VJC 2021 H2 Bio 9744 P4 CI

BIOLOGY 9744/04 Paper 4 Practical 2 September 2021 CONFIDENTIAL INSTRUCTIONS Great care should be taken to ensure that any confidential information given does not reach the candidates either directly or indirectly. Each candidate must be provided with the following apparatus and materials. Question 1 Each candidate will require, for a period of at least 90 minutes: 1. At least 20 cm3 of each of a 10% and a 1% betalain solution. A stock betalain solution should be prepared as follows: Peel and cut up 200 g of raw (uncooked) beetroot and liquidise with 100 cm3 of distilled water. Pour the homogenate through several layers of muslin. The following procedures can be scaled up according to the number of candidates. Preparing 40 cm3 of 10% betalain solution: 4 cm3 of the stock betalain solution should be used to make a 10% betalain solution, as follows: Add 4 cm3 of stock betalain solution to 36 cm3 distilled water and mix. This should be provided to the candidates in a 50 cm3 beaker, or other suitable container, labelled 10.0% betalain solution. Preparing 40 cm3 of 1% betalain solution: 4 cm3 of the 10% betalain solution should be used to make a 1% betalain solution, as follows: Add 4 cm3 of 10% betalain solution to 36 cm3 distilled water and mix. This should be provided to the candidates in a 50 cm3 beaker, or other suitable container, labelled 1.0% betalain solution. 2. Three cores of raw (uncooked) beetroot tissue with a minimum length of 3 cm. These should be prepared as follows: Peel the beetroot. Use a size 6 cork borer to make several cores of beetroot tissue. The direction of the cores is not important and depends on the size of the individual beetroot. There is no need to trim the ends of the cores so that they are at right angles. Provide the cores to the candidates in a beaker and cover with distilled water. 3. [F][MH][HH] 50 cm 3 of 100% alcohol (IMS / IDA) in a capped bottle labelled 100% alcohol , flammable. 4. Six plastic vials with caps (at least 10 cm3 capacity) 5. 200 cm3 distilled water in a capped plastic vial labelled distilled water 6. 250 cm3 beaker labelled tap water (also used in Q2) 7. 12 test-tubes (15 mm × 150 mm) (also used in Q2) 8. Rack or racks to contain at least 12 test-tubes (also used in Q2)

2 9. Three 10 cm3 syringes 10. Two 1 cm3 syringes. 11. Scalpel (e.g. Swann-Morton No. 11) or single-edged razor blade 12. White tile 13. Blunt forceps 14. Stirring rod 15. Plastic ruler (also used in Q2) 16. Marker pen 17. A piece of plain white card (to help determine colour intensity), approximately 10 cm × 10 cm 18. Stopwatch 19. Beaker for waste, labelled waste 20. Eight paper towels 21. Protective gloves 22. Eye protection Extra supplies of beetroot cores, plastic vials with caps, test-tubes, beakers, distilled water and 100% alcohol should be available if candidates request them.

3 Question 2 1) 25 cm3 of 0.1% 2,6 -dichlorophenol indophenol (DCPIP) solution in a covered, labelled plastic vial. Label as DCPIP. 2) 15 cm3 of each of four standard solutions of ascorbic acid prepared as follows: Dissolve 400 mg of ascorbic acid powder in 100 cm 3 distilled water. Add 15 drops of BDH Universal Indicator solution and adjust the pH to between 7 and 8 by adding 5% sodium hydroxide solution drop by drop. This is 4.0mgcm-3 ascorbic acid solution. Take 50 cm 3 of this solution and to it, add 50cm 3 of distilled water (the 2.0mgcm-3 ascorbic acid solution). Repeat this procedure to obtain 1.0mgcm-3 and 0.5mgcm-3 ascorbic acid. Any variations in the colours of the solution can be ignored, but the pH of the most dilute solution should be checked with indicator paper. If it is found to be below 7 it should be adjusted to pH 7 -8 by adding further drops of 5% sodium hydroxide solution. The solution should be dispensed to students in a covered, labelled plastic vials. Labels as such: 4.0, 2.0, 1.0, 0.5 respectively 3) 15 cm3 of fresh carrot juice. Dispense to students in covered plastic vial labelled C. Each candidate will have sole, uninterrupted use of a microscope for 1 hour 15 minutes only. Each candidate is provided with: 1. Microscope 2. TSF slide 3. Plastic ruler (also used in Q1) 4. test-tube rack(s) (also used in Q1) 5. 250 cm3 beaker labelled tap water (also used in Q1) 6. Five test tubes (also used in Q1) 7. Six 5 cm3 syringes (in plastic bag) 8. Sticky labels (in plastic bag) 9. Paper towel (in plastic bag) 10. 15 cm3 of carrot juice extract labelled C (in plastic vial) 11. 15 cm3 each of 4.0, 2.0, 1.0, 0.5 mgcm3 ascorbic acid solutions (in plastic vials) 12. 25 cm3 of DCPIP (in plastic vial)