2025 NYJC H2 Biology Prelims Paper 4_QP

9744 / H2 Biology / 04 NANYANG JUNIOR COLLEGE PRELIMINARY EXAMINATIONS Higher 2 CANDIDATE NAME CLASS BIOLOGY 9744/04 Paper 4 Practical 28 August 2025 Candidates answer on the Question Paper Additional Materials: As listed in the Confidential Instructions 2 hour 30 minutes READ THESE INSTRUCTIONS FIRST Write your name and CT on all the work you hand in. Give details of the practical shift and laboratory, where appropriate in the boxes provided. Write in dark blue or black pen. You may use an HB pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. 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. Shift Laboratory 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. For Examiner’s Use 1 2 Total This document consists of 20 printed pages. [Turn over H

9744 / H2 Biology / 04 2 Answer all the questions. 1 Yeast cells contain enzymes that break down sugars to release energy. In these reactions carbon dioxide is released. Some of this carbon dioxide dissolves in water forming carbonic acid. The progress of these enzyme -catalysed reactions can be followed by measuring the time taken for an indicator to change colour as carbonic acid is formed. You will investigate the effect of changing the concentration of yeast suspension on the time taken for the indicator to change colour. You are provided with the materials shown in Table 1.1. Table 1.1 labelled contents hazard volume/ cm3 Y 10% yeast suspension none 100 H hydrogencarbonate indicator solution none 50 W distilled water none 100 Note that it is normal for Y to froth over time and the froth may overflow from the container. If any solution comes into contact with your skin, wash off immediately under cold water. It is recommended that you wear suitable eye protection. Read step 1 to step 4. (a) (i) Using Table 1.1 and step 1 to step 4, assess the risk of this procedure as low, medium or high. Give one reason for your answer. risk reason [1] The hydrogencarbonate indicator solution, H, will change colour from red-brown to yellow as carbon dioxide passes through it. To help you identify the end-point (yellow) carry out step 1 to step 4. 1 Put 5cm3 of H into a test-tube. 2 Put a drinking straw into this test-tube. 3 Gently breathe out through the straw so that you are blowing air bubbles through H. 4 Stop blowing when the colour changes to yellow. This is the end-point.

9744 / H2 Biology / 04 3 You will need to use this test-tube for colo