DHS 2023_H2 Biology_Prelim_Practical_ans

© DHS 2023 9744/04 [Turn over Name: Centre/Index Number: Class: DUNMAN HIGH SCHOOL Preliminary Examination Year 6 H2 BIOLOGY Paper 4 Practical Candidates answer on the Question Paper 9744/04 29 August 2023 2 hours 30 minutes READ THESE INSTRUCTIONS FIRST Write your centre number, index number, name and class at the top of this page. 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. The number of marks is given in brackets [ ] at the end of each question or part question. Shift Laboratory For Examiner’s Use 1 23 2 13 3 19 Total 55 This s consists of 15 printed pages (including this cover page) and 1 blank page.

2 © DHS 2023 9744/04 BLANK PAGE

3 © DHS 2023 9744/04 [Turn over 1 Enzyme E catalyses the hydrolysis of starch to maltose. The progress of this enzyme‑catalysed reaction can be followed by measuring the time taken for the substrate, starch, to disappear. You will investigate the effect of compound C, C1, on the hydrolysis of starch. If any solution comes into contact with your skin, wash off immediately under cold water. You will need to dilute the 2.0% compound C solution, C1, which reduces the concentration by a factor of ten between four successive dilutions, to give C2, C3, C4 and C5. Once the dilution has been completed, there is a volume of 10.0 cm3 for each solution in each vial. (a) (i) Complete Table 1.1 to show how you will make the concentrations of the compound C solutions, C2, C3, C4 and C5. Table 1.1 Label of compound C solution Percentage concentration of compound C solution Label of compound C solution to be diluted Volume of compound C solution to be diluted / cm3 Volume of distilled water to make up the dilution / cm3 Total volume / cm3 C1 2.0 10.0 0.0 10.0 C2 0.2 C1 1.0 9.0 10.0 C3 0.02 C2 1.0 9.0 10.0 C4 0.002 C3 1.0 9.0 10.0 C5 0.0002 C4 1.0 9.0 10.0 [3] (ii) Describe a suitable control for the experiment and explain its purpose. …........................................................................................................................................... …........................................................................................................................................... …........................................................................................................................................... . .......................................................................