2026 ACJC H2 Biology Prelim P4 MS

This document consists of 16 printed pages. [Turn over] Anglo-Chinese Junior College JC2 Biology Preliminary Examination Higher 2 CANDIDATE NAME FORM CLASS TUTORIAL CLASS INDEX NUMBER BIOLOGY Paper 4 Practical Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. 9477/04 12 August 2026 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your Name, Class and Index number in the spaces 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 Examiners’ use 1 / 23 2 / 9 3 / 18 Total / 50

2 Anglo-Chinese Junior College H2 9477 Paper 4 Preliminary Examination For Examiner Use Answer all questions. 1 Scientists are exploring the use of plant -derived biopolymers for medical applications such as wound dressings, drug delivery systems and surgical implants. Wild-type crops synthesise biopolymers naturally that can be harvested for biomedical applications. Transgenic crops are genetically modified with genes from another organism to enhance polymer production, making them more suitable for large-scale biomedical use. The success of biopolymer synthesis is closely linked to crop growth rates, which are strongly influenced by the rate of photosynthesis. (a) (i) Predict how the rate of photosynthesis in the chloroplast extracts from wild-type crops would compare to that in the transgenic crops. The chloroplast extract from the transgenic crops will have a higher rate of photosynthesis; [1] To test the rate of photosynthesis, the blue dye DCPIP, which can substitute NADP+, can be used. Oxidised DCPIP (dark blue) is decolourised by photosynthesising tissues to reduced DCPIP (colourless). You are required to: • Investigate the rate of photosynthesis in different concentrations of commercially available chloroplast extracts from wild-type crop • Obtain a chloroplast extract from the transgenic crop • Estimate the concentration of chloroplasts in the chloroplast extract from the transgenic crop You are provided with: • 20 cm3 of commercially available wild-type crop containing 10% chloroplast extract, in a vial labelled V • Leaves from transgenic crop, L • Ice-cold buffer solution, in a large vial labelled C • A block of agar stained with DCPIP, A. DCPIP agar may stain your skin. You are advised to wear gloves. If any of these reagents come into contact with your skin, wash off immediately under cold water.

3 [Turn over] Anglo-Chinese Junior College H2 9477 Paper 4 Preliminary Examination For Examiner Use Proceed as follows. 1 You are required to perform a serial dilution of V to reduce the concentration of the provided chloroplast extract by a factor of ten between successive dilutions, VE2, VE3, VE4 and VE5. You will need to make up 10.0 cm3 of each solution. Some will be used to make the next solution such that the final volume in each vial is 9.0 cm3. Fig. 1.1 shows you the first two beakers you will use to make your serial dilution. (ii) Complete Fig. 1.1 by drawing as many extra vials as you need for your serial dilution. For each vial: • state, under the vial, the final volume and concentration of VE2, VE3, VE4 and VE5 obtained to be used in the investigation • use one arrow with a label, above the vial, to show the volume and concentration of VE1, VE2, VE3, VE4 and VE5 added to perform the serial dilution • use another arrow with a label, above the vial, to show the volume of distilled water W added to prepare the concentration [4] Fig. 1.1 1. Correct volumes of water (W) and chloroplast extract (VE) added; 2. Correct concentrations of chloroplast extract; 3. Correct precision; 4. Removing 1 cm3 of VE5

4 Anglo-Chinese Junior College H2 9477 Paper 4 Preliminary Examination For Examiner Use (iii) Suggest an advantage of carrying out serial dilution. 1. Ability to make small concentrations – not possible with simple dilution as volumes of stock will be too small to be measured accurately with the provided apparatus; 2. Ability to test a wider range of concentrations; 3. Volume of stock solution needed is small; 4. Larger difference in concentration between intervals, able to record observable change in area of DCPIP decolourised R! serial dilution is more accurate / easier to measure than proportional dilution [1] 2 Label five vials, VE1, VE2, VE3, VE4 and VE5. Use them to prepare the different concentrations according to your answers in 1(a)(ii). 3 Place the block of DCPIP-stained agar onto a white tile. Using a ruler and a knife, cut the agar block into identical cubes of 10 mm x 10 mm x 10 mm, as shown in Fig. 1.2. Fig. 1.2 Choose an appropriate number of cubes that are sufficient for the subsequent steps. 4 Obtain 5 pieces of 3.0 cm x 3.0 cm of fresh leaves from L. 5 Using a white tile and knife, chop up these 5 pieces of 3.0 cm x 3.0 cm leaves. 6 Transfer the chopped pieces of leaves into the mortar. 7 A total of 15.0 cm3 of ice-bold buffer solution C should be added to the mortar. Add this slowly in 5.0 cm3 portions, grinding the leaf pieces in the buffer after each addition. (iv) Suggest why ice-cold buffer should be used to extract chloroplasts. 1. Prevent enzyme denaturation to maintain chloroplast activity; 2. Ensure chloroplast remains intact; 3. Inactivates enzymes, preventing/reducing photosynthesis; R! pH buffer R! disrupts membrane / cell wall, for easier extraction of chloroplasts [1] 10 mm 10 mm 10 mm

5 [Turn over] Anglo-Chinese Junior College H2 9477 Paper 4 Preliminary Examination For Examiner Use 8 Decant and filter the mixture into a test tube. The filtrate will be the leaf extract, LE. 9 Transfer 9.0 cm3 of LE into a new vial. 10 Label this vial, LE. (v) A piece of aluminium foil could have been used to cover the vial containing LE. Suggest why this is important. To minimize exposure to light so that photosynthesis does not start before experiment starts ensuring that subsequent measurements made are accurate. R! prevent / reduce CO2 / O2 from entering R! prevent / reduce evaporation of the buffer [1] 11 Transfer a piece of the agar cube using a pair of forceps into the small vial containing VE1. Leave the agar cube in VE1 for 10 minutes. 12 Repeat step 11 for VE2, VE3,