YIJC 2023 [H2] Prelim.P4 (QP)

@YIJC 9744/04/PE/2022 [Turn over YISHUN INNOVA JUNIOR COLLEGE JC2 PRELIMINARY EXAMINATION Higher 2 CANDIDATE NAME CG INDEX NO. H2 BIOLOGY 9744/04 29 Aug 2023 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your name and class in the spaces at the top of this page. Write in dark blue or black pen only. You may use a soft pencil for any diagrams or graphs. Do not use 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. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 25 2 12 3 18 Total 55 This document consists of 16 printed pages and 2 blank pages.

2 @YIJC 9744/04/PE/2023 [Turn over Answer all questions. 1 The enzyme amylase breaks down starch to form reducing sugars. It has been found that tea affects the activity of amylase. You will investigate the effect of different concentrations of tea extract on the breakdown of starch by amylase. You are provided with the materials shown in Table 1.1. Table 1.1 label contents hazard volume / cm3 E amylase solution harmful irritant 30 T1 100% tea extract none 20 S starch solution none 50 W distilled water none 150 iodine iodine solution irritant 20 If any solution comes into contact with your skin, wash off immediately with cold water. It is recommended that you wear suitable eye protection. You will need to carry out a serial dilution of the 100% tea extract, T1, to reduce the concentration by half between each successive dilution. You are required to make up a sufficient volume of each tea extract so that, once the serial dilution has been completed, there is a volume of at least 5.0cm 3 for each concentration prepared. (a) (i) Complete Table 1.2 to show you will make the concentration of the tea extract T1, T2, T3, T4 and T5. Table 1.2 Tea extract T1 T2 T3 T4 T5 percentage concentration of tea extract 100 percentage concentration of tea extract to be diluted volume of the tea extract to be diluted / cm3 volume of distilled water W / cm3 [3]

3 @YIJC 9744/04/PE/2023 [Turn over Read steps 1 – 12. Proceed as follows. 1 Prepare the concentrations of tea extract as shown in Table 1.2. 2 Label the test-tubes with the concentrations you have prepared in step 1. 3 Put 1 cm 3 of each concentration of tea extract into the appropriately labelled test-tube. 4 Put 1 cm3 of E into each of the labelled test-tubes. Shake gently to mix. 5 Using the beakers labelled hot water and cold water, set up and maintain a water -bath with water between 30°C and 40°C. 6 Put the test-tubes from step 4 into the water-bath. 7 Label the two spotting plates, as shown in Fig. 1.1, with: • the times 2, 4, 6, and 8 (minutes) • the percentage concentrations of tea extract you have prepared in step 1. 8 Put drops of iodine solution onto the spotting tile as shown in Fig. 1.1. You will need one row of drops of iodine solution for each of the concentrations of tea extract you prepared in step 1. Fig. 1.1

4 @YIJC 9744/04/PE/2023 [Turn over 9 Put 2 cm3 of starch solution S into each test-tube (in the water-bath). Shake gently to mix. Start timing. 10 After 2 minutes: • use a pipette to remove a sample of the solution from the test-tube labelled 100%, • put 1 drop of the solution onto the spot of iodine solution labelled 2 (minutes) on the row labelled 100 (%), • put 1 drop of the next solution onto the spot of iodine solution labelled 2 (minutes) on the row labelled with your next concentration of tea extract, • repeat for the other concentrations of tea extract you prepared in step 1 , so that all of the drops of iodine solution in the 2-minute column have been used. 11 Repeat step 10 at intervals of 2 minutes until there is no blue-black colour. This is the endpoint. Note: you will not see the original colour of the iodine due to the colour of the tea extract. If the iodine continues to turn blue- black at 8 minutes, stop sampling and record this as ‘more than 8’. 12 Record in (a)(ii) the time taken to reach the endpoint. (ii) Record your results in an appropriate table. [4] (iii) State the trend for your results. [1]

5 @YIJC 9744/04/PE/2023 [Turn over (iv) Tea is a competitive inhibitor of amylase. Explain how tea can act as a competitive inhibitor of amylase. [3] (v) The volume of the drops of iodine solution in step 8 was not standardised. Suggest one improvement to step 8. [1] (vi) Identify two possible sources of error in step 9 and suggest improvements to reduce the effect of these errors. [4]

6 @YIJC 9744/04/PE/2023 [Turn over (b) Caffeine is a chemical found in tea and many other drinks. A student investigated the concentration of caffeine in different types of drink. Table 1.3 shows the student’s raw data and processed data. Table 1.3 type of drink raw data processed data volume of one serving /cm3 mass of caffeine per serving /mg concentration of caffeine / mg cm–3 black tea (BT) 220 40 0.18 filter coffee (FC) 350 195 decaffeinated tea (DT) 220 5 0.02 cola light (CL) 330 33 0.10 espresso coffee (EC) 30 48 1.60 green tea (GT) 220 18 0.08 (i) Complete Table 1.3 by calculating the concentration of caffeine in filter coffee. Show your working. [2]

7 @YIJC 9744/04/PE/2023 [Turn over (ii) Plot a suitable graph on the grid to show the concentration of caffeine (processed results) in the different types of drink shown in Table 1.3. [4] (c) (i) An energy drink contains a mixture of caffeine and reducing sugars. State the reagent you would use to determine the concentration of reducing sugar in the energy drink. [1] (ii) Describe how you would use the reagent in (c)(i) to determine the concentration of reducing sugar in the energy drink. [2] [Total: 25]

8 @YIJC 9744/04/PE/2023 [Turn over 2 The rate of photosynthesis can either be measured by the rate at which carbon dioxide is taken in or the amount of oxygen that is given out. During photosynthesis in leaves, carbon dioxide enters through the stomata and diffuses through intercellular air spaces to the mesophyll cells. Leaf discs submerged in sodium hydrogencarbonate solution can be used to investigate the effect of light intensity on photosynthesis. The rate of photosynthesis is measured by the time taken for the submerged discs to reach the surface when oxygen builds up in the air spaces. Using this information, design an experiment to investigate the effect of light intensity on photosynthesis in Camellia sinesis (tea) plant leaves. In your plan you must use: • bench lamp with 60 W bulb • 1% sodium hydrogencarbonate solution • C. sinesis (tea) leaves You may select from the following apparatus and use appropriate additional apparatus: • normal laboratory glassware, e.g. a variety of different sized beakers, measuring cylinders, and syringes • forceps • plastic straw • plastic ruler • retort stand • timer, e.g. stopwatch Your plan should: • have a clear and helpful structure such that the method you use is repeatable by anyone reading it • be illustrated by relevant diagram(s), if necessary • identify the independent and dependent variables • describe with scienti