VJC 2021 H2 Bio 9744 P4 QP

VICTORIA JUNIOR COLLEGE JC 2 PRELIMINARY EXAMINATION 2021 HIGHER 2 NAME : ……………………………………………………….………………. CT CLASS: ………………..……… BIOLOGY Paper 4 Practical 9744 / 04 02/09/2021 2 hours 30 minutes Candidates answer on the Question Paper. No Additional Materials are required. READ THESE INSTRUCTIONS FIRST Write your name and CT in all the work handed 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 bracket [ ] at the end of each question or part question. Shift Laboratory Question Marks 1 2 Total This document consists of 12 printed pages. [Turn over]

1 Answer all questions. 1 You should read through the whole of this question carefully before you start your investigation. Betalains are red pigments that are found in some fungi and flowering plants, including beetroot, Beta vulgaris. Betalains are glycosides consisting of a glucose molecule bound to a pigment compound by a glycosidic bond. Cells of B. vulgaris store molecules of betalain in their vacuoles. The membrane surrounding vacuoles in plant cells is the tonoplast, which has a similar structure to other cell membranes. (a) (i) Suggest why betalain molecules cannot pass from vacuoles of plant cells into the cytoplasm. …………............................................................................................................................................... …………............................................................................................................................................... …………............................................................................................................................................... …….................................................................................................................................................. [2] Various factors influence the permeability of membranes. You are required to investigate the effect of different concentrations of alcohol on the membrane permeability of root cells of B. vulgaris. You are provided with: • 3 cores of beetroot tissue in a beaker of distilled water • 100% alcohol • 10.0% betalain solution • 1.0% betalain solution • distilled water Alcohol is highly flammable and harmful. You are recommended to wear eye protection. Ensure that there is no naked flame. Proceed as follows. 1 Cut the cores of beetroot tissue into discs of approximately 4 mm thickness. You will need at least 12 discs for the experiment. 2 Wash these discs thoroughly in several changes of washing water. Leave the discs in distilled water while you prepare the solutions of alcohol. (ii) Why were beetroot discs washed several times before they were used? …………............................................................................................................................................... …….................................................................................................................................................. [1]

2 3 Use the 100% alcohol to make solutions of different concentrations of alcohol. You will need 5.0 cm3 of each concentration to be placed into separate plastic vials for this investigation. (iii) State the concentrations of alcohol that you will use in your investigation. …………............................................................................................................................................... …….................................................................................................................................................. [1] (iv) Use the space provided below to show, in a suitable format, how you prepared the different concentrations of alcohol. [4] 4 Place two washed discs of beetroot tissue into the plastic vials containing the different concentrations of alcohol and cap them. Leave them for at least twenty minutes before taking results. Meanwhile continue with step 5. (v) State and explain a step that you can take in the preparation of the discs to ensure that you obtained valid results in this investigation. …………............................................................................................................................................... …………............................................................................................................................................... …………............................................................................................................................................... …….................................................................................................................................................. [2]

3 5 Make up a series of standard solutions of betalain using the 10.0% betalain solution, the 1.0% betalain solution and distilled water, as shown in Table 1.1. You will need to make 10.0 cm3 of each standard solution in the test-tubes provided. Table 1.1 concentration of standard solution of betalain/ % volume of 10.0% betalain solution / cm3 volume of 1.0% betalain solution / cm3 volume of distilled water / cm3 10.0 10.0 – 0.0 5.0 5.0 – 5.0 1.0 – 10.0 0.0 0.5 – 5.0 5.0 0.1 – 1.0 9.0 0.0 – – 10.0 6 After twenty minutes, pour off the solution from each plastic vial (from step 4) into an appropriately labelled test -tube. Compare the colour of these solutions with the standard solutions of betalain using the white card provided and estimate the concentration of betalain in each solution. (vi) Use this space to record, in a suitable format, your results from step 6. [4]

4 (vii) Describe and explain your results. …………............................................................................................................................................... …………............................................................................................................................................... .............................................................................................................................................................. .............................................................................................................................................................. …………............................................................................................................................................... …………............................................................................................................................................... …………............................................................................................................................................... …….................................................................................................................................................. [3] (viii) Based on the apparatus and materials provided, explain how y ou would increase the confidence in your estimation for 100% alcohol. ………….......................................................................................................................