JPJC 2023 JC2 H2 Prelim P4 ANS

9744 / 04 [Turn over NAME : CLASS : JURONG PIONEER JUNIOR COLLEGE JC2 Preliminary Examination 2023 BIOLOGY Higher 2 9744/04 17 August 2023 Paper 4 Practical 2 hours 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions READ THESE INSTRUCTIONS FIRST Write your class, index number and name 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 Shift Laboratory For Examiner’s Use 1 2 3 Total This document consists of 16 printed pages.

2 JPJC/JC2 H2 Biology/Prelims/2023 Answer all questions. 1 There are molecules on the surface of yeast cells which cause the cells to stick together. When a yeast suspension is placed in a test-tube some of the cells sink slowly to the bottom. (a) (i) Show clearly on Fig. 1.1 what you would expect the contents of the test-tube to look like after 10 minutes. You will gain marks for clear annotations. Fig. 1.1 [2] 1. Line draw level with half -way mark + more yeast drawn towards bottom of tube or another line to show a separate region ; 2. One annotation/label/description e.g. yeast cells sink ; You are required to investigate the effect of the independent variable, pH, on the sedimentation of a yeast cell suspension over a period of 10 minutes. (ii) State the time intervals you will use and what you will use the graph paper scale to measure. ............................................................................................................................... [2] 1. Uses 10 minutes + o ne/two minutes intervals ; R: if does not divide into 10 e.g. 3 minutes 2. Measures or describes measuring e.g. (use graph paper) to find height + description of what is measured e.g. from halfway mark to top of sediment or bottom of tube to top of sediment/AW ;

3 JPJC/JC2 H2 Biology/Prelims/2023 [Turn over You are provided with: • a suspension of yeast cells, Y, in a beaker labelled Y • calcium chloride solution, C, in a container labelled C • buffer pH 3, pH 4, pH 5 and pH 6 in containers labelled pH 3, pH 4, pH 5 and pH 6. Proceed as follows. 1 Label one test-tube for each pH. 2 Use the marker provided to mark a line half -way along the length of each test -tube as shown in Fig. 1