2026 RI H2 Biology Prelims P4 Answers

©RI 2026 Preliminary Examination 9477/04 [Turn over RAFFLES INSTITUTION 2026 Year 6 Preliminary Examination Higher 2 BIOLOGY 9477/04 Paper 4 Practical 20th August 2026 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. Answer Question 3(a) on the writing paper provided. 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 15 printed pages and 1 blank page. CIVICS GROUP CANDIDATE NAME INDEX NUMBER 6 S 0 3 2 For Examiner’s Use 1 2 3 Total Shift Laboratory Raffles Institution Internal Examination 2 6

2 ©RI 2026 Preliminary Examination 9477/04 For Examiner’s Use Answer all questions. Question 1 (a) You are advised to read the whole of Question 1(a) before you start. Some fruits such as pineapple, papaya and kiwi fruit, contain the enzyme bromelain which catalyses the hydrolysis of proteins into amino acids. Gelatin is a protein derived from animal tissues and is used in the production of foods such as fruit jellies. When left to cool, warm liquid gelatin will fully set to form a semi-solid gel. You will investigate the effect of different concentrations of the bromelain enzyme extract on the firmness of gelatin. You are required to: ● prepare warm liquified gelatin and a range of bromelain concentrations ● make six test -tubes of warm gelatin with different concentrations of bromelain enzyme already added ● observe the consistency of the gelatin gel and measure the volume of liquified gelatin after 10 minutes of incubation in an ice-bath ● perform the Biuret’s test on the liquified gelatin You should wear eye protection and gloves when carrying out the investigation. Care should be taken when using hot water. Proceed as follows. 1 You will carry out a serial dilution of pure bromelain extract B1 to reduce the concentration of bromelain solution by a factor of 2 between each of the four successive dilutions to obtain B2, B3, B4 and B5. You are required to make sufficient volume of each bromelain solution so that, once the serial dilution has been completed, there is at least 3.0 cm3 of each concentration prepared. (i) Complete Table 1.1 to show how you will use the pure bromelain extract, B1, to make B2, B3, B4 and B5. Table 1.1 pineapple bromelain solution B1 B2 B3 B4 B5 percentage concentration of pineapple bromelain solution 100.00 50.00 25.00 12.50 6.25 percentage concentration of pineapple bromelain solution to be diluted 100.00 50.00 25.00 12.50 volume of pineapple bromelain solution to be diluted/ cm3 10.0 (A: 5.0) 10.0 (A: 5.0) 10.0 (A: 5.0) 10.0 (A: 5.0) volume of distilled water W to make the dilution/ cm3 10.0 (A: 5.0) 10.0 (A: 5.0) 10.0 (A: 5.0) 10.0 (A: 5.0) 1. Correct volumes and concentrations; 2. Correct decimal place (dp) for volume (1 dp) and concentration (2dp);

3 ©RI 2026 Preliminary Examination 9477/04 [Turn over For Examiner’s Use [2] 2 Prepare bromelain solutions B2, B3, B4 and B5 in the specimen tubes provided, as shown in Table 1.1. 3 Label 6 test-tubes B1, B2, B3, B4, B5 and U with a marker. 4 Use a clean 1 cm 3 syringe to transfer 1.0 cm3 of B1 from the specimen tube to the test-tube labelled B1. Place the test-tube on the test-tube rack. 5 Wash the 1 cm3 syringe thoroughly using tap water from the container labelled for washing. 6 Repeat steps 4 and 5 by transferring 1.0 cm 3 of B2, B3, B4, B5 and U to their respective test-tubes. 7 Add all of the gelatin powder in the specimen tube labelled G into a 100 cm3 beaker. 8 Collect approximately 100 cm3 of hot water using the container labelled hot water. 9 Measure the temperature of the hot water using a thermometer to check that it is between 50°C to 60°C. Record the temperature of the hot water here. Temperature of hot water: ……………………………………………………………….. 10 Pour the hot water directly into the 100 cm3 beaker containing G, until it reaches the 100 cm3 mark. 11 Use a glass rod to mix the gelatin and hot water gently, so as to minimise the formation of air bubbles. Stir for at least 2 minutes to allow the gelatin powder to dissolve completely and form a homogenous gelatin mixture. 12 To a 250 cm 3 beaker, add crushed ice until approximately the 200 cm 3 mark. This will be the ice-bath that you will use in step 14. 13 Use a syringe to draw up 8.0 cm3 of the gelatin mixture. Add the gelatin mixture into the test-tube labelled B1. Position the syringe so that the nozzle touches the side of the test-tube. 14 Gently push the plunger of the syringe so that the mixture runs slowly down the side of the test-tube to the bottom. Start the stop-watch immediately and put the test- tube into the ice-bath, keeping it upright. Leave the test-tube in the ice-bath for 10 minutes. Use a thermometer to check that the temperature is below 10°C. Leave the stop-watch running throughout the rest of the investigation. 15 Wait for 30 seconds then repeat steps 13 and 14 for the test-tube labelled B2. 16 At every 30 second interval, repeat steps 13 and 14 for B3, B4, B5 and U until all six test-tubes are placed in the ice-bath. 17 It is expected the ice will melt over time. If the temperature goes above 10°C, add some crushed ice to the cold ice-water mixture. (ii) Explain the purpose of the 30 second interval in steps 15 and 16. …………………………………………………………………………………………….[2] 1. idea of staggering to allow time to pour gelatin into each test-tube;

4 ©RI 2026 Preliminary Examination 9477/04 For Examiner’s Use 2. so that each test-tube will have the same reaction time/incubation time/to allow 10min in ice bath before an observation is made; 18 During the 10 minute incubation, read steps 1 9 to 24 so that you will know what observations to make and data to collect once the incubation period is up. 19 Prepare a table to record your results at (a)(iii). 20 Use a mark