HCI 2023 JC2 9744 H2 Bio Prelim P4 QP (Sharing)

© Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 4 HWA CHONG INSTITUTION JC2 Preliminary Examinations Higher 2 CANDIDATE NAME CT GROUP 22S7 __ CENTRE NUMBER INDEX NUMBER BIOLOGY Paper 4 Practical Candidates answer on the Question Paper. No Additional materials are required. 9744/04 28 August 2023 2 hours 30 minutes INSTRUCTIONS TO CANDIDATES There are two question booklets ( I and II) to this paper. Write your name, CT group, Centre number and index number in the spaces provided at the top of this cover page and on the lines provided at the top of the cover page of Booklet II. Answer all questions in the spaces provided on the question paper. Shift Laboratory INFORMATION FOR CANDIDATES 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. The number of marks is given in brackets [ ] at the end of each question or part question. You are reminded of the need for good English and clear presentation in your answers. This document consists of 23 printed pages and 1 blank page. For Examiners' Use 1 / 30 2 / 25 Total / 55

2 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 4 QUESTION 1 Part A The process of photosynthesis traps light using a range of pigments bound to chloroplast membranes. The development of these pigments and chloroplasts in young plants is influenced by their growth conditions. In this experiment you are required to investigate the pigments and chloroplasts in two sets of young plants, A and B, grown in different conditions. You must keep the two types of leaves separate throughout the investigation. Observe and make brief notes of any differences between a leaf from plant A and a leaf from plant B. Procedure 1 (To be attempted when you receive the light microscope) 1 Cut the leaves from specimen A into four pieces, each about 3 cm by 3 cm. Set aside two pieces of the leaves from specimen A for Procedure 2. 2 Place two pieces of the leaves from specimen A in a mortar. Add 4 cm3 distilled water and grind with a pestle for 1 minute. 3 Filter the suspension through the muslin cloth provided, onto a Petri dish. 4 Use the Pasteur pipette provided to put a drop of filtrate onto a microscope slide and cover with a coverslip. Observe under ×100 and ×400 magnifications. 5 Repeat steps 1 - 4 using the leaves from specimen B. (a) State two differences between the chloroplasts from specimen A and specimen B. [2] Procedure 2 6 Add 5 cm3 of ethanol into each of the two tubes labelled X provided. Label the tubes A and B respectively with a marker. 7 Put the cut pieces of leaves from specimen A and specimen B on separate clean paper towels. Remove any thick veins from the leaves. 8 Tear the cut pieces of leaves from specimen A into small pieces and place them into the corresponding tube of ethanol solution labelled A. Use a glass rod to push the leaves to the bottom of the tube. Place a stopper into the mouth of the tube.

3 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 4 9 Repeat step 8 using the cut pieces of leaves from specimen B and the corresponding tube of ethanol solution labelled B. 10 Place both tubes into a beaker. 11 Pour sufficient water from the 90 °C water bath into the beaker to reach the top of the extract in each tube. Incubate the tubes in the 90 °C water bath in the beaker for 10 minutes. Caution: Be careful when working with hot water. Continue with step 23 on pages 6 to 7 during this time. 12 Remove the tubes from the water bath carefully and allow to cool. 13 Remove the two strips of chromatography paper from the plastic bag and place on a clean paper towel. 14 Draw a pencil line 25 mm from one end of each piece of the chromatography paper. Label lightly in pencil one strip to use for extract A and the other to use for extract B. Caution: Do not draw the line with ink pen. 15 For each extract, use a micropipette tip to pick up a length of about 5 mm of the extract by using the tip to touch the surface of the extract. Apply a spot in the centre of the pencil line by touching it briefly against the centre of the pencil line. Allow it to dry and then apply another spot on top of the first spot. 16 Continue to apply spots until all the extract at the tip has been applied. Pick up another 5 mm of the extract and repeat step 15. 17 Fold the top of the paper 5 mm from the other end so that it is ready to be pinned to the underside of a boiling tube stopper. 18 Remove the stoppers from the top of the boiling tubes containing solvent. Pin the paper on the stopper and insert it into the boiling tube until the bottom of the paper just touches the solvent as shown in Fig.1.1. Make sure the paper does not touch the sides of the boiling tube. Caution: The solvent is flammable. Do not remove the stoppers from the boiling tubes if there are any lighted Bunsen burners or other flames in the room. Do not pour the solvent into the sink at the end of the experiment. Fig. 1.1 19 Leave the boiling tubes in a rack until the solvent front is almost at the fold. Do not move or shake the tubes during this time. Continue with step 23 on pages 6 to 7 while this is happening.

4 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 4 20 Remove the strips of paper from the boiling tubes . Mark in pencil the position of the solvent front and the front edge of each pigment immediately, since the colour of the pigments fades quickly. Leave to dry on a clean paper towel. (b) Prepare the space below to record your results in an appropriate format so that you can compare extract A with extract B . Include the R f value for each pigment calculated as instructed in step 21. [4] 21 Note the colour for each pigment you can see on each chromatogram. Work out their Rf values using the formula 𝑅𝑅𝑓𝑓 = 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑚𝑚𝑚𝑚𝑚𝑚𝑑𝑑𝑑𝑑 𝑏𝑏𝑏𝑏 𝑝𝑝𝑑𝑑𝑝𝑝𝑚𝑚𝑑𝑑𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓𝑚𝑚𝑚𝑚 𝑏𝑏𝑑𝑑𝑑𝑑𝑑𝑑 𝑙𝑙𝑑𝑑𝑑𝑑𝑑𝑑 𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑𝑑 𝑚𝑚𝑚𝑚𝑚𝑚𝑑𝑑𝑑𝑑 𝑏𝑏𝑏𝑏 𝑑𝑑𝑚𝑚𝑙𝑙𝑚𝑚𝑑𝑑𝑑𝑑𝑑𝑑 𝑓𝑓𝑓𝑓𝑚𝑚𝑚𝑚 𝑏𝑏𝑑𝑑𝑑𝑑𝑑𝑑 𝑙𝑙𝑑𝑑𝑑𝑑𝑑𝑑 You should measure to the front edge of each pigment. Record your results in the space you have prepared above.

5 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 4 22 Record in pencil on each chromatogram what you measured. (c) Label your chromatograms A and B and paste them in the space below using the sticky tapes provided. [1]

6 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations / Paper 4 (d)(i) Other than lack of replicates, suggest one source of error in this procedure and explain how it affects your results. [2] (d)(ii) Suggest an improvement that can be made to eliminate the error. [1] 23 In another part of this investigation, pigments were extracted from two more sets of young plants, A and B. The pigments were extracted as in P rocedure 2 and placed into a colourimeter to measure the absorbance of light using filters to find the absorbance at various wavelengths of light. The higher the absorbance, the more light is absorbed by the pigments. The results are shown in Table 1.1. Table 1.1 wavelength of light / nm absorbance of young plants A absorbance of young plants B 400 0.45 0.07 440 0.68 0.21 500 0.38 0.11 540 0.09 0.01 620 0.15 0.01 680 0.45 0.08 740 0.02 0.01

7 © Hwa Chong Institution 2023 9744 H2 Biology / JC2 Preliminary Examinations /