RVHS 2023 JC2 H2 Prelim P4 Question

RIVER VALLEY HIGH SCHOOL JC 2 PRELIMINARY EXAMINATION CANDIDATE NAME CENTRE NUMBER S CLASS INDEX NUMBER H2 BIOLOGY 9744/04 Paper 4 Practical 24 Aug 2023 Candidates answer on the Question Paper. 2 hours 30 minutes Additional Materials: As listed in the Confidential Instructions. READ THESE INSTRUCTIONS FIRST Write your Centre number, index number, class 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 an HB pencil for any diagrams or graphs. Do not use staples, paper clips, glue or correction fluid. DO NOT WRITE ON ANY BARCODES. 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 Examiner’s Use 1 2 3 Total This document consists of 21 printed pages and 3 blank pages.

2 River Valley High School 2023 JC2 Preliminary Examination H2 Biology 9744/04 Answer all questions. 1 Cells contain enzymes that catalyse metabolic activities. Some of these reactions release carbon dioxide. A scientist engineered a new strain of yeast, BY62, which he believes has higher rates of metabolic activities. You will investigate the release of carbon dioxide from mixtures of yeast and carbohydrate, one comprising a common yeast strain, Y , and the other comprising BY62. Each mixture is put into a dialysis (Visking) tubing. The dialysis tubing acts as a partially permeable membrane, allowing the carbon dioxide to diffuse out of the dialysis tubing. You are required to: • perform serial dilution to obtain different concentrations of P • collect results and present it in a suitable table • estimate the concentration of carbon dioxide in BY62 mixture You are provided with: • 1 g dried yeast, in a test-tube labelled Y • 10.0 % glucose solution, in a container labelled S • Mixture containing carbon dioxide produc ed from BY62 and carbohydrate , in a container labelled P • bromothymol blue indicator solution, in a container labelled B • dialysis tubing, in a beaker of distilled water labelled D • distilled water, in a beaker labelled W If any solution comes into contact with your skin, wash off immediately under tap water. Suitable eye protection should be worn. To test for the release of carbon dioxide, a sample of the water surrounding the dialysis tubing is added to drops of an indicator, B. Fig. 1.1 shows the effect of increasing concentration of carbon dioxide on the colour of B . Yellow is the end-point. BLUE blue-green GREEN green-yellow YELLOW Fig. 1.1 no carbon dioxide highest concentration of carbon dioxide

3 River Valley High School 2023 JC2 Preliminary Examination H2 Biology 9744/04 Before starting the investigation, read through steps 1 – 22 and prepare a table in (b)(i). Proceed as follows. 1 Using hot water and tap water, adjust the water in the beaker labelled water-bath to 45 °C. You will not need to maintain this temperature. 2 Put 15 cm3 of S into the test-tube labelled Y. Mix well. 3 Put test-tube Y into the water-bath for 15 minutes. You will leave the apparatus for 15 minutes. Use this time to continue with (a). (a) You are required to make a serial dilution of mixture in the container labelled P. P is obtained by subjecting yeast strain BY62 to the same conditions and experimental step 1 to step 3 as yeast strain Y. You are to reduce the concentration of P by five-fold between each successive dilutions. After the serial dilution is completed, you will need to have at least 8 cm3 of each concentration available for use. Complete Fig. 1.2 to show how you will dilute P. For each plastic vial: • state, under the plastic vial, the volume and concentration of P in the vial that will be available for use in the investigation, after the serial dilution has been completed • use one arrow, with a label above the plastic vial, to show the volume and concentration of P added to prepare the concentration of P in the vial • use another arrow, with a label above the plastic vial, to show the volume of distilled water, W, added to prepare the concentration of P in the vial. [2] Fig. 1.2 0 cm3 of W cm3 P cm3 P cm3 P ___ cm3 of W cm3 1 5 P

4 River Valley High School 2023 JC2 Preliminary Examination H2 Biology 9744/04 4 After 15 minutes, remove test-tube Y from the water-bath. 5 Stir the mixture in test-tube Y and pour it into a beaker. 6 Label two spotting tiles with the sample times in minutes, as shown in Fig. 1.3. 7 Put 3 drops of B onto the spotting tile at each sample time, as shown in Fig. 1.3. Fig. 1.3 sample time in minutes 3 drops of bromothymol blue solution, B

5 River Valley High School 2023 JC2 Preliminary Examination H2 Biology 9744/04 Fig. 1.4 shows the apparatus you will set up for this investigation. Fig. 1.4 8 Tie a knot in the dialysis tubing as close as possible to one end, so that the end is sealed. 9 To open the other end, rub the tubing gently between your fingers and thumb. 10 Stir the mixture in the beaker from step 5 and put 6.0 cm3 of this mixture into a syringe. 11 Wipe the outside of the syringe and put the mixture into the dialysis tubing. 12 Rinse the outside of the dialysis tubing with distilled water. 13 Repeat steps 8 to 12 using the final diluted concentration of mixture P obtained in (a). Look carefully at Fig. 1.4 to help you with step 14 to step 17 . You will be performing the following steps for both mixtures Y and P at the same time. 14 Tie a knot just above the level of the mixture in the dialysis tubing, as shown in Fig. 1.4. 15 Put the dialysis tubing into a clean boiling-tube so that it is resting on the bottom of the boiling-tube, as shown in Fig. 1.4. 16 Using a syringe, add 15 cm3 of distilled water, W, and ensure that each of the section of dialysis tubing containing the mixtures for Y and P is fully submerged. 17 Draw a line on the boiling-tube so that it is half-way between the two knots, as shown in Fig. 1.4. This is where you will take your samples from. 18 Start timing and put the boiling- tubes containing the dialysis tubing into the beaker labelled water-bath. 19 Take a sample of W from the boiling- tube at the point you marked in step 16, using a pipette. 20 Put 4 drops of W onto B at time 0 on the spotting tile. Put the remaining W in the pipette back into the boiling-tube. 21 Mix the sample of W and B on the spotting tile and immediately record the colour in (b)(i), using the colours stated in Fig. 1.1. 22 Repeat steps 19-21 for each of the sampling times until the end-point (yellow) is reached for two consecutive samples. If the end-point is not reached at 10 minutes, stop timing. boiling-tube boiling-tube

6 River Valley High School 2023 JC2 Preliminary Examination H2 Biology 9744/04 (b) (i) Record your results in a suitable table. [4] Table 1.1 shows the concentration of carbon dioxide present in a mixture if the end-point was detected at the sampling time. Table 1.1 sampling time / minutes 1 2 3 4 5 6 7 8 9 10 concentration of carbon dioxide in mixture / mol dm-3 4.6 2.1 1.4 0.9 0.6 0.2 0.07 0.039 0.005 0.001 (ii) Using your results in (b)(i), estimate the concentration of carbon dioxi