2025 ASRJC H2 Biology Prelims Paper 4 QP

ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P4 H2 ANDERSON SERANGOON JUNIOR COLLEGE HIGHER 2 2025 JC2 PRELIMINARY EXAMINATION CANDIDATE NAME CLASS 2 5 / INDEX NUMBER BIOLOGY 9744/04 Paper 4 Practical Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. 28 August 2025 Thursday 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your name and class 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 23 printed pages and 1 blank page. Shift Laboratory For Examiner’s Use 1 / 28 2 / 13 3 / 14 Total / 55 %

2 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P4 Answer all questions. 1 Amylase is an enzyme that catalyses the hydrolysis of starch to maltose. You will investigate the effect of the concentration of amylase on the time taken to completely hydrolyse starch to maltose. Iodine solution turns from an orange-brown colour to a blue-black when starch is present. The course of the reaction can be monitored by sampling at intervals and using iodine solution to test for the presence of starch. The end -point is when all the starch has been hydrolysed by amylase. At the end-point, the colour of the iodine solution may be slightly different compared to the colour of the original iodine solution and there may be some specks of blue -black. These specks of blue-black can be ignored. (a) Describe and explain how reducing the concentration of amylase is expected to affect the time taken to reach end-point. …………………………………………………………...……….…………………………………… ………………………………………...………………………….…………………………………… …………………..…………………….……….……………………………………………………… …………………………..……………….………………….………………………………………… ………………………………………………………………………………………………………[2] You are provided with: • 200 international units dm-3 (U dm-3) amylase solution A, in a container labelled A • distilled water W, in a container labelled W • starch solution S, in a container labelled S • iodine solution in a container labelled iodine. Amylase solution A is an irritant and iodine solution is a stain. Suitable eye protection should be worn . If A or iodine solution comes into contact with your skin, wash it off immediately under a tap. (b) (i) You will carry out proportional dilutions of the 200 U dm-3 amylase solution A to obtain a range of concentrations in which the concentration of the amylase is reduced by 50 U dm-3 between each successive dilution. You will prepare 10.0 cm3 of each concentration, using A and W. Complete Table 1.1 to show how you will prepare the different concentrations of amylase solution.

3 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P4 [Turn over Table 1.1 Concentration of amylase / U dm-3 volume of A / cm3 volume of W / cm3 200 0 [2] Read steps 1–13 before starting the investigation. Proceed as follows. 1 Prepare the concentrations of amylase solution as shown in Table 1.1, in the containers provided. 2 Label test-tubes with the concentrations of amylase solution prepared in step 1. Before proceeding further, use the container labelled hot water to collect approximately 300 cm3 of hot water from where it is provided in the laboratory. You should also fill the container labelled tap water with water from a tap. 3 The enzyme's optimum temperature is 35°C. Using the hot water and tap water that you have collected, set up a water-bath at 35°C in the beaker labelled water-bath. You will need to maintain this temperature throughout the investigation. 4 Label the white tile as shown in Fig. 1.1. The numbers indicate the sampling times in seconds. Fig. 1.1

4 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P4 5 Put one drop of iodine solution on the white tile at each labelled sampling time, as shown in Fig. 1.1. 6 Put 3.0 cm3 of S into each of the test-tubes labelled in step 2. 7 Put 2.0 cm3 of 200 U dm-3 amylase solution into the test-tube labelled with this concentration. Use a glass rod to mix the amylase solution with S. Proceed to step 8 without delay. 8 Put the test-tube with the mixture of amylase solution and S into the water-bath prepared in step 3. Start timing immediately. 9 After 15 seconds, and every 15 seconds from then on, use the glass rod to transfer one drop of the mixture from the test -tube onto the drop of iodine solution on the white tile that corresponds to the correct sampling time. After each transfer, clean the g lass rod with a paper towel. 10 Continue testing further drops of the mixture from the test-tube, as described in step 9, until the end-point is reached. If the end-point has not been reached within 180 seconds, do not test further samples from the test-tube. 11 Record, in (b)(ii), the time taken to reach the end-point. If the end-point has not been reached after 180 seconds, record the result as 'more than 180' and note the colour of the mixture in brackets, e.g. 'more than 180 (blue-black)’. 12 Rinse the white tile with running water from a tap and wipe dry with a paper towel. If the labels are no longer visible, you will need to label the white tile again, as shown in Fig. 1.1. 13 Repeat steps 7–11 with each of the other concentrations of amylase that you prepared in step 1. Before testing each of the concentration of amylase, make sure that the white tile is clean by carrying out step 12.

5 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P4 [Turn over (ii) Record your results in an appropriate table. [4]

6 ASRJC BIOLOGY DEPT 9744/2025/J2PRELIM/P4 The urine of healthy people contains a low concentration of amylase. Some medical conditions can cause variation in the concentration of amylase in urine. Amylase concentrations in the urine can be tested as part of a health check. You will be testing solutions that represent urine samples collected from three different people as part of a health check, U1, U2 and U3. They are not actual urine samples. The samples are provided in containers labelled U1, U2 and U3. You are required to test each sample and estimate the concentration of amylase in each sample. Read steps 14–18. Proceed as follows. 14 Ensure that the water-bath prepared in step 3 is still at a temperature of 35 °C. You will need to maintain the water-bath at this temperature. 15 Label three clean test-tubes U1, U2 and U3. 16 Put 3.0 cm3 of S into each of the test-tubes labelled in step 15. 17 Repeat steps 7–10 with each of the unknown concentrations of amylase: U1, U2 and U3. Before testing each of the unknown concentrations of am