2025 RI H2 Bio Prelim P4 Questions

©RI 2025 Preliminary Examination 9744/04 [Turn over RAFFLES INSTITUTION 2025 Year 6 Preliminary Examination Higher 2 BIOLOGY 9744/04 Paper 4 Practical 22nd August 2025 2 hours 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your index number, CT group 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 a 2B pencil for any diagrams or graphs. Do not use staples, paper clips, highlighters, 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, hand in the Question Paper containing your answers. The number of marks is given in brackets [ ] at the end of each question or part of the question. This document consists of 19 printed pages. CIVICS GROUP CANDIDATE NAME INDEX NUMBER 5 S 0 3 2 For Examiner’s Use 1 2 3 Total Shift Laboratory Raffles Institution Internal Examination

2 ©RI 2025 Preliminary Examination 9744/04 For Examiner’s Use Answer all questions. Question 1 (a) Before you proceed, read carefully through the whole of Question 1(a). You are provided with a blue solution, labelled I, which is alkaline. I is blue because it contains an indicator. Carbon dioxide reacts with I when bubbled into it. When enough carbon dioxide reacts with I , the indicator will change from blue to yellow (even if the solution is cloudy). This is the end-point. Hydrochloric acid, H, can also turn indicator I yellow. If only a small volume of carbon dioxide is bubbled into I then the indicator will remain blue. Hydrochloric acid, H, can then be added slowly until the indicator turns from blue to yellow. (i) What is the expected trend of volume of H that needs to be added to reach end point with increased volume of carbon dioxide that has reacted with indicator, I. …………………………………………………………………………………………….……… …………………………………………………………………………………………….……[1] You are provided with: labelled contents YA yeast cell suspension I alkaline solution (blue) H hydrochloric acid I and H are irritants. Suitable eye protection should be worn. If I or H comes into contact with your skin, wash it off immediately under tap water. You are first required to find the volume of H needed to reach the end -point, when no carbon dioxide has been bubbled into I.

3 ©RI 2025 Preliminary Examination 9744/04 [Turn over For Examiner’s Use Proceed as follows: 1. Put 5 cm3 of I into a test-tube. 2. Use a syringe, containing 2 cm3 of H, to put drops of H into I as shown in Fig. 1.1. Mix well as you add H , until the end- point is reached. You may need to fill the syringe again. Fig 1.1 (ii) Record the volume of H needed to reach the end-point. volume of H ……………………………………………….……[1] Yeast cells release carbon dioxide from some of their metabolic reactions. A student investigated the release of carbon dioxide from a yeast cell suspension, using the apparatus shown in Fig. 1.2. Fig 1.2 The student set up this apparatus and left it for 10 minutes. The student observed that during the 10 minutes the bubbles of carbon dioxide were not released at a constant rate.

4 ©RI 2025 Preliminary Examination 9744/04 For Examiner’s Use (iii) Suggest an explanation for the student’s observation on the rate of release of carbon dioxide. …………………………………………………………………………………………….……… …………………………………………………………………………………………….……[1] You are required to investigate this observation using the apparatus set up as in Fig. 1.2. You will move the delivery tube to different test-tubes containing I, at different times during the 10 minutes. (iv) Decide the length of time you will leave the delivery tube in each test-tube containing I. State the length of time. time……………………………………. [1] (v) State one significant source of error that may occur when the delivery tube is moved from one test-tube to the next. Describe how you will reduce this error. source of error……………………………………………….…………………………….…… description……………………………………………….…………………………….……….. ……………………………………………….…………………………….………………...…[2] Read steps 3 to 10 before proceeding: 3. Put 5 cm3 of I into a test-tube. Repeat for the number of test-tubes you need to use for your times in (a)(iv). 4. Obtain YA by placing the nozzle of a large syringe below any froth on the surface. 5. Put 20 cm3 of YA into the large test-tube. 6. Put the bung containing the delivery tube into the large test-tube. It must be airtight. 7. Put the end of the delivery tube into the first test -tube containing I. Immediately start timing. 8. After the time you decided in (a)(iv), move the delivery tube to the next test -tube containing I. 9. Repeat step 8 for all the test-tubes which you set up in step 3. 10. After removing the delivery tube from the last test-tube, repeat step 2 with any of the test tubes where there is still a blue colour. Unplug the rubber bung from the large test tube after step 10 is completed.

5 ©RI 2025 Preliminary Examination 9744/04 [Turn over For Examiner’s Use Record your results in (vi). For any test-tubes where I is yellow (even if the solution is cloudy) record ‘0’. (vi) Prepare the space below to record your results. [4] (vii) Explain whether your results in (vi) support the student’s observation. …………………………………………………………………………………………….……… …………………………………………………………………………………………….……[1]

6 ©RI 2025 Preliminary Examination 9744/04 For Examiner’s Use (b) Before you proceed, read carefully through the whole of Question 1(b). Yeast cells also contain enzymes that hydrolyse sucrose into reducing sugars, as shown in Fig. 1.3. enzymes in yeast cells sucrose reducing sugars Fig.1.3 You will investigate the activity of the enzymes in yeast cells. To immobilise the yeast cells in sodium alginate beads , yeast and alginate should be in equal proportions. (You will need no more than 20 cm3 of the mixture). Alginate will solidify when released into calcium chloride solution, and should be left in the solution for 5 min. You are provided with the following which you must use: labelled contents YB 15 cm3 yeast cell suspension A 15 cm3 sodium alginate solution C 20 cm3 calcium chloride solution Alginate and calcium chloride are irritants. S