2023 ASRJC JC2 H2 Biology Prelims Paper 4 (ANS)

ASRJC BIOLOGY DEPT 9744/2023/J2PRELIM/P4 [Turn over H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 2023 JC2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS INDEX NUMBER BIOLOGY 9744/04 Paper 4 Practical 30 August 2023 Wednesday 2 hours 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your name, class and index number 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, 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. 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. This document consists of 15 printed pages and 1 blank page. Shift Laboratory For Examiner’s Use 1 2 3 Total /55

1 ASRJC BIOLOGY DEPT 9744/2023/J2PRELIM/P4 Answer all questions. 1 Plant cells con tain en zymes that catalyse metabolic reactions. Some of these enzymes catalyse the release of oxygen from hydrogen peroxide. A plant extract solution can be produced which will contain these enzymes. When hydrogen peroxide and a plant extract solution are mixed, oxygen is released. The oxygen forms bubbles that make a foam on the surface. You are required to investigat e the effect of pH on the progress of the enzyme-catalysed reactions by: • changing the pH using buffers • measuring the height of the foam produced by the release of oxygen. To follow the progre ss of this reaction, you will nee d to measure the height of foam at different times for a total of 3 minutes. (a) (i) Decide how often you will take these measurements , including the final height of foam at 3 minutes. State the times when you will measure the height of foam. [1] Must state at least 5 timings to measure, at regular intervals → preferred: 30s, 60s, 90s, 120s, 150s, 180s [must] (ii) Fig. 1.1A shows how a test-tube will be set up at the start (0 minutes). Fig. 1.1B shows the test-tube after 3 minutes. Fig. 1.1 The top of the foam may not form an even layer, so you will need to decide where to measure the layer of the foam. Draw a double-headed arrow on Fig. 1.1B to show where you will measure this layer of foam. [1] 1. top and bottom of arrow to