bio PE P2 (A)

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 19 printed pages and 1 blank page.

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] Fluid: 1. “Fluid” means that the phospholipids and proteins are free to move within the membrane ; 2. Phospholipids are held by weak hydrophobic interactions and hence move about rapidly by diffusion in their own layers ; 3. Unsaturated fatty acid tails of phospholipids have kinks that keep the molecules from packing together, enhancing membrane fluidity ; (least important) Mosaic: 4. Proteins are embedded within the phospholipid bilayer in a random manner ; (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] 1. phospholipid with a head and two tails ; 2. bilayer shown ;

3 JPJC/JC2 H2 Biology/PE/2025 [Turn over (c) (i) Suggest the components present in the surfactant. ................................ ................................ ................................ .......